Development of Multi-crystalline Silicon Ingot Technologies

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中科院半导体所科技成果——III-V化合物半导体单晶生长和晶片加工技术

中科院半导体所科技成果——III-V化合物半导体磷化铟(InP)、锑化镓（GaSb）和砷化铟（InAs）单晶生长和晶片加工技术项目成熟阶段成熟期成果简介InP单晶片主要作为衬底材料外延生长各种微波器件用微结构外延材料（如HEMT、HBT）和大功率激光器等的多量子阱材料，主要应用领域包括移动通信、卫星通信、导航、光纤通信、高效太阳能电池等。

InAs单晶片主要作为衬底材料，制造波长2-14µm的红外发光管、激光器等，GaSb单晶片衬底用于制造2-5µm波长的室温连续波激光器。

这些红外器件在气体监测、低损耗光纤通信、红外成像探测技术等领域有良好的应用前景。

GaSb单晶还是制造热光伏器件的理想材料，已应用在工业余热发电、便携发电设备等。

InAs单晶还用于制造霍耳器件、产生太赫兹波等。

2英寸和3英寸直径（100）InP单晶2英寸和3英寸直径（100）GaSb单晶2英寸和3英寸直径（100）InAs单晶照片技术特点InP、GaAs、GaSb和InAs单晶的生长方法为液封直拉法（LEC）。

生长出的单晶需要经过定向切割成为厚度为0.5-0.8毫米左右的标准圆片（直径2英寸、3英寸等），然后进行抛光、腐蚀和清洗后，在超净条件下包装密封，即可作为商品提供给用户使用。

主要生产工艺流程晶体生长→晶锭滚圆→定向切割→晶片研磨→抛光→清洗腐蚀→超净封装→用户。

市场分析目前市场价格为：2英寸片1000-1500元/片，3英寸片2000-3000元/片。

合作方式技术服务产业化所需条件主要生产加工设备：高压单晶炉：主要用于InP和InAs的多晶合成和单晶生长；常压单晶炉（相当于40型或更大的Si单晶炉）：用于GaSb单晶、InAs单晶和InSb单晶的生长；内圆切割机和多线切割机：用于单晶的定向和晶片切割；研磨机：晶片研磨；抛光机：晶片的单面和双面抛光；其它配套条件：超净厂房、晶片的清洗腐蚀设备、表面检测分析和常规电学测试设备等。

晶态IGZO_薄膜晶体管的研究进展

第 38 卷第 8 期2023 年 8 月Vol.38 No.8Aug. 2023液晶与显示Chinese Journal of Liquid Crystals and Displays晶态IGZO薄膜晶体管的研究进展姜柏齐1，刘斌1，刘贤文1，张硕1，翁乐1，史大为2，郭建2，苏顺康2，姚琪3，宁策3，袁广才3，王峰1，喻志农1*（1.北京理工大学光电学院，北京市混合现实与先进显示技术工程研究中心，北京 100081；2.重庆京东方显示技术有限公司，重庆 400714；3.北京京东方显示技术有限公司，北京 101520）摘要：随着显示技术的不断发展，对高性能、高稳定性的薄膜晶体管（Thin Film Transistor，TFT）的需求日趋增加，通过结晶改善薄膜晶体管性能的方法受到大量关注。

当前，铟镓锌氧化物（IGZO）材料由于具有迁移率高、柔性好、透明度高等优势，被广泛用于薄膜晶体管的沟道中，而改善IGZO沟道层的结晶形态也成为研究热点。

本文总结了晶态IGZO薄膜晶体管器件的研究进展，详细介绍了IGZO系化合物的晶体结构，重点阐述了单晶、c轴取向结晶、六方多晶型、尖晶石型、纳米晶型和原生结晶型IGZO的结构和各晶态IGZO薄膜晶体管的制备方法、器件性能和稳定性，深入分析其微观结构，总结物理特性，阐述不同晶系结构的结晶机理，建立不同晶体结构与电学特性的关系，最后对晶态IGZO薄膜晶体管的发展进行展望。

关键词：晶态IGZO薄膜；薄膜晶体管；晶体结构；研究进展中图分类号：TN321+.5 文献标识码：A doi：10.37188/CJLCD.2023-0121Research progress on crystalline IGZO thin film transistor JIANG Bai-qi1，LIU Bin1，LIU Xian-wen1，ZHANG Shuo1，WENG Le1，SHI Da-wei2，GUO Jian2，SU Shun-kang2，YAO Qi3，NING Ce3，YUAN Guang-cai3，WANG Feng1，YU Zhi-nong1*（1.School of Optics and Photonics， Beijing Engineering Research Center of Mixed Reality and Advanced Display， Beijing Institute of Technology， Beijing 100081， China；2.Chongqing BOE Display Technology Co.， Ltd.， Chongqing 400714， China；3.Beijing BOE Display Technology Co.， Ltd.， Beijing 101520， China）Abstract： With the development of display technology， the demand for high-performance and high-stability thin film transistors （TFTs） is increasing. The method of improving the performance of thin film transistors through crystallization has received a lot of attention. Currently， indium gallium zinc oxide （IGZO） materials are widely used in the channels of thin film transistors due to their advantages such as high mobility， flexibility，and high transparency. Improving the crystalline morphology of the IGZO channel layer has become a research hotspot.This article summarizes the research progress of crystalline IGZO thin film transistor devices，文章编号：1007-2780（2023）08-1031-16收稿日期：2023-04-04；修订日期：2023-05-10.基金项目：国家重点研发计划（No.2021YFB3600703）Supported by National Key Research and Development Program of China（No.2021YFB3600703）*通信联系人，E-mail： znyu@第 38 卷液晶与显示introduces in detail the crystal structure of IGZO compounds， and focuses on the structure of single crystalline，c-axis-aligned crystalline，hexagonal polycrystalline，spinel，nanocrystalline，and protocrystalline IGZO，as well as the preparation methods，device performance，and stability of various crystalline IGZO thin-film transistors.We also analyze the microstructure of crystalline IGZO，summarize the physical properties，describe the crystallization mechanism and establish the relationship between crystal structure and electrical properties. At last， the development of crystalline IGZO thin film transistor is prospected.Key words： crystalline IGZO film； thin film transistor； crystal structure； research progress1 引言薄膜晶体管（TFT）是使用半导体材料制成的绝缘栅极场效应管。

硅太阳能电池表面陷光结构

硅太阳能电池表面陷光结构研究摘要众所周知，化石能源等一次能源短缺的问题日益凸显，化石能源的燃烧伴随着大量有害物质的排放，危害人类身体健康，造成酸雨的形成，严重污染水土等。

作为太阳能利用的重要组成部分，光伏发电是一种清洁的、用之不竭的可再生绿色新能源，受到越来越多的关注。

近年来全球光伏产业发展速度迅猛，而我国光伏产业规模已经稳居全球第一。

但是，国内相关的科学研究还很缺乏，技术积累薄弱，阻碍了光伏产业的进一步发展。

因此，开展此方面的基础研究具有重要的科学意义和应用价值。

目前，晶体硅（包括单晶硅、多晶硅和带硅等）太阳电池占光伏产业市场份额的90%以上，在2020年之前，晶体硅太阳电池的统治地位难以撼动。

由于硅材料成本居高不下，减薄硅片厚度成为降低电池生产成本最有效的手段。

在硅片变薄的同时，对光吸收效率和表面钝化的要求也增加了。

增强光吸收对保持薄片晶体硅太阳电池的性能稳定和进一步提升转换效率十分重要。

围绕晶体硅太阳电池的光吸收问题，本文进行了一系列研究，包括金字塔表面陷光结构和多孔硅结构的制备方法和工作机理，多孔-金字塔结构的制备及性能研究，得出了如下结论：THE RESEARCH OF SURFACE LIGHT TRAPPINGSTUCTURE OF SILICON SOLAR CELLABSTRACTAs we all know, fossil energy and other Primary energy shortage Problem has become in creas in gly Prominent, the bur ning of fossil fuels along with a large nu mber of emissi ons. of harmful substa nces, harm to huma n health, result ing in the formati on of acid rain serious Polluti on of water and soil. As a clea n and in exhaustible reProducible gree n energy,Photovoltaics(P W is an imPortant Part of the utilization of solar energy and has draw n exte nsive atte ntio n PV market and corelative aPPlicati on in creased drastically In China, a world-shaking growth of PV industry has been witnessed The outPut had been the first in the world since 2007. However,domestic studies on relative scienee are still short and tech no logy accumulati ons are relatively devoid The lack of tech no logy hin ders the further develoPment of PV industry. Therefore, basic studies on PV have imPerative scie ntific sig nifica nee and aPPlicati on valuePrese ntly,crystalli ne silic on solar cells which acco unts for more tha n 9% ofall kinds of solar cells are the dominator of PV market. According to a matter of sPeculation, crystalline silicon solar cells will still be the dominator of PV market before 2020. Because of the high cost of silicon materials, silicon wafers are getting thinner and thinner for effective cost reducti on. Utilizatio n of thin wafer in creases the request for light absorPti on and surface Passivation. Light absorPtion is imPerative to keeP the ProPerty of silicon solar cells stable and to conv eBi on efficie ncy1绪论1.1硅太阳能电池的研究背景及意义硅太阳电池是最常用的卫星电源，从1970年代起，由于空间技术的发展，各种飞行器对功率的需求越来越大，在加速发展其他类型电池的同时，世界上空间技术比较发达的美、日和欧空局等国家，都相继开展了高效硅太阳电池的研究。

突破：二维半导体异质结研究获新进展

突破：二维半导体异质结研究获新进展最近，中科院半导体所超晶格国家重点实验室博士生康俊，在李京波研究员、李树深院士和夏建白院士的研究团队中，与美国劳伦斯伯克利国家实验室(LBNL)汪林望博士研究组合作，在二维半导体异质结的基础研究中取得新进展。

相关成果发表在2013年9月30日美国化学学会主办的《纳米快报》(NanoLetters)上。

半导体异质结是由不同半导体材料接触形成的结构。

由于构成异质结的两种半导体材料拥有不同的禁带宽度、电子亲和能、介电常数、吸收系数等物理参数，异质结将表现出许多不同于单一半导体材料的性质。

在传统半导体领域，以半导体异质结为核心制作的电子器件，如光电探测器、发光二极管、太阳能电池、激光器等，往往拥有比单一半导体材料制作的同类器件更加优越的性能。

近年来，以二维二硫化钼(MoS2)、二硒化钼(MoSe2)为代表的新型二维半导体材料迅速成为材料科学领域的研究前沿。

这类半导体的厚度仅为数个原子，并且有望成为新一代电子器件的二维平台。

将不同的二维半导体层堆积起来便形成了二维半导体异质结，而这类异质结中的新奇物理现象也成为了目前国际纳米科学研究的一个焦点。

在这种背景下，半导体所与LBNL的研究小组应用第一性原理计算，研究了二维MoS2/MoSe2异质结的结构和电子性质。

二维MoS2和MoSe2单层存在4.4%的晶格失配。

通过对应变能和结合能的计算发现，它们之间范德瓦尔斯结合作用的强度不足以消除这一失配形成晶格匹配的异质结，而是形成一种被称为莫氏图样(MoiréPattern)的结构。

在莫氏图样中，不同区域的MoS2和MoSe2的堆积方式也不同，进而导致不同区域的层间耦合作用及静电势不同，这将会对异质结的电子结构产生显著影响。

为了进一步探索莫氏图样。

Recent development of in silico molecular modeling for gas and

Available online at Recent development of in silico molecular modeling for gas and liquid separations in metal–organic frameworksJianwen JiangAs a new family of nanoporous materials,metal–organic frameworks(MOFs)are considered versatile materials for widespread applications.Majority of current studies in MOFs have been experimentally based,thus little fundamental guidance exists for the judicious screening and design of task-speciﬁc MOFs.With synergistic advances in mathematical methods,computational hardware and software,in silico molecular modeling has become an indispensable tool to unravel microscopic properties in MOFs that are otherwise experimentally inaccessible or difﬁcult to obtain.In this article,the recent development of molecular modeling is critically highlighted for gas and liquid separations in MOFs.Bottom-up strategies have been proposed for gas separation in MOFs,particularly CO2capture.Meanwhile, interest for liquid separation in MOFs is growing and modeling is expected to provide in-depth mechanistic understanding. Despite considerable achievements,substantial challenges and new opportunities are foreseeable in more practical modeling endeavors for economically viable separationsin MOFs.AddressDepartment of Chemical and Biomolecular Engineering,National University of Singapore,117576,SingaporeCorresponding author:Jiang,Jianwen(chejj@.sg)Current Opinion in Chemical Engineering2012,1:138–144This review comes from a themed issue onNanotechnologyEdited by Hua Chun ZengAvailable online23rd December20112211-3398/$–see front matter#2011Elsevier Ltd.All rights reserved.DOI10.1016/j.coche.2011.11.002IntroductionDuring the past decade,metal–organic frameworks (MOFs)have emerged as a new family of nanoporous materials[1,2].In remarkable contrast to traditional inor-ganic zeolites,MOFs can be synthesized from various inorganic clusters and organic linkers,thus possess a wide range of surface area and pore size.More fascinatingly, the judicious selection of building blocks allows the pore volume and functionality to be tailored in a rational manner.With such salient features,MOFs are considered versatile materials for widespread potential applications [3,4]as illustrated in Figure1.Indeed,MOFs have been identiﬁed as a topical area in materials science and technology because of their implications for global and national economies[5].To date,thousands of MOFs have been synthesized in this vibrantﬁeld and several(Cu-BTC,ZIF-8,MIL-53,etc.) are commercially available under the trade name Basoli-te TM[6].However,massive research efforts on MOFs have been primarily based on experiments.It is impractical to search for task-speciﬁc MOFs by trial-and-error from inﬁnitely large number of possible candidates.Therefore, quantitative guidelines are desired for the high-throughput screening of enormous MOFs and the rational design of new MOFs towards practical applications.In this context, clear and deep microscopic understanding from a molecu-lar level is indispensable.With synergistic advances in mathematical methods,computational hardware and soft-ware,in silico molecular modeling has played an increas-ingly important role in unraveling microscopic properties in MOFs[7 ,8 ,9 ].Sophisticated modeling and simu-lation provide molecular insights that are experimentally intractable,if not impossible,thus elucidate underlying physics from bottom-up.Among many potential appli-cations of MOFs,separations are of central importance in chemical industry and have been actively investigated [10].In this article,the recent development of molecular modeling is critically highlighted for both gas and liquid separations in MOFs,and the foreseeable challenges and opportunities are discussed.Gas separationThe overwhelming majority of studies for gas separation in MOFs have been focused on CO2capture.This is because the combustion of fossil fuels produces a huge quantity of CO2emissions into the atmosphere.Carbon capture and sequestration is crucial to environmental protection and sustainable economy.As an essential pre-requisite,CO2has to be captured fromﬂue gas/ shifted syngas in post-/pre-combustion processes. Another important gas separation involving CO2is puri-ﬁcation of natural gas,in which impurities such as CO2 need to be separated to enhance calorie content.MOF adsorbentsMost synthesized MOFs are crystallites and tested as adsorbents for gas separation.Several reviews have sum-marized numerous experimental studies for CO2capture in MOF adsorbents[11–13].Nevertheless,nearly all these experiments examined the adsorption of pure gases (e.g.CO2,N2,CH4,and H2)due to the formidable difﬁculty associated with mixtures.By contrast,simu-lation can be readily used for single or multi-componentsystems.Thus,quantitative understanding of mixture adsorption in MOFs has been obtained,to a large extent,from simulation studies.Several bottom-up strategies as illustrated in Figure 2have been proposed to tune CO 2capture performance,for example,using speciﬁc MOFs with small pores,catenation,functionalization,ionic fra-meworks,exposed metals or metal doping.Yang and Zhong [14]simulated the adsorption of CO 2/CH 4/H 2mixture in two MOFs (IRMOF-1and Cu-BTC)and found pore size strongly affects separation efﬁciency.However,IRMOF-1and Cu-BTC do not possess iden-tical topology,leading to ambiguous interplay with the effect of pore size.In this regard,Babarao et al.[15]examined the separation of CO 2/CH 4mixture in isostruc-tural MOFs (Cu-BTC and PCN-60)and observed that the selectivity in Cu-BTC with small pores is nearly twice of that in PCN-60.This strategy of small pores is also reﬂected in framework catenation that can induce con-stricted pores and greater potential overlaps.For example,catenated IRMOF-13and PCN-6exhibit a larger selectivity for CO 2/CH 4mixture than non-cate-nated counterparts [15].An appealing strategy is to use ionic MOFs as demonstrated by Jiang and co-workers [16,17 ,18]for the separation of CO 2-containing mixtures.Simulation reveals that CO 2molecules are strongly adsorbed onto the ionic frameworks and nonframeworkions,and the predicted selectivity is signiﬁcantly higher than in neutral MOFs and many other nanoporous materials.On the other hand,Yazaydin et al.[19]screened a diverse set of 14MOFs for low-pressure CO 2capture from ﬂue gas combining simulation and experiment.The results show that M/DOBDC (M =Zn,Mg,Co or Ni)with high density of exposed metals strongly interact with CO 2.By physical and chemical doping,Xu et al.[20 ]estimated the separation of CO 2/CH 4mixtures in Li-modiﬁed MOF-5.Owing to the enhancement of electro-static potentials,adsorption selectivity was predicted to be much higher than in MOF-5.In a separate study,Lan et al.[21 ]simulated CO 2capture in covalent-organic frameworks doped by alkali,alkaline-earth and transition metals,and concluded that Li is the best surface modiﬁer for CO 2capture.The strategies outlined in Figure 2have been compre-hensively discussed [24 ,25 ].Two of them (ionic fra-meworks and metal doping)appear to be more efﬁcient to enhance CO 2capture.It should be noted that these strategies also can tune the separation of other mixtures,for example,the selectivity of alkane isomers was found to be enhanced by framework catenation [26].In a recent perspective,Krishna and van Baten [27 ]highlighted the potency of simulation in screening of best MOFs for CO 2capture and hydrocarbon separation,and they furtherRecent development of in silico molecular modeling Jiang 139Figure 1Purification Toxics RemovalDrug DeliveryFuel Cell SystemsStorageStorage and SeparationCarbon SequestrationSensingMOPWidespread potential applications of MOFs (/ees6/clathrates/index.shtml ).compared MOFs against traditional zeolites with regard to separation characteristics.As an alternative to simulation,analytical theories have been developed for gas separation in MOFs.Liu et al.[28,29]proposed a density functional theory (DFT)in 3D-nanoconﬁned space.The theory was applied to adsorption and separation in 3D-MOFs with complex pore networks,whereas most DFT studies are limited in simple conﬁned geometries (e.g.slit and cylindrical pores).Good agree-ment was obtained between theoretical predictions,simu-lation and experimental data.Coudert et al.[30]developed the osmotic framework adsorbed solution theory (OFAST)in terms of a competition between host’s free energy and adsorption energy.This theory is based exclusively on pure-component adsorption and has the superior capability to describe ﬂexible MOFs.For illustration,the authors used the OFAST to examine the effect of breathing on separation of CO 2/CH 4mixtures in MIL-53.The modeling studies discussed above for gas separation in MOF adsorbents are primarily focused on adsorption selectivity.However,several other factors (e.g.working capacity,regenerability,etc.)should be included in prac-tice as discussed by Bae and Snurr [31 ].Another crucial issue is how moisture in gas mixtures would affect sep-aration performance?From systematical simulation stu-dies in various neutral and ionic MOFs,Jiang and coworkers observed four different intriguing effects ofH 2O on CO 2capture [25 ].It is also instructive to examine structural change in ﬂexible MOFs that might occur upon adsorption [32].The incorporation of ﬂexi-bility to simulate structural change would need a robust force ﬁeld.However,a general force ﬁeld is currently unavailable for MOFs and ﬁrst-principles modeling is expected to play a pivotal role [33 ].In addition,the chemical and thermal stability of MOFs are important for separation [34].A large number of MOFs are unstable in atmosphere or under moisture,which impedes their util-ization.Therefore,it is indispensable to develop molecu-lar guidelines for the design of stable MOFs.Nevertheless,unraveling what govern the stability of MOFs at a microscopic level is a challenge.MOF membranesCompared with adsorptive separation,membrane-based separation is considered to be energetically more efﬁ-cient,lower capital cost and larger separation capability.However,the fabrication of MOF membranes is a for-midable task [35].Only in recent years,have there been active experimental endeavors to explore MOF mem-branes for gas separation [36 ].Since both equilibrium and dynamic properties are required,simulation for gas separation in MOF mem-branes is more time-consuming than in MOF adsorbents.Nevertheless,a handful of simulation studies have been reported.Keskin and Sholl [37 ]examined the separation140NanotechnologyFigure 2functionalizationmetal dopingionic frameworksexposed metalssmall porescatenationBottom-up strategies to tune CO 2capture performance.The representative MOFs are from [15,17 ,20 ,22,23].performance of diverse MOFs for CO2/CH4and CO2/H2 mixtures.They found that all the MOFs examined exhi-bit unfavorably low CO2selectivities and mixture effects play a crucial role in determining the performance.By combining simulation and IR microscopy,Bux et al.[38] simulated ethene/ethane separation in ZIF-8membrane. They found that ethane adsorbs more strongly than ethene,but ethene diffuses faster;and the interplay results in a membrane permeation selectivity for ethene. Krishna and van Baten[27 ]underlined the advantages of using simulation tools in the screening of MOF mem-branes for CO2capture.Along with considerable interest in MOF membranes, MOF-based composite membranes have received increasing attention for gas separation.In this emerging area,a handful of experiments have been conducted[39], but modeling studies are ing atomistic simulation and continuum model,Keskin and Sholl[40]attempted to select MOF/polymer membranes for high-perform-ance gas separation.A highly selective MOF was ident-iﬁed and predicted to enhance the performance of Matrimid and other polymers for CO2/CH4separation. Chen et al.[41]proposed a composite with ionic liquid (IL)supported on IRMOF-1.The simulation reveals that ions in the composite act as favorable sites for CO2adsorption,and the selectivity for CO2/N2mixture is higher than in neat IL,IRMOF-1and many other supported IL membranes.It is worthwhile to note that defects and inter-crystalline interstices usually exist in synthesized MOF membranes. Nevertheless,most simulation studies use perfect and rigid models for MOF membranes.How to incorporate defects and interstices into practical modeling is challenging.On the other hand,theﬂexibility of MOF structures may have a larger inﬂuence in membrane separation than adsorbent separation[36 ],and should be implemented as well into modeling.Another essential issue is the mech-anical properties of MOFs[42].The high pressure exerted for membrane separation may distort MOF structures and deteriorate performance.It is thus crucial to quantitatively understand how pressure affects pore geometries and framework dimensionalities.For MOF-based composite membranes,microscopic insights into the interactions between MOF and other species(e.g.polymer or ionic liquid)are strikingly important and fundamental studies at a molecular level are desired.Liquid separationWhile gas separation in MOFs has been extensively investigated,endeavors for liquid separation are lagged behind[43 ].A recent trend has been to explore the use of MOF adsorbents and membranes for liquid separation. By combining chromatographic and breakthrough exper-iments,Alaerts et al.determined the adsorption and separation of ortho-substituted alkylaromatics(xylenes, ethylbenzene,ethyltoluenes and cymenes)in a column packed with MIL-53crystallites[44].Jin and coworkers tested the separation of water/organics mixtures in MIL-53membrane and observed a high selectivity for water removal from ethyl acetate solution[45].Simulation for liquid separation in MOFs is scarce owing to the signiﬁcant amount of computational time required to sample liquid phase.Consequently,the microscopic understanding of liquid separation in MOFs is far from complete.To the best of our knowledge,only two simu-lation studies have been reported in this area,one for water desalination and the other for biofuel puriﬁcation. Recent development of in silico molecular modeling Jiang141Figure3Selectivities of biofuel in Na-rho-ZMOF and Zn4O(bdc)(bpz)2by pervaporation[47 ].Speciﬁcally,Hu et al.[46]performed simulation on the desalination of NaCl aqueous solution through a ZIF-8 membrane by reverse osmosis.Because of the sieving effect of small apertures in ZIF-8,Na+and ClÀions could not transport through ZIF-8membrane and water desa-lination was observed.Theﬂux of water permeating the membrane was found to scale linearly with external pressure.In a separate study,Nalaparaju et al.[47 ] examined hydrophilic Na-rho-ZMOF and hydrophobic Zn4O(bdc)(bpz)2for biofuel puriﬁcation.The selectiv-ities between water and ethanol in the two MOFs are largely determined by adsorption behavior.As indicated in Figure3,Na-rho-ZMOF is preferable to remove water, whereas Zn4O(bdc)(bpz)2is promising to enrich ethanol. The simulation provides molecular guidelines for the selection of appropriate MOFs towards efﬁcient biofuel puriﬁcation.Currently,modeling for liquid separation in MOFs is very limited.With increasing demands for clean water,liquid fuels and other liquid-based applications,more efforts are expected in order to provide deep molecular insights.A pre-requisite for liquid separation is that the MOFs used should be stable in water or other liquids[48],it is crucial to understand what factors govern the stability of MOFs, which would allow to produce stable MOFs for liquid separation.ConclusionAs a burgeoningﬁeld,research activities in MOFs are rather hectic.In addition to enormous experimental stu-dies,we have witnessed the recent development of in silico molecular modeling for MOFs.Microscopic under-standing has been achieved for gas separation particularly CO2capture in MOFs,and bottom-up strategies have been proposed to enhance separation efﬁciency.How-ever,liquid separation in MOFs remains largely unex-plored at a molecular level and more endeavors are desired towards this end.It is obvious that current molecular modeling for separ-ations using MOFs is still in an infant stage.As discussed above,substantial challenges are foreseen for more prac-tical modeling and precise description.A number of issues should be considered in future modeling,such as the stability and mechanical properties of MOFs, structuralﬂexibility,material regenerability,and effect of moisture(in gas separation).These challenges provide new opportunities for modeling studies to unravel in-depth microscopic insights and thus provide quantitative guidelines on the rational screening and design of novel MOFs.Furthermore,for energy-efﬁcient and cost-effec-tive separations,process requirements are essential to be integrated with material properties at a system level.In this context,molecular modeling,process optimization, as well as material synthesis,should be synergized holi-stically towards the development of best MOFs for economically viable separations and other practical appli-cations.AcknowledgementsThe author gratefully acknowledges the National University of Singapore, the Singapore National Research Foundation,and the Ministry of Education of Singapore for support.References and recommended readingPapers of particular interest,published within the period of review, have been highlighted as:of special interestof outstanding interest1.Yaghi OM,O’Keefe M,Ockwig NW,Chae HK,Eddaoudi M,Kim J:Reticular synthesis and design of new materials.Nature2003, 423:705-714.2.Long JR,Yaghi OM:The pervasive chemistry of metal–organicframeworks.Chem Soc Rev2009,38:1213-1214.3.MacGillivray LR(Ed):Metal–Organic Frameworks:Design andApplication.Hoboken,New Jersey:John Wiley&Sons,Inc.;2010.4.Farrusseng D(Ed):Metal–Organic Frameworks:Applications fromCatalysis to Gas Storage.Weinheim,Germany:Wiley-VCH;2011.5.Adams J,Pendlebury D:Global Research Report:MaterialsScience and 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Babarao R,Jiang JW:Unprecedentedly high selective adsorption of gas mixtures in rho zeolite-like metal–organic framework:a molecular simulation study.J Am Chem Soc 2009,131:11417-11425.A simulation study is reported for the separation of CO2-containingmixtures in rho zeolite-like MOF(ZMOF)with anionic framework.Fortheﬁrst time,this study characterizes nonframework Na+ions,examines gas separation in ionic ZMOF,and reveals that rho-ZMOF is a promisingcandidate for CO2capture.18.Babarao R,Eddaoudi M,Jiang JW:Highly porous ionic rhtmetal–organic framework for H2and CO2storage andngmuir2010,26:11196-11203.19.Yazaydin AO,Snurr RQ,Park TH,Koh K,Liu J,LeVan MD,Benin AI,Jakubczak P,Lanuza M,Galloway DB et al.:Screeningof MOFs for CO2capture fromﬂue gas using a combinedexperimental and modeling approach.J Am Chem Soc2009,131:18198-18199.20. Xu Q,Liu DH,Yang QY,Zhong CL,Mi JG:Li-modiﬁed metal–organic frameworks for CO2/CH4separation.J Mater Chem 2010,20:706-714.The separation of CO2/CH4mixtures is simulated in Li-modiﬁed MOF-5. The selectivity is found to be greatly improved owing to the enhancement of electrostatic potential by Li doping.21. Lan JH,Cao DP,Wang WC,Smit B:Doping of alkali,alkaline-earth,and transition metals in covalent-organic frameworks for enhancing CO2capture byﬁrst-principles calculations and molecular simulations.ACS Nano2010,4:4225-4237.This study examines the doping of a series of alkali(Li,Na,and K), alkaline-earth(Be,Mg,and Ca),and transition(Sc and Ti)metals in covalent-organic frameworks,and the effects of the doped metals on CO2capture.22.Dietzel PDC,Johnsen RE,Fjellvag H,Bordiga S,Groppo E,Chavan S,Blom R:Adsorption properties and structure of CO2 adsorbed on open coordination sites of metal–organicframework Ni2(dhtp)from gas adsorption.IR spectroscopyand X-ray diffraction.Chem Commun2008,44:5125-5127.23.Babarao R,Dai S,Jiang DE:Functionalizing porous aromaticframeworks with polar organic groups for high-capacity and selective CO2separation:a molecular simulation study.Langmuir2011,27:3451-3460.24. Liu DH,Zhong CL:Understanding gas separation in metal–organic frameworks.J Mater Chem2010,20:10308-10318.This feature article summarizes the recent advances of computer model-ing on gas separation in MOFs and demonstrates how computer model-ing can help to understand the separation characteristics of MOFs.Several strategies are proposed to improve the separation efﬁciency of MOFs.25. Jiang JW:Metal–organic frameworks for CO2capture:what are learned from molecular simulations.In Coordination Polymers and Metal Organic Frameworks.Edited by OO L,Ramı´rez LD.Nova Science Publishers;2011.In this book chapter,recent simulation studies are summarized for CO2 capture in MOFs.A number of strategies are discussed towards improv-ing capture performance.In addition,the effects of moisture in various MOFs on CO2adsorption and separation are presented.26.Babarao R,Tong YH,Jiang JW:Molecular insight intoadsorption and diffusion of alkane isomer mixtures in metal–organic frameworks.J Phys Chem B2009,113:9129-9136.27. Krishna R,van Baten JM:In silico screening of metal–organic frameworks in separation applications.Phys Chem Chem Phys 2011,13:10510-10593.This perspective highlights the potency of molecular simulation in deter-mining the best MOF for a given separation task.A variety of metrics that quantify separation performance such as adsorption selectivity,working capacity,diffusion selectivity and membrane permeability are determined by simulation.28.Liu Y,Liu HL,Hu Y,Jiang JW:Development of a densityfunctional theory in three-dimensional nanoconﬁned space:H2storage in metal–organic frameworks.J Phys Chem B2009, 113:12326-12331.29.Liu Y,Liu HL,Hu Y,Jiang JW:Density functional theory foradsorption of gas mixtures in metal–organic frameworks.J Phys Chem B2010,114:2820-2827.30.Coudert FX,Mellot-Draznieks C,Fuchs AH,Boutin A:Predictionof breathing and gate-opening transitions upon binary mixture adsorption in metal–organic frameworks.J Am Chem Soc2009,131:11329-11331.31.Bae YS,Snurr RQ:Development and evaluation of porousmaterials for carbon dioxide separation and capture.AngewChem Int Ed2011,50:11586-11596.The question of how a large number of MOFs can be quickly evaluated for CO2separation is addressed.Five adsorbent evaluation criteria are described and used to assess over40MOFs for their potential in CO2 separation processes for natural gas puriﬁcation,landﬁll gas separation, and CO2capture from power-plantﬂue gas.32.Horike S,Shimomura S,Kitagawa S:Soft porous crystals.NatChem2009,1:695-704.33.Taﬁpolsky M,Amirjalayer S,Schmid R:Atomistic theoreticalmodels for nanoporous hybrid materials.MicroporousMesoporous Mater2010,129:304-318.Available atomistic theoretical models are overviewed for the new class of functional porous hybrid materials such as MOFs and COFs.The current status of both periodic and non-periodic quantum mechanic,as well as molecular mechanic models are discussed.34.Kang IJ,Khan NA,Haque E,Jhung SH:Chemical and thermalstability of isotypic metal–organic frameworks.Chem Eur J2011,17:6437-6442.35.Shekhah O,Liu J,Fischer RA,Woll C:MOF thinﬁlms:existingand future applications.Chem Soc Rev2011,40:1081-1106. 36.Caro J:Are MOF membranes better in gas separation thanthose made of zeolites.Curr Opin Chem Eng2011,1:77-83. MOF membranes developed and tested for gas separation during the past5years have been reviewed.The structuralﬂexibility of MOFs prevents a sharp molecular sieving effect.Mixed-matrix membranes containing MOFs are predicted for the near future.37.Keskin S,Sholl DS:Efﬁcient methods for screening of metalorganic framework membranes for gas separations usingatomically detailed ngmuir2009,25:11786-11795. An efﬁcient approximate method is introduced to screen MOF mem-branes for gas separation with a connection between mixture adsorption and mixture self-diffusion properties.The method is applied to MOF membranes with chemical diversity for light gas separation.38.Bux H,Chmelik C,Krishna R,Caro J:Ethene/ethane separationby ZIF-8membrane:molecular correlation of permeation,adsorption,diffusion.J Membr Sci2011,369:284-289.39.Vinh-Thang H,Kaliaguine S:MOF-based mixed-matrix-membranes for industrial applications.In CoordinationPolymers and Metal Organic Frameworks.Edited by Ortiz OL,Ramı´rez LD.Nova Science Publishers;2011.40.Keskin S,Sholl DS:Selecting metal organic frameworks asenabling materials in mixed matrix membranes for highefﬁciency natural gas puriﬁcation.Energy Environ Sci2010,3:343-351.41.Chen YF,Hu ZQ,Gupta KM,Jiang JW:Ionic liquid/metal–organicframework composite for CO2capture:a computationalinvestigation.J Phys Chem C2011,115:21736-21742.42.Tan JC,Cheetham AK:Mechanical properties of hybridinorganic-organic framework materials:establishingfundamental structure–property relationships.Chem Soc Rev 2011,40:1059-1080.43.Cychosz KA,Ahmad R,Matzger AJ:Liquid phase separation by crystalline microporous coordination polymers.Chem Sci2010,1:293-302.This perspective details the experimental studies reported on liquid-phase separation using microporous coordination polymers(MCPs).Guest mole-cules examined include those as small as water to large organic dyes.In many cases,MCPs outperform zeolites and activated carbons in both kinetics and efﬁciency.Recent development of in silico molecular modeling Jiang143。

The Detection of Crystalline Silicates in Ultra-Luminous Infrared Galaxies

Features indicate presence of mineral forsterite (Mg2SiO4)
Previously, crystalline silicates have only been observed in circumstellar environments
Infer fraction of crystalline silicates in sample from peak optical depths of 10 µm amorphous and 16 µm crystalline bands
Crystalline-to-amorphous ratio in 12 ULIRGs is 7-15 times larger than upper limit for that in ISM of Milky Way
Timescale for injection of crystalline silicates into ISM is short in merger-driven starburst environment Timescale for amorphization of crystalline silicates ~ 108 yr
Close inspection
Weak and narrow absorption features near 16, 19, and 23 µm
Emission and absorption features at wavelengths
Also featured in Galactic sources with strong silicate features
Attributed to presence of cຫໍສະໝຸດ ystalline silicates

磷化铟晶体半导体材料的研究综述

文献综述课题名称磷化铟晶体半导体材料的研究学生学院机电工程学院专业班级2013级机电（3）班学号135学生姓名王琮指导教师路家斌2017年01月06日中文摘要磷化铟(InP)已成为光电器件和微电子器件不可或缺的重要半导体材料。

本文详细研究了快速大容量合成高纯及各种熔体配比条件的InP材料；大直径 lnP 单晶生长；与熔体配比相关的缺陷性质；lnP中的VIn心相关的缺陷性质和有关InP材料的应用，本文回顾了磷化铟( InP)晶体材料的发展过程,介绍了磷化铟材料的多种用途和优越特性，深入分析InP合成的物理化学过程，国际上首次采用双管合成技术，通过对热场和其他工艺参数的优化，实现在60—90分钟内合成4．6Kg 高纯InP多晶。

通过对配比量的调节，实现了熔体的富铟、近化学配比，富磷等状态，为进一步开展不同熔体配比对InP性质的影响奠定了基础.关键词：磷化铟磷注入合成晶体材料器件ABSTRACTIndium Phosphide (InP) has been indispensable to both optical and electronic devices．This paper used a direct P—injection synthesis and LEC crystal growth method to prepare high purity and various melt stoichiometry conditions polycrystalline InP and to grow high quality,large diameter InP single crystal in our homemade pullers．In this work，we have obtained the abstract this paper looks back the developing process on the bulk InP crystals, introduces vario us uses a nd superior character of the InP ma terials and a large quantity of high purity InP crystal materialhas been produced by the phosphorus in-situ injection synthesis and liquid encapsulated Czochralski(LEC) growth process．In the injection method，phosphorus reacts with indium very quickly so that the rapid polycrystalline synthesis is possible．The quartz injector with two Or multi-transfer tubes was used to improve the synthesis result．It will avoid quartz injector blast when the melt was indraft into the transfer tube．The injection speed，melt temperature，phosphorus excess，and SO on are also important for a successful synthesis process．About 4000—60009 stoichiometric high purity poly InP is synthesized reproducibly by improved P-injection method in the high—pressure puller．Keywords：InP , P-injection synthesis, Crystal , Material, Device引言磷化铟( InP) 是重要的Ⅲ-Ⅴ族化合物半导体材料之一,是继Si、Ga As之后的新一代电子功能材料。

溶液空间限域法制备有机-无机杂化卤化铅钙钛矿单晶薄膜及其器件应用研究进展

第53卷第4期2024年4月人㊀工㊀晶㊀体㊀学㊀报JOURNAL OF SYNTHETIC CRYSTALS Vol.53㊀No.4April,2024溶液空间限域法制备有机-无机杂化卤化铅钙钛矿单晶薄膜及其器件应用研究进展张庆文,单东明,张㊀虎,丁㊀然(吉林大学电子科学与工程学院,集成光电子学国家重点实验室,长春㊀130012)摘要:近年来,有机-无机杂化卤化铅钙钛矿材料因其出色的光电特性在国际上备受瞩目,并已成功应用于太阳能光伏㊁光电探测㊁电致发光等多个领域㊂目前绝大部分器件研究都集中在钙钛矿多晶材料上,但钙钛矿单晶材料拥有更低的缺陷态密度㊁更高的载流子迁移率㊁更长的载流子复合寿命㊁更宽的光吸收范围,以及更高的稳定性等优异的性质,可有效减少载流子传输过程中的散射损失,以及在晶界处的非辐射复合,并抑制离子迁移所引起的迟滞效应㊂采用钙钛矿单晶薄膜作为器件有源层有望制备性能更高效且更稳定的钙钛矿光电器件㊂目前,已报道的多种钙钛矿单晶薄膜制备方法包括溶液空间限域法㊁化学气相沉积法㊁自上而下加工法等,其中溶液空间限域法的发展和应用最为广泛㊂本文聚焦利用溶液空间限域法制备高质量钙钛矿单晶薄膜的相关方法,以及钙钛矿单晶薄膜在光电探测器㊁太阳能电池㊁场效应晶体管和发光二极管等相关器件应用中的研究进展,并对钙钛矿单晶薄膜及其光电器件的未来发展趋势进行了展望㊂关键词:钙钛矿半导体材料;溶液空间限域法;钙钛矿单晶薄膜;光电子器件;单晶薄膜生长中图分类号:O78;O484;TN36㊀㊀文献标志码:A ㊀㊀文章编号:1000-985X (2024)04-0572-13Research Progress on Preparation of Organic-Inorganic Hybrid Lead Halide Perovskite Single-Crystalline Thin-Films by Solution-Processed Space-Confined Method and Their Device ApplicationsZHANG Qingwen ,SHAN Dongming ,ZHANG Hu ,DING Ran(State Key Laboratory of Integrated Optoelectronics,College of Electronic Science and Engineering,Jilin University,Changchun 130012,China)㊀㊀收稿日期:2023-11-20㊀㊀基金项目:国家重点研发计划青年科学家项目(2022YFB3607500);国家自然科学基金(62274076)㊀㊀作者简介:张庆文(1999 ),男,山东省人,硕士研究生㊂E-mail:zhangqw1012@ ㊀㊀通信作者:丁㊀然,教授,博士生导师㊂E-mail:dingran@Abstract :In recent years,organic-inorganic hybrid lead halide perovskite materials have attracted much attention in the world because of their excellent photoelectric properties,and have been successfully applied in many fields such as solar photovoltaic,photoelectric detection,electroluminescence and so on.At present,most of the device research focuses on perovskite polycrystalline materials,but perovskite single crystal materials have excellent properties such as lower defect state density,higher carrier mobility,longer carrier recombination lifetime,wider light absorption range and higher stability,which can effectively reduce the scattering loss during carrier transport and non-radiative recombination at the grain boundary,and inhibit the hysteresis effect caused by ion ing perovskite single crystal thin film as the active layer of the device is expected to produce more efficient and stable perovskite photoelectric devices.At present,many preparation methods of perovskite single crystal films have been reported,mainly including solution-processed space-confined method,chemical vapor deposition method,top-down processing method,etc.Among them,solution-processed space-confined method is the most widely developed and applied.This paper focuses on the preparation of high-quality perovskite single crystal thin films by solution-processed space-confined method,and the research progress of perovskite single crystal thin films in photodetectors,solar cells,field effect transistors,light-emitting diodes and other related devices,and prospects the future development trend of perovskite single crystal thin films and photoelectric devices.㊀第4期张庆文等:溶液空间限域法制备有机-无机杂化卤化铅钙钛矿单晶薄膜及其器件应用研究进展573㊀Key words:hybrid perovskite semiconductor;solution-processed space-confined method;perovskite single-crystalline thin-film;optoelectronic device;growth of single crystal thin film0㊀引㊀㊀言近年来,有机-无机杂化卤化铅钙钛矿材料因高的光吸收系数[1]㊁高的载流子迁移率[2-3]㊁长的载流子扩散距离[4]㊁带隙可调谐[5-7]等优异的光电性能,引起了科研界和产业界的广泛关注㊂尤其是在光伏器件领域,钙钛矿电池的功率转换效率(power conversion efficiency,PCE)从最初的3.8%[8]攀升到目前的25.9%[9],发展速度出人意料且远超其他光伏材料体系㊂理论计算得到单结钙钛矿电池的最高转换效率可达33%,这一效率优于晶体硅的理论极限效率29.4%㊂除光伏领域外,钙钛矿材料在光电探测[5,10-15]㊁电致发光[16-19]㊁光泵激光[20-23]和辐射探测[24-26]等诸多光电领域也展现出巨大的应用前景㊂有机-无机杂化卤化铅钙钛矿材料化学结构式通常为ABX3,一般为立方体或八面体结构[27],对于典型的三维钙钛矿材料,其中A代表一价阳离子(如MA+㊁FA+等),B代表二价Pb2+阳离子,X为一价卤素阴离子(如Cl-㊁Br-㊁I-等)㊂在钙钛矿材料中,B离子位于立方晶胞的中心[28],被6个X离子包围形成配位立方八面体结构㊂钙钛矿光电器件有源层材料以多晶薄膜为主,多晶材料虽然在器件应用方面已展现出卓越的性能,但是内部存在大量晶界,且在晶界处存在高密度的晶格位错,以及无序的晶粒生长,从而导致薄膜内存在大量的晶格缺陷和可自由移动的离子㊂多晶膜内大量晶粒㊁晶界㊁空隙和表面缺陷等,会显著增大非辐射复合过程并诱使激子猝灭,严重限制光电及电光转换效率[29-30]㊂同时,在外场作用下钙钛矿多晶膜中会产生明显的离子迁移现象,移动的离子会抑制自由载流子的感生㊁积累与传输,也将极大影响器件的光电性能[31]㊂相比之下,钙钛矿单晶拥有更低的缺陷态密度㊁更长的载流子扩散长度㊁更长的载流子复合寿命㊁更宽的光吸收范围,以及更高的稳定性等[32-33]㊂这些优秀的本征特性为克服以上挑战提供了良好的载体,有望制备性能更高效且更稳定的钙钛矿光电器件㊂从晶体形态学角度区分,钙钛矿单晶材料主要可分为块体[34-35]和薄膜两种类型[36-38]㊂相比于单晶块体材料,单晶薄膜更易于与传统半导体工艺相集成,并有望制备性能更加优越的光电器件,更因其突出的柔性[39]和机械性,在未来柔性电子器件领域也展现出良好的应用前景㊂目前,已报道的钙钛矿单晶薄膜制备方法中,主要包括溶液空间限域法[36-37,40]㊁化学气相沉积法[41-44]㊁自上而下加工法[13,45-48]等,其中溶液空间限域法的发展和应用最为广泛㊂由于单晶各向异性生长,为了有效控制单晶薄膜厚度,抑制薄膜沿垂直纵向方向生长,并且提高水平横向方向的生长速率㊁增大薄膜的表面积,常引入空间结构限制策略,实现可控制备钙钛矿单晶薄膜㊂本文聚焦利用溶液空间限域法制备高质量钙钛矿单晶薄膜的相关技术方法,以及钙钛矿单晶薄膜在光电探测器㊁太阳能电池㊁场效应晶体管和电致发光器件等相关器件应用中的研究进展㊂同时,对未来钙钛矿单晶薄膜材料的发展及其应用所面临的难题提出可行的解决方案㊂1㊀钙钛矿单晶薄膜生长策略目前,溶液法生长钙钛矿单晶块体技术较为成熟,包括冷却结晶法[4,49-52]㊁逆温结晶法[46,53-57]㊁反溶剂扩散法[58-62]等方法,但单晶块体的厚度较厚,展现出较高的光吸收损耗和较长的激子扩散距离,不适于垂直结构型光电器件的应用㊂为了进一步扩展钙钛矿单晶材料在光电器件领域的应用,急需开发厚度和形貌可控㊁重复性高的钙钛矿单晶薄膜制备方法㊂2016年,陕西师范大学刘生忠教授团队报道采用空间限域结合动态流反应系统的生长方法,通过控制两个玻璃片之间的间隙大小,确保钙钛矿单晶薄膜在预设的限域空间结构内生长,达到单晶薄膜厚度可控的目的,如图1(a)所示[37]㊂利用蠕动泵驱动空隙中溶液流动,为单晶薄膜生长提供源源不断的前驱体溶液,最终实现一系列厚度约为150μm的MAPbI3单晶薄片㊂然而,微米厚度的钙钛矿单晶薄膜依然无法满足垂直结构型器件的需求,通过施加外部压力的方式来控制几何限域空间的间隙距离,达到进一步减薄钙钛矿单晶薄膜的作用㊂2016年,中国科学院化学研究所胡劲松研究员团队设计如图1(b)所示装置,实现可控制备厚度均匀的钙钛矿单晶薄膜生长方法[36]㊂实验具体流程是将两个平面衬底夹在一起,通过控制夹具的压力来限制几何限域空间间隙,再垂直浸入钙钛矿前驱体溶液中,在毛细力的作用下溶液会填充满整个限域空间,然后加热底部前驱体溶液,控制溶剂挥发速率,形成底部饱和㊁顶部过574㊀综合评述人工晶体学报㊀㊀㊀㊀㊀㊀第53卷饱和的溶液环境,由于温度差引起的热对流,底部的溶液不断向顶部流动补充,为限域空间内生长钙钛矿单晶薄膜提供充足的前驱体溶液㊂制备的单晶薄膜具有厚度从纳米至微米可调㊁表面积达到亚毫米尺寸㊁横纵比可达~105等特点㊂同时,该方法可将钙钛矿单晶薄膜制备在各种衬底(如玻璃㊁石英㊁氧化铟锡(indiumtin oxide,ITO)㊁氟掺杂氧化锡(F-doped tin oxide,FTO))上,其厚度只取决于两个衬底之间的间隙距离,不同厚度的薄膜呈现出多彩均匀的颜色㊂图1㊀溶液空间限域法中厚度可控策略制备钙钛矿单晶薄膜㊂(a)溶液空间限域结合动态流反应系统生长法[37];(b)溶液空间限域法生长厚度可调的钙钛矿单晶薄膜[36]Fig.1㊀Strategies for the growth of thickness-controlled perovskite single-crystalline thin-films.(a)Schematic diagram of the geometry-confined dynamic-flow reaction system[37];(b)schematic diagram of the solution-processed space-confined growthmethod for perovskite single-crystalline thin-films[36]为了扩大钙钛矿单晶薄膜的横向尺寸,从晶体成核动力学角度出发,降低溶液空间限域法中衬底的表面能,将有助于提高溶剂中离子的扩散速度和扩散距离,诱导晶体沿横向方向加速生长㊂2017年,美国北卡罗来纳大学教堂山分校黄劲松教授团队提出对衬底表面进行疏水处理,在ITO衬底表面旋涂疏水的聚[双(4-苯基)(2,4,6-三甲基苯基)胺](Poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine,PTAA)空穴传输层材料,再用两片PTAA修饰后的ITO衬底构建限域空间,在空间内滴加MAPbBr3前驱体溶液后,将衬底结构置于㊀第4期张庆文等:溶液空间限域法制备有机-无机杂化卤化铅钙钛矿单晶薄膜及其器件应用研究进展575㊀110ħ热台上[1]㊂对比PTAA处理和未处理的衬底所构建限域空间内前驱体溶液的扩散差异,从图2(a)不难发现,由于疏水材料处理的衬底表面具有较低的表面能,将加速前驱体溶液中离子的扩散速率,解决生长过程中离子长程输运差的问题,有助于减少多晶成核结晶概率,同时增大单晶薄膜的横向生长尺寸㊂基于该衬底修饰方法,实现MAPbBr3单晶薄膜厚度可控制在10~20μm,横向截面尺寸可达数十mm2,该工作证明了对衬底表面进行合理改性对于控制钙钛矿单晶薄膜横向生长至关重要㊂2020年,北京大学马仁敏教授团队采取对衬底表面进行特异性处理的策略[63]㊂具体方式是对玻璃衬底进行不同的亲疏水处理,由于具有特异性的亲疏水能力,衬底展现出大小不同的溶液接触角㊂在观测亲疏水能力与单晶成核密度之间的关系后,发现从亲水到疏水的转变过程中,衬底表面的成核密度显著降低㊂分析其原因是亲水表面的成核自由能垒相对低于疏水条件下的表面成核自由能垒,从而拥有较快速的成核速率;并且亲水表面更易于吸附和捕获前驱体溶液中的离子,而降低了离子的扩散速率,导致单晶结晶速率较为缓慢㊂因此,疏水处理的衬底可有效降低单晶成核密度,并且加快单晶生长速率,更易于制备大尺寸的钙钛矿单晶薄膜㊂制得的MAPbBr3单晶薄膜边长尺寸达到1cm,厚度控制在10μm,同时展现出较好的结晶质量,薄膜陷阱态密度仅为1011cm-3,载流子迁移率超过60cm2/(V㊃s)㊂除了衬底修饰策略,衬底自身独特的表面特征也有助于钙钛矿单晶薄膜的生长㊂2020年,天津理工大学吴以成教授团队以云母作为溶液空间限域法的生长衬底[64],如图2(b)所示,将含有适量油酸(oleic acid,OA)的钙钛矿前驱体溶液滴加到两片云母组成的间隙中,旋转云母衬底去除多余的前驱体溶液,然后放置于热板上加热,最终获得超薄的MAPbBr3单晶薄膜㊂该方法是基于云母表面的钾原子与钙钛矿中卤素原子之间会产生较强的相互作用,导致界面能降低并促进钙钛矿单晶薄膜在云母表面横向生长,同时油酸作为表面改性剂附着在钙钛矿表面,抑制钙钛矿单晶薄膜沿纵向方向的生长,最终成功制备出厚度仅为8nm㊁横向尺寸可达数百微米的MAPbBr3单晶薄膜㊂图2㊀溶液空间限域法中衬底修饰策略制备钙钛矿单晶薄膜㊂(a)PTAA处理和未处理的ITO衬底结构中前驱体溶液扩散速度对比图[1];(b)云母衬底上生长钙钛矿单晶薄膜流程示意图[64]Fig.2㊀Substrate modification for the growth of perovskite single-crystalline thin-films.(a)Comparison of the diffusion rate of precursor solution within the PTAA treated and untreated ITO substrates[1];(b)growth of perovskite single-crystalline thin-films on mica substrates[64]钙钛矿单晶薄膜的生长开始于成核阶段,考虑到处于复杂溶液环境中,晶体将发生各向异性生长,容易形成多个晶核,并诱使出现晶畴㊁晶界等结构,严重影响钙钛矿单晶成膜的结晶质量[65]㊂为解决这一问题,科研人员提出了一种晶种法技术策略,首先生长钙钛矿单晶种子,再将种子转移到目标衬底,最后在合适的溶液环境中再结晶生长形成高质量的钙钛矿单晶薄膜㊂2018年,中国科学院化学研究所宋延林研究员团队提出了一种溶液空间限域结合晶种印刷法的生长策略,通过晶种再生长的方式,实现了厚度可控㊁重复性好㊁576㊀综合评述人工晶体学报㊀㊀㊀㊀㊀㊀第53卷结晶质量高的钙钛矿单晶薄膜[66]㊂如图3(a)所示,首先使用喷墨打印技术将钙钛矿前驱体溶液选择性滴加在目标衬底上,随着前驱体溶液的挥发,形成规则排布的钙钛矿单晶种子㊂获得的钙钛矿单晶种子将有效抑制无序成核结晶现象㊂然后,将载有钙钛矿单晶种子的衬底转移并浸入到钙钛矿前驱体饱和溶液中,置于热台上加热结晶后,通过控制钙钛矿单晶种子的数量和尺寸,最终制备出批量的毫米级钙钛矿单晶薄膜㊂2021年,韩国首尔大学Lee教授团队进一步拓展了晶种生长法,结合种子转移技术,如图3(b)所示[67]㊂首先在两片玻璃片中注入前驱体溶液,玻璃片之间由厚度为25μm的聚四氟乙烯(polytetrafluoroethylene,PTFE)薄膜隔开,在110ħ的加热温度下,过饱和的钙钛矿前驱体溶液成核结晶,形成厚度为23μm㊁尺寸为100~200μm 的MAPbBr3单晶种子㊂然后,挑选出单个种子转移至一个密封式液体池腔体中,随着浓度为1mol/L的MAPbBr3前驱体溶剂以5μL/min速率源源不断地流入液体池腔体内,基于逆温结晶法,MAPbBr3单晶薄膜将匀速生长,最终制得了高质量㊁大尺寸的MAPbBr3单晶薄膜,其厚度为40μm,表面积可达16.23mm2,表面粗糙度为0.51nm,缺陷态密度仅有7.61ˑ108cm-3㊂图3㊀溶液空间限域法中晶种法策略制备钙钛矿单晶薄膜㊂(a)溶液空间限域结合晶种印刷法制备钙钛矿单晶薄膜技术流程示意图[66];(b)晶种生长法结合晶种转移技术制备钙钛矿单晶薄膜技术流程示意图[67]Fig.3㊀Seed-induced methods for the growth of perovskite single-crystalline thin-films.(a)Technical flow diagram of preparation of perovskite single crystal film by solution-processed space-confined combined with seed printing[66];(b)process flow diagram of preparation of perovskite single crystal thin film by seed growth and seed transfer technology[67]图案化生长钙钛矿单晶薄膜对于推动钙钛矿单晶材料面向集成化光电器件应用至关重要㊂其主要思路是通过引入周期性的模板,构建结构化限域空间用于生长图案化钙钛矿单晶[68-74]㊂2021年,合肥工业大学罗林保教授团队利用高密度数字视频光盘(digital video disc,DVD)上的沟道作为结构化限域空间用于溶液空间限域法,如图4(a)所示[71]㊂首先,将聚二甲基硅氧烷(polydimethylsiloxane,PDMS)溶液旋涂在准备好的DVD磁盘上,固化后形成与磁盘沟道结构和形貌一致的PDMS模板㊂然后,在亲水性衬底上滴加钙钛矿前驱体溶液,溶液在亲水衬底上形成一层均匀的液膜,再将表面具有周期性沟道结构的PDMS模板覆盖其上,前驱体溶液便被重新分配并限制在PDMS模板与亲水性衬底形成的纳米沟道之间㊂放置于热台上加热之后,晶体沿着纳米沟道不断生长,最终形成规则且均匀的钙钛矿单晶阵列,得到的钙钛矿单晶阵列的结构完全与磁盘沟道形貌相一致,并可实现在不同衬底上生长大规模钙钛矿单晶阵列结构㊂2022年,苏州大学揭建胜教授团队开发了类似的三维限制结晶方法,在三维结构化的微通道模板上方利用一个三角形PDMS 基板协助溶液剪切过程,用于生长钙钛矿单晶阵列,PDMS模板紧密地附着在微通道表面,避免了溶液剪切㊀第4期张庆文等:溶液空间限域法制备有机-无机杂化卤化铅钙钛矿单晶薄膜及其器件应用研究进展577㊀过程中对微通道的破坏,同时利用PDMS模板表面的疏水性,可以有效防止溶液黏附在三角形PDMS基板上,如图4(b)所示[72]㊂在底部进行加热的情况下,缓慢移动三角形玻璃基板,钙钛矿前驱体溶液逐渐挥发结晶,最终形成与模板结构相同的MAPbI3单晶阵列㊂为了进一步提高钙钛矿单晶阵列横向尺寸,韩国汉阳大学Sung教授团队引入滚筒印刷技术,如图4(c)所示[73]㊂首先,钙钛矿前驱体溶液加在180ħ加热的基板衬底上,通过旋转图案化的PDMS模具包裹的圆柱形金属滚轮,PDMS模具上具有宽度为10mm㊁深度为200nm的周期性阵列,前驱体溶液被限制在模具和基板衬底之间,随着前驱体溶液的迅速蒸发而结晶,最终制得的钙钛矿单晶薄膜阵列与滚筒图案完全一致㊂成功实现了总宽度为10mm,周期尺寸为400nm,厚度为200nm的MAPbI3单晶薄膜阵列㊂利用该方法不仅可以在横向方向上约束钙钛矿单晶的生长,并且实现滚筒印刷制备大尺度钙钛矿单晶薄膜阵列的目的㊂通过上述总结,围绕溶液空间限域法制备大尺寸㊁高质量钙钛矿单晶薄膜,详细阐述了从厚度可控㊁衬底修饰㊁晶种生长㊁图案化生长等几个主要方面的生长和制备方法,相关性能参数如表1所示,对于未来实现可控制备钙钛矿单晶薄膜材料,进一步扩展其在光电器件领域的应用至关重要㊂图4㊀溶液空间限域法中图案化生长策略制备钙钛矿单晶薄膜㊂(a)磁盘沟道模板生长钙钛矿单晶阵列的技术流程图[71];(b)三维限制结晶方法生长钙钛矿单晶阵列装置示意图[72];(c)滚筒印刷技术制备大尺度钙钛矿单晶阵列的装置流程图[73] Fig.4㊀Periodic structures for the growth of perovskite single-crystalline thin-films.(a)Digital channel template for the growth of perovskite single-crystalline arrays[71];(b)schematic diagram of apparatus for growing perovskite single crystal array by a three-dimensional restricted crystallization method[72];(c)flow chart of device for preparing large-scale perovskite singlecrystal array by roller printing technology[73]578㊀综合评述人工晶体学报㊀㊀㊀㊀㊀㊀第53卷表1㊀溶液空间限域法及其改进策略制备钙钛矿单晶薄膜的相关性能参数Table1㊀Performance parameters of the perovskite single-crystalline thin-films prepared by solution-processedspace-confined method and its improvement strategySolution-processed space-confined method and its improvement strategy Perovskitematerial type Thickness/μmDensity of defectstates/cm-3Carrier mobility/(cm2㊃V-1㊃s-1)Surface dimension ReferenceDynamic-flow reaction system MAPbI3~1506ˑ10839.6 5.84mmˑ5.62mm[37] Thickness controlledgrowth method MAPbBr30.01~1 4.8ˑ101015.7Hundreds of microns[36]Substrate treatment MAPbI310~40Electron:36.8ʃ3.7Hole:12.1ʃ1.5Tens of square millimeters[1] Substrate specific processing MAPbBr3~10 1.6ˑ1011>601cm[63] Mica substrate MAPbX30.008~0.01436.5Hundreds of microns[64] Seed printing method MAPbX3,CsPbBr30.1~10 2.6ˑ101014000μm2[66] Seed transfer technology MAPbBr3407.61ˑ10816.23mm2[67] Digital channeltemplate method MAPbI3~0.065cycle:760nm[71] Three-dimensional confinedcrystallization method MAPbI30.5~58.5ˑ1010cycle:8μm[72] Rolling mould printingtechnology MAPbI30.2or0.545.64cycle:400nm[73] 2㊀钙钛矿单晶薄膜器件应用钙钛矿单晶薄膜因其高的光吸收系数㊁高的载流子迁移率㊁长的载流子扩散长度㊁带隙可调谐等优异的光电性能,被广泛应用于光电探测器㊁太阳能电池㊁场效应晶体管㊁发光二极管等器件中㊂光电探测器是基于传统光电效应将光信号转变为电信号的器件装置,其在光通信㊁激光雷达㊁医疗诊断㊁安防监控等多个领域应用广泛㊂传统光电探测器多以无机半导体材料为主,例如Si㊁GaAs㊁GaN等材料[11]㊂近年来,随着有机-无机杂化卤化物钙钛矿半导体材料的出现,其展现出的巨大的应用潜力,有望促进光电探测器在成本和性能上取得进一步的提升和跨越㊂大量研究表明,由于较低的光吸收损耗和理想的激子扩散距离,钙钛矿单晶薄膜光电探测器[68-69,75-77]相比于单晶块体探测器,在光电探测方面已展露出明显的性能优势㊂2015年,阿卜杜拉国王科学大学Bakr教授团队首次报道利用直接生长在ITO玻璃衬底上的MAPbCl3单晶薄膜,制备一种具有金属-半导体-金属器件结构的光电导型探测器[54],并展现出出色的光电探测性能,具有较高的探测率与开关比,响应时间在ms数量级,这与当时商用的III-V族半导体光电晶体管的性能几乎相当㊂2017年,黄劲松团队利用MAPbBr3单晶薄膜制作了垂直器件结构为p-i-n型的Cu/BCP/C60/MAPbBr3/PTAA/ITO钙钛矿单晶探测器[78],如图5(a)所示,该光电探测器的探测率(D∗)高达1.5ˑ1013Jones㊂由于单晶薄膜较低的缺陷态密度,探测器对于弱光探测极为敏感,探测最低可达pW/cm2量级,同时线性动态范围高达256dB,是当时报道最高的结果㊂2018年,马仁敏教授团队系统性研究了光电探测器性能与单晶薄膜厚度之间的依赖关系[14]㊂发现随着钙钛矿单晶薄膜的厚度从10μm降低到几百nm,光电探测器的探测能力提升了2个数量级,增益提升了4个数量级㊂通过优化钙钛矿单晶薄膜的厚度以及结晶度,器件的增益可达5ˑ107,增益带宽积为70GHz㊂钙钛矿材料具有可低温㊁液相制备的特点,并可与多种柔性衬底相兼容,制备可弯折的柔性光电子器件㊂同时,钙钛矿单晶薄膜展现出较好的柔性和机械性,可用于制备柔性钙钛矿单晶薄膜光电探测器㊂为此, 2020年,马仁敏教授团队引入超薄钙钛矿单晶薄膜作为有源层,制备了高性能的柔性光电探测器[39],如图5 (b)所示,该光电探测器的单晶薄膜厚度仅为20nm,器件响应度高达5600A/W,在经过1000次循环弯折后,探测器的光电流和开关比没有出现明显的下降,展现出较好的弯折稳定性㊂高质量的钙钛矿单晶纳米线阵列有利于限制载流子在几何通道内输运,提高载流子的迁移率和扩散距离㊂2021年罗林保教授团队制备的基于MAPbI3单晶纳米线阵列的光电探测器[71],在520nm入射光照射下,随入射光功率的升高,该光电探㊀第4期张庆文等:溶液空间限域法制备有机-无机杂化卤化铅钙钛矿单晶薄膜及其器件应用研究进展579㊀测器的光电流呈线性递增,最低暗电流为0.3nA,最高光电流达350nA,总开关比高达1.2ˑ103㊂同时,该探测器的响应度为20.56A/W,探测率达到4.73ˑ1012Jones㊂由于钙钛矿单晶纳米线阵列展现出良好的偏振敏感性,该类型器件也适用于探测线偏光的偏振度㊂为了解决钙钛矿材料中铅毒性[79]和不稳定性的问题,2020年,中山大学匡代彬教授团队在ITO玻璃上原位生长不含铅元素的全无机Cs3Bi2I9单晶薄膜并制备了相应的光电探测器[80]㊂制得的Cs3Bi2I9钙钛矿单晶薄膜的陷阱态密度比多晶材料低3个数量级,载流子迁移率也高出3.8ˑ104倍㊂这些优异的性质有利于实现高性能的光电探测器,基于此材料制备的垂直结构型光电探测器的开关比高达11000㊂而且,在未封装的情况下,处在潮湿环境中1000h之后,该钙钛矿单晶薄膜光探测器的光电流仍维持初始值的91%,体现了该材料出色的环境稳定性㊂由于钙钛矿多晶薄膜内存在大量的晶界㊁空穴和缺陷态等,太阳能电池存在显著的非辐射复合能量损失,限制了钙钛矿太阳能电池PCE的进一步提升㊂而无晶界㊁低缺陷态密度的钙钛矿单晶薄膜成为解决材料内在问题及器件PCE的理想材料体系㊂2017年,中国科学院深圳先进技术研究院李江宇教授团队在FTO/TiO2衬底上直接生长MAPbI3单晶薄膜,并制造了相应的钙钛矿单晶薄膜太阳能电池,该电池器件的PCE达到了8.78%[81]㊂同年,黄劲松教授团队利用在PTAA空穴传输层上直接生长的MAPbI3单晶薄膜,构建器件结构为ITO/PTAA/MAPbI3/PCBM/C60/BCP/Cu的太阳能电池器件,如图5(c)所示[1]㊂通过优化钙钛矿单晶薄膜厚度,其电池的光谱响应范围可以扩展到820nm,比相对应的多晶薄膜材料的光谱响应要宽20nm,器件的最佳短路电流密度J sc为20.5mA/cm2,开路电压V oc为1.06V,填充因子(fill factor,FF)为74.1%,PCE可达16.1%㊂在使用MAI离子溶液对单晶薄膜表面进行钝化处理之后,有效降低了MAPbI3单晶薄膜表面的电荷陷阱,器件最佳PCE提升到17.8%㊂2019年,Bakr教授团队利用20μm厚的MAPbI3单晶薄膜制备太阳能电池,器件结构为ITO/PTAA/MAPbI3/C60/BCP/Cu[82]㊂该钙钛矿单晶薄膜电池器件的PCE达到21.09%,填充因子FF为84.3%㊂之后,该团队通过优化前驱体溶液,采用碳酸丙烯酯(propylene carbonate,PC)和γ-丁内酯(1,4-butyrolactone,GBL)的混合溶剂,90ħ下生长MAPbI3钙钛矿单晶薄膜㊂基于此单晶材料制备的钙钛矿太阳能电池的V oc明显提高,PCE达到21.9%[84]㊂2021年,该团队在之前的器件结构基础上,将钙钛矿单晶的成分改为混合阳离子FA0.6MA0.4PbI3钙钛矿单晶,如图5(d)所示,制备的钙钛矿太阳能电池对近红外响应要比纯FAPbI3器件扩展了50meV,J sc达到26mA/cm2,PCE达到22.8%[84]㊂2023年,该团队在亲水性的([2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid,MeO-2PACz)单分子层表面生长FA0.6MA0.4PbI3钙钛矿单晶薄膜,与PTAA上生长的单晶薄膜相比,MeO-2PACz有效提高了钙钛矿单晶薄膜与衬底的机械粘附力,PCE达到创纪录的23.1%[85]㊂伴随着钙钛矿单晶薄膜生长技术的更新和迭代,钙钛矿单晶薄膜太阳能电池的器件性能有望超越钙钛矿多晶太阳能电池,在太阳能电池器件领域占据一席之地[86]㊂从钙钛矿材料结构角度出发,由金属阳离子和卤化物阴离子形成的强共价或离子键相互作用结合的钙钛矿八面体骨架结构,将为材料提供高的载流子迁移率骨架模型,据理论预测的迁移率最高可达1000cm2/(V㊃s);有机阳离子可以间接扭曲无机骨架,在分子尺度上影响材料的晶体结构和电学特性㊂因此,钙钛矿材料因其展现出较高的载流子迁移率,被认为是发展新一代半导体电子技术最理想的光电材料㊂基于钙钛矿单晶薄膜材料的场效应晶体管研究起步相对较晚,2018年,阿卜杜拉国王科技大学Amassian教授团队制备了底栅顶接触的钙钛矿单晶薄膜场效应晶体管器件,器件的沟道长度为10~150μm,如图5(e)所示[87]㊂该团队设计和制备了一系列基于MAPbCl3㊁MAPbBr3㊁MAPbI3单晶薄膜的场效应晶体管器件,测量和分析器件的转移和传输特性曲线,其空穴迁移率最高分别可达2.6㊁3.1㊁2.9cm2/(V㊃s),电子迁移率分别为2.2㊁1.8㊁1.1cm2/(V㊃s),且器件开关比分别可达2.4ˑ104㊁4.8ˑ103㊁6.7ˑ103㊂该系列场效应晶体管器件展现出良好的电学输运特性,为进一步推动钙钛矿单晶薄膜材料在集成电子器件领域的应用提供了良好的研究基础㊂钙钛矿发光二极管(perovskitelight emitting diodes,PeLED)近年来也发展迅速,自2014年英国剑桥大学的Friend教授课题组首次报道室温下PeLED器件以来,PeLED以其优异的光电性能㊁较低的器件成本,以及。

多晶硅薄膜的两步激光晶化技术_曾祥斌

收稿日期:2001-09-13基金项目:香港科技大学电气与电子工程系资助项目(HPKUST 6183100E )作者简介:曾祥斌(1962-),男,湖北天门市人,副教授,博士,主要从事半导体物理与器件、薄膜器件和有源矩阵液晶显示器等方面的研究工作。

文章编号:1004-2474(2002)04-0315-03多晶硅薄膜的两步激光晶化技术曾祥斌,徐重阳,王长安(华中科技大学　电子科学与技术系,武汉430074) 摘　要:采用两步激光晶化技术获得了多晶硅薄膜,分析计算了激光晶化时薄膜中的温度分布及表面温度与激光功率密度的关系,利用计算结果确定并优化了激光晶化时的工艺参数,采用该技术制备了性能优良的顶栅多晶硅薄膜晶体管,测量了薄膜晶体管的转移特性与输入输出特性,从多晶硅薄膜的制备工艺上分析了提高薄膜晶体管性能的原因。

关键词:激光晶化;多晶硅薄膜;薄膜晶体管中图分类号:T N 304.55 文献标识码:AThe Study of Two -Step Laser Crystallization Techniqueof Polycrystalline Silicon Thin FilmZENG Xiang -bin ,XU Zhong -yang ,WANG Chang -an(Dep t.of Electronic Science an d T echnology ,Hu azh ong U nivers ity of S cience and T ech nology,W uhan 430074,Ch ina) Abstract :T he po ly -Si thin film w as prepar ed using a nov el tw o-st ep laser cry st allization technique.T he t em-per atur e distr ibutio n and sur face temper ature of po ly-Si thin film during laser cry stallizat ion was ca lculat ed by so lv -ing the thermal-t ransfer conduction equatio n.T he pr ocess para meters of laser cry st allization o f po ly -Si thin film w ere considered and o pt imized using the calcula ted r esults .T he high -per for mance po ly -Si T F T s wer e achiev ed us-ing two -step laser cr ystallizatio n technique.T he I -V and tr ansfer char acterist ics of po ly -Si T F T s fabr icated using tw o-st ep laser cr ystalliza tio n and co nventio nal sing le -step laser cr ysta llizatio n wer e measured.T he reaso n that the character istics of po ly -Si T FT wer e impr ov ed by t wo -step laser cry st allization wa s analyzed .Key words :laser cry st allization ;poly -Si thin film ;thin film tr ansist or s1　引言激光晶化方法是诸多获得多晶硅薄膜的最佳方法之一[1],晶化效果与起始a -Si 薄膜的参数密切有关[2]。

高迁移率聚合物半导体材料

段是研发了以聚噻吩和聚亚苯基乙烯为显著代表的材料，这些材料体的稳定性。双极传输型聚合物制作半导体的互补边路和场效应晶
具有可溶液特征，能够加工制作聚合物半导体。第三个阶段是研发体管的过程也日趋简单化、便捷化，制作的成本造价也非常低。但是
了给体－受体半导体材料［２］。目前常用的高迁移率聚合物半导体材双极型聚合物的电荷传输能级要求非常严格，其需要势垒最好保持
科技论坛
·８５·
高迁移率聚合物半导体材料
李小锋
（杭州士兰集成电路有限公司，浙江杭州３１００１８）
摘要：半导体材料作为场效应晶体管的关键组成元素，严重的影响器件性能，相对于小分子半导体材料，聚合物半导体材料具有很多优势，比如便于溶液加工、适用于室温制备等。目前，高迁移率聚合物半导体材料经过多年研发，已经取得了突飞猛进的成果，并且经过不断的创新，诞生了各种结构新颖、性能良好的聚合物半导体材料，不断优化器件制备工艺，使得聚合物场效应晶体管的载流子迁移率从１０－５ｃｍ２ｖｓ－１－１提升到了３６．３ｃｍ２ｖ－１ｓ－１。详细地描述了高迁移率聚合物半导体材料的研究现状，分析了高迁移率聚合物在半导体器件设计中的应用情况，从空穴传输型、电子传输型和双极传输型等三个方面分析高迁移率聚合物半导体研发现状，归纳和总结半导体材料，从而可以进一步的为半导体器件构筑提供一定的指导。
也引起了许多产业公司和科研院校的研究兴趣［１］。目前，通过调查和成在一起可以形成一个互补电路，又被称为双极传输型聚合物半导
分析，发现聚合物半导体研究制造和普及使用经历了三个非常关键体材料。与传统的材料共混方法、层状复合方法相比，直接构建和合
的阶段，第一个阶段是提出以聚乙炔为显著代表的材料；第二个阶成一个双极型半导体材料，可以有效地降低自身的功耗，提高半导

毕业设计论文塑料注射成型

Modeling of morphology evolution in the injection moldingprocess of thermoplastic polymersR.Pantani,I.Coccorullo,V.Speranza,G.Titomanlio* Department of Chemical and Food Engineering,University of Salerno,via Ponte don Melillo,I-84084Fisciano(Salerno),Italy Received13May2005;received in revised form30August2005;accepted12September2005AbstractA thorough analysis of the effect of operative conditions of injection molding process on the morphology distribution inside the obtained moldings is performed,with particular reference to semi-crystalline polymers.The paper is divided into two parts:in the ﬁrst part,the state of the art on the subject is outlined and discussed;in the second part,an example of the characterization required for a satisfactorily understanding and description of the phenomena is presented,starting from material characterization,passing through the monitoring of the process cycle and arriving to a deep analysis of morphology distribution inside the moldings.In particular,fully characterized injection molding tests are presented using an isotactic polypropylene,previously carefully characterized as far as most of properties of interest.The effects of both injectionﬂow rate and mold temperature are analyzed.The resulting moldings morphology(in terms of distribution of crystallinity degree,molecular orientation and crystals structure and dimensions)are analyzed by adopting different experimental techniques(optical,electronic and atomic force microscopy,IR and WAXS analysis).Final morphological characteristics of the samples are compared with the predictions of a simulation code developed at University of Salerno for the simulation of the injection molding process.q2005Elsevier Ltd.All rights reserved.Keywords:Injection molding;Crystallization kinetics;Morphology;Modeling;Isotactic polypropyleneContents1.Introduction (1186)1.1.Morphology distribution in injection molded iPP parts:state of the art (1189)1.1.1.Modeling of the injection molding process (1190)1.1.2.Modeling of the crystallization kinetics (1190)1.1.3.Modeling of the morphology evolution (1191)1.1.4.Modeling of the effect of crystallinity on rheology (1192)1.1.5.Modeling of the molecular orientation (1193)1.1.6.Modeling of theﬂow-induced crystallization (1195)ments on the state of the art (1197)2.Material and characterization (1198)2.1.PVT description (1198)*Corresponding author.Tel.:C39089964152;fax:C39089964057.E-mail address:gtitomanlio@unisa.it(G.Titomanlio).2.2.Quiescent crystallization kinetics (1198)2.3.Viscosity (1199)2.4.Viscoelastic behavior (1200)3.Injection molding tests and analysis of the moldings (1200)3.1.Injection molding tests and sample preparation (1200)3.2.Microscopy (1202)3.2.1.Optical microscopy (1202)3.2.2.SEM and AFM analysis (1202)3.3.Distribution of crystallinity (1202)3.3.1.IR analysis (1202)3.3.2.X-ray analysis (1203)3.4.Distribution of molecular orientation (1203)4.Analysis of experimental results (1203)4.1.Injection molding tests (1203)4.2.Morphology distribution along thickness direction (1204)4.2.1.Optical microscopy (1204)4.2.2.SEM and AFM analysis (1204)4.3.Morphology distribution alongﬂow direction (1208)4.4.Distribution of crystallinity (1210)4.4.1.Distribution of crystallinity along thickness direction (1210)4.4.2.Crystallinity distribution alongﬂow direction (1212)4.5.Distribution of molecular orientation (1212)4.5.1.Orientation along thickness direction (1212)4.5.2.Orientation alongﬂow direction (1213)4.5.3.Direction of orientation (1214)5.Simulation (1214)5.1.Pressure curves (1215)5.2.Morphology distribution (1215)5.3.Molecular orientation (1216)5.3.1.Molecular orientation distribution along thickness direction (1216)5.3.2.Molecular orientation distribution alongﬂow direction (1216)5.3.3.Direction of orientation (1217)5.4.Crystallinity distribution (1217)6.Conclusions (1217)References (1219)1.IntroductionInjection molding is one of the most widely employed methods for manufacturing polymeric products.Three main steps are recognized in the molding:ﬁlling,packing/holding and cooling.During theﬁlling stage,a hot polymer melt rapidlyﬁlls a cold mold reproducing a cavity of the desired product shape. During the packing/holding stage,the pressure is raised and extra material is forced into the mold to compensate for the effects that both temperature decrease and crystallinity development determine on density during solidiﬁcation.The cooling stage starts at the solidiﬁcation of a thin section at cavity entrance (gate),starting from that instant no more material can enter or exit from the mold impression and holding pressure can be released.When the solid layer on the mold surface reaches a thickness sufﬁcient to assure required rigidity,the product is ejected from the mold.Due to the thermomechanical history experienced by the polymer during processing,macromolecules in injection-molded objects present a local order.This order is referred to as‘morphology’which literally means‘the study of the form’where form stands for the shape and arrangement of parts of the object.When referred to polymers,the word morphology is adopted to indicate:–crystallinity,which is the relative volume occupied by each of the crystalline phases,including mesophases;–dimensions,shape,distribution and orientation of the crystallites;–orientation of amorphous phase.R.Pantani et al./Prog.Polym.Sci.30(2005)1185–1222 1186R.Pantani et al./Prog.Polym.Sci.30(2005)1185–12221187Apart from the scientiﬁc interest in understandingthe mechanisms leading to different order levels inside a polymer,the great technological importance of morphology relies on the fact that polymer character-istics (above all mechanical,but also optical,electrical,transport and chemical)are to a great extent affected by morphology.For instance,crystallinity has a pro-nounced effect on the mechanical properties of the bulk material since crystals are generally stiffer than amorphous material,and also orientation induces anisotropy and other changes in mechanical properties.In this work,a thorough analysis of the effect of injection molding operative conditions on morphology distribution in moldings with particular reference to crystalline materials is performed.The aim of the paper is twofold:ﬁrst,to outline the state of the art on the subject;second,to present an example of the characterization required for asatisfactorilyR.Pantani et al./Prog.Polym.Sci.30(2005)1185–12221188understanding and description of the phenomena, starting from material description,passing through the monitoring of the process cycle and arriving to a deep analysis of morphology distribution inside the mold-ings.To these purposes,fully characterized injection molding tests were performed using an isotactic polypropylene,previously carefully characterized as far as most of properties of interest,in particular quiescent nucleation density,spherulitic growth rate and rheological properties(viscosity and relaxation time)were determined.The resulting moldings mor-phology(in terms of distribution of crystallinity degree, molecular orientation and crystals structure and dimensions)was analyzed by adopting different experimental techniques(optical,electronic and atomic force microscopy,IR and WAXS analysis).Final morphological characteristics of the samples were compared with the predictions of a simulation code developed at University of Salerno for the simulation of the injection molding process.The effects of both injectionﬂow rate and mold temperature were analyzed.1.1.Morphology distribution in injection molded iPP parts:state of the artFrom many experimental observations,it is shown that a highly oriented lamellar crystallite microstructure, usually referred to as‘skin layer’forms close to the surface of injection molded articles of semi-crystalline polymers.Far from the wall,the melt is allowed to crystallize three dimensionally to form spherulitic structures.Relative dimensions and morphology of both skin and core layers are dependent on local thermo-mechanical history,which is characterized on the surface by high stress levels,decreasing to very small values toward the core region.As a result,the skin and the core reveal distinct characteristics across the thickness and also along theﬂow path[1].Structural and morphological characterization of the injection molded polypropylene has attracted the interest of researchers in the past three decades.In the early seventies,Kantz et al.[2]studied the morphology of injection molded iPP tensile bars by using optical microscopy and X-ray diffraction.The microscopic results revealed the presence of three distinct crystalline zones on the cross-section:a highly oriented non-spherulitic skin;a shear zone with molecular chains oriented essentially parallel to the injection direction;a spherulitic core with essentially no preferred orientation.The X-ray diffraction studies indicated that the skin layer contains biaxially oriented crystallites due to the biaxial extensionalﬂow at theﬂow front.A similar multilayered morphology was also reported by Menges et al.[3].Later on,Fujiyama et al.[4] investigated the skin–core morphology of injection molded iPP samples using X-ray Small and Wide Angle Scattering techniques,and suggested that the shear region contains shish–kebab structures.The same shish–kebab structure was observed by Wenig and Herzog in the shear region of their molded samples[5].A similar investigation was conducted by Titomanlio and co-workers[6],who analyzed the morphology distribution in injection moldings of iPP. They observed a skin–core morphology distribution with an isotropic spherulitic core,a skin layer characterized by aﬁne crystalline structure and an intermediate layer appearing as a dark band in crossed polarized light,this layer being characterized by high crystallinity.Kalay and Bevis[7]pointed out that,although iPP crystallizes essentially in the a-form,a small amount of b-form can be found in the skin layer and in the shear region.The amount of b-form was found to increase by effect of high shear rates[8].A wide analysis on the effect of processing conditions on the morphology of injection molded iPP was conducted by Viana et al.[9]and,more recently, by Mendoza et al.[10].In particular,Mendoza et al. report that the highest level of crystallinity orientation is found inside the shear zone and that a high level of orientation was also found in the skin layer,with an orientation angle tilted toward the core.It is rather difﬁcult to theoretically establish the relationship between the observed microstructure and processing conditions.Indeed,a model of the injection molding process able to predict morphology distribution in theﬁnal samples is not yet available,even if it would be of enormous strategic importance.This is mainly because a complete understanding of crystallization kinetics in processing conditions(high cooling rates and pressures,strong and complexﬂowﬁelds)has not yet been reached.In this section,the most relevant aspects for process modeling and morphology development are identiﬁed. In particular,a successful path leading to a reliable description of morphology evolution during polymer processing should necessarily pass through:–a good description of morphology evolution under quiescent conditions(accounting all competing crystallization processes),including the range of cooling rates characteristic of processing operations (from1to10008C/s);R.Pantani et al./Prog.Polym.Sci.30(2005)1185–12221189–a description capturing the main features of melt morphology(orientation and stretch)evolution under processing conditions;–a good coupling of the two(quiescent crystallization and orientation)in order to capture the effect of crystallinity on viscosity and the effect ofﬂow on crystallization kinetics.The points listed above outline the strategy to be followed in order to achieve the basic understanding for a satisfactory description of morphology evolution during all polymer processing operations.In the following,the state of art for each of those points will be analyzed in a dedicated section.1.1.1.Modeling of the injection molding processTheﬁrst step in the prediction of the morphology distribution within injection moldings is obviously the thermo-mechanical simulation of the process.Much of the efforts in the past were focused on the prediction of pressure and temperature evolution during the process and on the prediction of the melt front advancement [11–15].The simulation of injection molding involves the simultaneous solution of the mass,energy and momentum balance equations.Theﬂuid is non-New-tonian(and viscoelastic)with all parameters dependent upon temperature,pressure,crystallinity,which are all function of pressibility cannot be neglected as theﬂow during the packing/holding step is determined by density changes due to temperature, pressure and crystallinity evolution.Indeed,apart from some attempts to introduce a full 3D approach[16–19],the analysis is currently still often restricted to the Hele–Shaw(or thinﬁlm) approximation,which is warranted by the fact that most injection molded parts have the characteristic of being thin.Furthermore,it is recognized that the viscoelastic behavior of the polymer only marginally inﬂuences theﬂow kinematics[20–22]thus the melt is normally considered as a non-Newtonian viscousﬂuid for the description of pressure and velocity gradients evolution.Some examples of adopting a viscoelastic constitutive equation in the momentum balance equations are found in the literature[23],but the improvements in accuracy do not justify a considerable extension of computational effort.It has to be mentioned that the analysis of some features of kinematics and temperature gradients affecting the description of morphology need a more accurate description with respect to the analysis of pressure distributions.Some aspects of the process which were often neglected and may have a critical importance are the description of the heat transfer at polymer–mold interface[24–26]and of the effect of mold deformation[24,27,28].Another aspect of particular interest to the develop-ment of morphology is the fountainﬂow[29–32], which is often neglected being restricted to a rather small region at theﬂow front and close to the mold walls.1.1.2.Modeling of the crystallization kineticsIt is obvious that the description of crystallization kinetics is necessary if theﬁnal morphology of the molded object wants to be described.Also,the development of a crystalline degree during the process inﬂuences the evolution of all material properties like density and,above all,viscosity(see below).Further-more,crystallization kinetics enters explicitly in the generation term of the energy balance,through the latent heat of crystallization[26,33].It is therefore clear that the crystallinity degree is not only a result of simulation but also(and above all)a phenomenon to be kept into account in each step of process modeling.In spite of its dramatic inﬂuence on the process,the efforts to simulate the injection molding of semi-crystalline polymers are crude in most of the commercial software for processing simulation and rather scarce in the ﬂeur and Kamal[34],Papatanasiu[35], Titomanlio et al.[15],Han and Wang[36],Ito et al.[37],Manzione[38],Guo and Isayev[26],and Hieber [25]adopted the following equation(Kolmogoroff–Avrami–Evans,KAE)to predict the development of crystallinityd xd tZð1K xÞd d cd t(1)where x is the relative degree of crystallization;d c is the undisturbed volume fraction of the crystals(if no impingement would occur).A signiﬁcant improvement in the prediction of crystallinity development was introduced by Titoman-lio and co-workers[39]who kept into account the possibility of the formation of different crystalline phases.This was done by assuming a parallel of several non-interacting kinetic processes competing for the available amorphous volume.The evolution of each phase can thus be described byd x id tZð1K xÞd d c id t(2)where the subscript i stands for a particular phase,x i is the relative degree of crystallization,x ZPix i and d c iR.Pantani et al./Prog.Polym.Sci.30(2005)1185–1222 1190is the expectancy of volume fraction of each phase if no impingement would occur.Eq.(2)assumes that,for each phase,the probability of the fraction increase of a single crystalline phase is simply the product of the rate of growth of the corresponding undisturbed volume fraction and of the amount of available amorphous fraction.By summing up the phase evolution equations of all phases(Eq.(2))over the index i,and solving the resulting differential equation,one simply obtainsxðtÞZ1K exp½K d cðtÞ (3)where d c Z Pid c i and Eq.(1)is recovered.It was shown by Coccorullo et al.[40]with reference to an iPP,that the description of the kinetic competition between phases is crucial to a reliable prediction of solidiﬁed structures:indeed,it is not possible to describe iPP crystallization kinetics in the range of cooling rates of interest for processing(i.e.up to several hundreds of8C/s)if the mesomorphic phase is neglected:in the cooling rate range10–1008C/s, spherulite crystals in the a-phase are overcome by the formation of the mesophase.Furthermore,it has been found that in some conditions(mainly at pressures higher than100MPa,and low cooling rates),the g-phase can also form[41].In spite of this,the presence of different crystalline phases is usually neglected in the literature,essentially because the range of cooling rates investigated for characterization falls in the DSC range (well lower than typical cooling rates of interest for the process)and only one crystalline phase is formed for iPP at low cooling rates.It has to be noticed that for iPP,which presents a T g well lower than ambient temperature,high values of crystallinity degree are always found in solids which passed through ambient temperature,and the cooling rate can only determine which crystalline phase forms, roughly a-phase at low cooling rates(below about 508C/s)and mesomorphic phase at higher cooling rates.The most widespread approach to the description of kinetic constant is the isokinetic approach introduced by Nakamura et al.According to this model,d c in Eq.(1)is calculated asd cðtÞZ ln2ðt0KðTðsÞÞd s2 435n(4)where K is the kinetic constant and n is the so-called Avrami index.When introduced as in Eq.(4),the reciprocal of the kinetic constant is a characteristic time for crystallization,namely the crystallization half-time, t05.If a polymer is cooled through the crystallization temperature,crystallization takes place at the tempera-ture at which crystallization half-time is of the order of characteristic cooling time t q deﬁned ast q Z D T=q(5) where q is the cooling rate and D T is a temperature interval over which the crystallization kinetic constant changes of at least one order of magnitude.The temperature dependence of the kinetic constant is modeled using some analytical function which,in the simplest approach,is described by a Gaussian shaped curve:KðTÞZ K0exp K4ln2ðT K T maxÞ2D2(6)The following Hoffman–Lauritzen expression[42] is also commonly adopted:K½TðtÞ Z K0exp KUÃR$ðTðtÞK T NÞ!exp KKÃ$ðTðtÞC T mÞ2TðtÞ2$ðT m K TðtÞÞð7ÞBoth equations describe a bell shaped curve with a maximum which for Eq.(6)is located at T Z T max and for Eq.(7)lies at a temperature between T m(the melting temperature)and T N(which is classically assumed to be 308C below the glass transition temperature).Accord-ing to Eq.(7),the kinetic constant is exactly zero at T Z T m and at T Z T N,whereas Eq.(6)describes a reduction of several orders of magnitude when the temperature departs from T max of a value higher than2D.It is worth mentioning that only three parameters are needed for Eq.(6),whereas Eq.(7)needs the deﬁnition ofﬁve parameters.Some authors[43,44]couple the above equations with the so-called‘induction time’,which can be deﬁned as the time the crystallization process starts, when the temperature is below the equilibrium melting temperature.It is normally described as[45]Dt indDtZðT0m K TÞat m(8)where t m,T0m and a are material constants.It should be mentioned that it has been found[46,47]that there is no need to explicitly incorporate an induction time when the modeling is based upon the KAE equation(Eq.(1)).1.1.3.Modeling of the morphology evolutionDespite of the fact that the approaches based on Eq.(4)do represent a signiﬁcant step toward the descriptionR.Pantani et al./Prog.Polym.Sci.30(2005)1185–12221191of morphology,it has often been pointed out in the literature that the isokinetic approach on which Nakamura’s equation (Eq.(4))is based does not describe details of structure formation [48].For instance,the well-known experience that,with many polymers,the number of spherulites in the ﬁnal solid sample increases strongly with increasing cooling rate,is indeed not taken into account by this approach.Furthermore,Eq.(4)describes an increase of crystal-linity (at constant temperature)depending only on the current value of crystallinity degree itself,whereas it is expected that the crystallization rate should depend also on the number of crystalline entities present in the material.These limits are overcome by considering the crystallization phenomenon as the consequence of nucleation and growth.Kolmogoroff’s model [49],which describes crystallinity evolution accounting of the number of nuclei per unit volume and spherulitic growth rate can then be applied.In this case,d c in Eq.(1)is described asd ðt ÞZ C m ðt 0d N ðs Þd s$ðt sG ðu Þd u 2435nd s (9)where C m is a shape factor (C 3Z 4/3p ,for spherical growth),G (T (t ))is the linear growth rate,and N (T (t ))is the nucleation density.The following Hoffman–Lauritzen expression is normally adopted for the growth rateG ½T ðt Þ Z G 0exp KUR $ðT ðt ÞK T N Þ!exp K K g $ðT ðt ÞC T m Þ2T ðt Þ2$ðT m K T ðt ÞÞð10ÞEqs.(7)and (10)have the same form,however the values of the constants are different.The nucleation mechanism can be either homo-geneous or heterogeneous.In the case of heterogeneous nucleation,two equations are reported in the literature,both describing the nucleation density as a function of temperature [37,50]:N ðT ðt ÞÞZ N 0exp ½j $ðT m K T ðt ÞÞ (11)N ðT ðt ÞÞZ N 0exp K 3$T mT ðt ÞðT m K T ðt ÞÞ(12)In the case of homogeneous nucleation,the nucleation rate rather than the nucleation density is function of temperature,and a Hoffman–Lauritzen expression isadoptedd N ðT ðt ÞÞd t Z N 0exp K C 1ðT ðt ÞK T N Þ!exp KC 2$ðT ðt ÞC T m ÞT ðt Þ$ðT m K T ðt ÞÞð13ÞConcentration of nucleating particles is usually quite signiﬁcant in commercial polymers,and thus hetero-geneous nucleation becomes the dominant mechanism.When Kolmogoroff’s approach is followed,the number N a of active nuclei at the end of the crystal-lization process can be calculated as [48]N a ;final Zðt final 0d N ½T ðs Þd sð1K x ðs ÞÞd s (14)and the average dimension of crystalline structures can be attained by geometrical considerations.Pantani et al.[51]and Zuidema et al.[22]exploited this method to describe the distribution of crystallinity and the ﬁnal average radius of the spherulites in injection moldings of polypropylene;in particular,they adopted the following equationR Z ﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃ3x a ;final 4p N a ;final 3s (15)A different approach is also present in the literature,somehow halfway between Nakamura’s and Kolmo-goroff’s models:the growth rate (G )and the kinetic constant (K )are described independently,and the number of active nuclei (and consequently the average dimensions of crystalline entities)can be obtained by coupling Eqs.(4)and (9)asN a ðT ÞZ 3ln 24p K ðT ÞG ðT Þ 3(16)where heterogeneous nucleation and spherical growth is assumed (Avrami’s index Z 3).Guo et al.[43]adopted this approach to describe the dimensions of spherulites in injection moldings of polypropylene.1.1.4.Modeling of the effect of crystallinity on rheology As mentioned above,crystallization has a dramatic inﬂuence on material viscosity.This phenomenon must obviously be taken into account and,indeed,the solidiﬁcation of a semi-crystalline material is essen-tially caused by crystallization rather than by tempera-ture in normal processing conditions.Despite of the importance of the subject,the relevant literature on the effect of crystallinity on viscosity isR.Pantani et al./Prog.Polym.Sci.30(2005)1185–12221192rather scarce.This might be due to the difﬁculties in measuring simultaneously rheological properties and crystallinity evolution during the same tests.Apart from some attempts to obtain simultaneous measure-ments of crystallinity and viscosity by special setups [52,53],more often viscosity and crystallinity are measured during separate tests having the same thermal history,thus greatly simplifying the experimental approach.Nevertheless,very few works can be retrieved in the literature in which(shear or complex) viscosity can be somehow linked to a crystallinity development.This is the case of Winter and co-workers [54],Vleeshouwers and Meijer[55](crystallinity evolution can be drawn from Swartjes[56]),Boutahar et al.[57],Titomanlio et al.[15],Han and Wang[36], Floudas et al.[58],Wassner and Maier[59],Pantani et al.[60],Pogodina et al.[61],Acierno and Grizzuti[62].All the authors essentially agree that melt viscosity experiences an abrupt increase when crystallinity degree reaches a certain‘critical’value,x c[15]. However,little agreement is found in the literature on the value of this critical crystallinity degree:assuming that x c is reached when the viscosity increases of one order of magnitude with respect to the molten state,it is found in the literature that,for iPP,x c ranges from a value of a few percent[15,62,60,58]up to values of20–30%[58,61]or even higher than40%[59,54,57].Some studies are also reported on the secondary effects of relevant variables such as temperature or shear rate(or frequency)on the dependence of crystallinity on viscosity.As for the effect of temperature,Titomanlio[15]found for an iPP that the increase of viscosity for the same crystallinity degree was higher at lower temperatures,whereas Winter[63] reports the opposite trend for a thermoplastic elasto-meric polypropylene.As for the effect of shear rate,a general agreement is found in the literature that the increase of viscosity for the same crystallinity degree is lower at higher deformation rates[62,61,57].Essentially,the equations adopted to describe the effect of crystallinity on viscosity of polymers can be grouped into two main categories:–equations based on suspensions theories(for a review,see[64]or[65]);–empirical equations.Some of the equations adopted in the literature with regard to polymer processing are summarized in Table1.Apart from Eq.(17)adopted by Katayama and Yoon [66],all equations predict a sharp increase of viscosity on increasing crystallinity,sometimes reaching inﬁnite (Eqs.(18)and(21)).All authors consider that the relevant variable is the volume occupied by crystalline entities(i.e.x),even if the dimensions of the crystals should reasonably have an effect.1.1.5.Modeling of the molecular orientationOne of the most challenging problems to present day polymer science regards the reliable prediction of molecular orientation during transformation processes. Indeed,although pressure and velocity distribution during injection molding can be satisfactorily described by viscous models,details of the viscoelastic nature of the polymer need to be accounted for in the descriptionTable1List of the most used equations to describe the effect of crystallinity on viscosityEquation Author Derivation Parameters h=h0Z1C a0x(17)Katayama[66]Suspensions a Z99h=h0Z1=ðx K x cÞa0(18)Ziabicki[67]Empirical x c Z0.1h=h0Z1C a1expðK a2=x a3Þ(19)Titomanlio[15],also adopted byGuo[68]and Hieber[25]Empiricalh=h0Z expða1x a2Þ(20)Shimizu[69],also adopted byZuidema[22]and Hieber[25]Empiricalh=h0Z1Cðx=a1Þa2=ð1Kðx=a1Þa2Þ(21)Tanner[70]Empirical,basedon suspensionsa1Z0.44for compact crystallitesa1Z0.68for spherical crystallitesh=h0Z expða1x C a2x2Þ(22)Han[36]Empiricalh=h0Z1C a1x C a2x2(23)Tanner[71]Empirical a1Z0.54,a2Z4,x!0.4h=h0Zð1K x=a0ÞK2(24)Metzner[65],also adopted byTanner[70]Suspensions a Z0.68for smooth spheresR.Pantani et al./Prog.Polym.Sci.30(2005)1185–12221193。

LTPS制程与技术发展

資料來源：工研院電子所
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Poly-Si/α-Si特性比較
• α-Si TFT LCD的結構簡單化和畫面高精
細化。 • P-Si TFT LCD是崁入不同功能的IC於玻
璃基板上，減少模組工程上所使用IC的數量，換言之，模組接點減少，可靠度提升。
資料來源：工研院電子所
資料來源：工研院電子所
資料來源：工研院電子所
資料來源：工研院電子所
資料來源：工研院電子所
資料來源：工研院電子所
資料來源：工研院電子所
資料來源：工研院電子所
專有名詞(1)
• 準分子雷射(Excimer Laser)：
–準分子是激發態的雙量體(Dimer)，Excimer 為Excited Dimer的英文縮寫
• 低溫Poly-Si結晶化的技術主要是準分子雷射退火法(ELA)
資料來源：工研院電子所
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資料來源：工研院電子所
標準化製作過程(10)
10. 摻雜工程：
• 為了Poly-Si薄膜之源極和汲極層的低電阻化，及使關閉(Off)電壓值提高，導入高濃度不純物的工程
• 方法：
液晶胞製程(4)
4. 封合劑印刷形成工程：
• 經配向面磨處理後之Array下基板和CF上基板，任選其中一片基板之週邊封合部，將熱硬化型或紫外線硬化型環氧樹脂類的接著劑以網版印刷法或散佈法塗佈上去，然後進行100ºC左右的烘焙處理。
液晶胞製程(5)
5. 間隔物(Spacer)散佈工程： • 使上下兩片基板保持於5-7μm的液晶胞間
– 可獲得高的載體移動度 – 使電子訊號的傳送速度變快 – 動態畫質顯示清晰明亮。
標準化製作過程(1)

高迁移率金属氧化物半导体薄膜晶体管的研究进展

第 39 卷第 4 期2024 年 4 月Vol.39 No.4Apr. 2024液晶与显示Chinese Journal of Liquid Crystals and Displays高迁移率金属氧化物半导体薄膜晶体管的研究进展李强，葛春桥*，陈露，钟威平，梁齐莹，柳春锡，丁金铎（中山智隆新材料科技有限公司，广东中山 528459）摘要：基于金属氧化物半导体（MOS）的薄膜晶体管（TFT）由于较高的场效应迁移率（μFE）、极低的关断漏电流和大面积电性均匀等特点，已成为助推平板显示或柔性显示产业发展的一项关键技术。

经过30余年的研究，非晶铟镓锌氧化物（a-IGZO）率先替代非晶硅（a-Si）在TFT中得到推广应用。

然而，为了同时满足显示产业对更高生产效益、更佳显示性能（如高分辨率、高刷新率等）和更低功耗等多元升级要求，需要迁移率更高的MOS TFTs技术。

本文从固体物理学的角度，系统综述了MOS TFTs通过多元MOS材料实现高迁移率特性的研究进展，并讨论了迁移率与器件稳定性之间的关系。

最后，总结展望了MOS TFTs的现状和发展趋势。

关键词：金属氧化物半导体；薄膜晶体管；场效应迁移率；偏压稳定性中图分类号：TN321+.5 文献标识码：A doi：10.37188/CJLCD.2024-0032Research progress of high mobility metal oxide semiconductorthin film transistorsLI Qiang，GE Chunqiao*，CHEN Lu，ZHONG Weiping，LIANG Qiying，LIU Chunxi，DING Jinduo （Zhongshan Zhilong New Material Technology Co. Ltd.， Zhongshan 528459， China）Abstract：Thin-film transistor （TFT）based on metal oxide semiconductor （MOS）has become a key technology to boost the development of the flat panel display or flexible display industry due to their high field-effect mobility （μFE）， extremely low cut-off leakage current and good large-area electrical uniformity. After more than 30 years of research，amorphous indium gallium zinc oxide （a-IGZO）is the first to be popularized in TFT by replacing the amorphous silicon （a-Si）. However， in order to simultaneously meet the multiple upgrade requirements of the display industry for higher productivity，better display performance （such as high resolution， high refresh rate，etc.） and lower power consumption， MOS TFTs technology with higher mobility is required.From the perspective of solid-state physics，this paper reviews the research progress of MOS TFTs to achieve high mobility characteristics through multi-component MOS materials， and discusses the relationship between mobility and device stability. Finally， the status quo and development trend of MOS TFTs are summarized and prospected.文章编号：1007-2780（2024）04-0447-19收稿日期：2024-01-23；修订日期：2024-02-14.基金项目：中山市科技计划（No.LJ2021006，No.CXTD2022005，No.2022A1009）Supported by Zhongshan Science and Technology Development Plan（No.LJ2021006，No.CXTD2022005，No.2022A1009）*通信联系人，E-mail：gechunqiao@zhilong.pro第 39 卷液晶与显示Key words： metal oxide semiconductor； thin-film transistor； field-effect mobility； bias stability1 引言在各类消费电子和工业设备显示中，薄膜晶体管（TFT）驱动背板是保障显示屏幕稳定运行的核心部件。

有机薄膜晶体管

现状
最近几年，随着透明氧化物研究的深入，以ZnO、ZIO 等半导体材料作为活性层制作薄膜晶体管，因性能改进显著也吸引了越来越多的兴趣。器件制备工艺很广泛，比如： MBE、CVD、PLD 等，均有研究。ZnO-TFT 技术也取得了突破性进展。2003 年，Nomura等人使用单晶InGaO3 (ZnO)5 获得了迁移率为80 cm2V-1 s-1 的TFT 器件。美国杜邦公司采用真空蒸镀和掩膜挡板技术在聚酰亚铵柔性衬底上开发了ZnO-TFT，电子迁移率为50 cm2V-1 s-1。这是在聚酰亚铵柔性衬底上首次研制成功了高迁移率的 ZnO-TFT，这预示着在氧化物TFT领域新竞争的开始。 2005 年，Chiang H Q 等人利用ZIO 作为活性层制得开比为10^7 薄膜晶体管。2006 年，ChengH C等人利用 CBD 方法制得开关比为105 、迁移率为0.248cm2V1s-1 的TFT，这也显示出实际应用的可能。
薄膜技术在显示领域的发展
纵观信息时代迅猛发展的各项技术，不论网络技术与软件，还是通信技术、计算机技术，如果没有TFT-LCD（薄膜晶体管阵列）为代表的平板显示技术做人机交互界面，就构不成现在的信息社会。显示器件作为信息产业的重要组成部分正加速发展。传统的阴极射线(CRT)显示器件技术早己成熟，性能较好、价格越来越便宜，但因体积大、重量大、功耗大、对人的身体辐射较强等方面，限制了在更广泛的领域中应用。目前液晶显示器(LCD)以低电压、低功耗、适宜于电路集成、轻巧便携等优点而受到广泛研究与应用。液晶显示技术的发展经历了扭曲向列（TN-LCD）、超扭曲向列（STN-LCD）和薄膜晶体管阵列（TFT-LCD）三个重要的发展阶段。进入20 世纪90 年代后，LCD 技术发展开始进入高画质彩色图像显示的新阶段，有源矩阵的 TFT 液晶显示技术的性能取得了飞速发展，克服了STN 液晶显示器件在响应速度、视角、灰度调制等方面存在的不足，技术性能接近于CRT。

高熵合金

Microstructures and properties of high-entropyalloysYong Zhang a ,⇑,Ting Ting Zuo a ,Zhi Tang b ,Michael C.Gao c ,d ,Karin A.Dahmen e ,Peter K.Liaw b ,Zhao Ping Lu aa State Key Laboratory for Advanced Metals and Materials,University of Science and Technology Beijing,Beijing 100083,Chinab Department of Materials Science and Engineering,The University of Tennessee,Knoxville,TN 37996,USAc National Energy Technology Laboratory,1450Queen Ave SW,Albany,OR 97321,USAd URS Corporation,PO Box 1959,Albany,OR 97321-2198,USAe Department of Physics,University of Illinois at Urbana-Champaign,1110West Green Street,Urbana,IL 61801-3080,USA a r t i c l e i n f o Article history:Received 26September 2013Accepted 8October 2013Available online 1November 2013a b s t r a c tThis paper reviews the recent research and development of high-entropy alloys (HEAs).HEAs are loosely deﬁned as solid solutionalloys that contain more than ﬁve principal elements in equal ornear equal atomic percent (at.%).The concept of high entropyintroduces a new path of developing advanced materials withunique properties,which cannot be achieved by the conventionalmicro-alloying approach based on only one dominant element.Up to date,many HEAs with promising properties have beenreported, e.g.,high wear-resistant HEAs,Co 1.5CrFeNi 1.5Ti andAl 0.2Co 1.5CrFeNi 1.5Ti alloys;high-strength body-centered-cubic(BCC)AlCoCrFeNi HEAs at room temperature,and NbMoTaV HEAat elevated temperatures.Furthermore,the general corrosion resis-tance of the Cu 0.5NiAlCoCrFeSi HEA is much better than that of theconventional 304-stainless steel.This paper ﬁrst reviews HEA for-mation in relation to thermodynamics,kinetics,and processing.Physical,magnetic,chemical,and mechanical properties are thendiscussed.Great details are provided on the plastic deformation,fracture,and magnetization from the perspectives of cracklingnoise and Barkhausen noise measurements,and the analysis of ser-rations on stress–strain curves at speciﬁc strain rates or testingtemperatures,as well as the serrations of the magnetizationhysteresis loops.The comparison between conventional andhigh-entropy bulk metallic glasses is analyzed from the viewpointsof eutectic composition,dense atomic packing,and entropy of 0079-6425/$-see front matter Ó2013Elsevier Ltd.All rights reserved./10.1016/j.pmatsci.2013.10.001⇑Corresponding author.Tel.:+8601062333073;fax:+8601062333447.E-mail address:drzhangy@ (Y.Zhang).2Y.Zhang et al./Progress in Materials Science61(2014)1–93mixing.Glass forming ability and plastic properties of high-entropy bulk metallic glasses are also discussed.Modeling tech-niques applicable to HEAs are introduced and discussed,such asab initio molecular dynamics simulations and CALPHAD modeling.Finally,future developments and potential new research directionsfor HEAs are proposed.Ó2013Elsevier Ltd.All rights reserved. Contents1.Introduction (3)1.1.Four core effects (4)1.1.1.High-entropy effect (4)1.1.2.Sluggish diffusion effect (5)1.1.3.Severe lattice-distortion effect (6)1.1.4.Cocktail effect (7)1.2.Key research topics (9)1.2.1.Mechanical properties compared with other alloys (10)1.2.2.Underlying mechanisms for mechanical properties (11)1.2.3.Alloy design and preparation for HEAs (11)1.2.4.Theoretical simulations for HEAs (12)2.Thermodynamics (12)2.1.Entropy (13)2.2.Thermodynamic considerations of phase formation (15)2.3.Microstructures of HEAs (18)3.Kinetics and alloy preparation (23)3.1.Preparation from the liquid state (24)3.2.Preparation from the solid state (29)3.3.Preparation from the gas state (30)3.4.Electrochemical preparation (34)4.Properties (34)4.1.Mechanical behavior (34)4.1.1.Mechanical behavior at room temperature (35)4.1.2.Mechanical behavior at elevated temperatures (38)4.1.3.Mechanical behavior at cryogenic temperatures (45)4.1.4.Fatigue behavior (46)4.1.5.Wear behavior (48)4.1.6.Summary (49)4.2.Physical behavior (50)4.3.Biomedical,chemical and other behaviors (53)5.Serrations and deformation mechanisms (55)5.1.Serrations for HEAs (56)5.2.Barkhausen noise for HEAs (58)5.3.Modeling the Serrations of HEAs (61)5.4.Deformation mechanisms for HEAs (66)6.Glass formation in high-entropy alloys (67)6.1.High-entropy effects on glass formation (67)6.1.1.The best glass former is located at the eutectic compositions (67)6.1.2.The best glass former is the composition with dense atomic packing (67)6.1.3.The best glass former has high entropy of mixing (67)6.2.GFA for HEAs (68)6.3.Properties of high-entropy BMGs (70)7.Modeling and simulations (72)7.1.DFT calculations (73)7.2.AIMD simulations (75)7.3.CALPHAD modeling (80)8.Future development and research (81)Y.Zhang et al./Progress in Materials Science61(2014)1–9338.1.Fundamental understanding of HEAs (82)8.2.Processing and characterization of HEAs (83)8.3.Applications of HEAs (83)9.Summary (84)Disclaimer (85)Acknowledgements (85)References (85)1.IntroductionRecently,high-entropy alloys(HEAs)have attracted increasing attentions because of their unique compositions,microstructures,and adjustable properties[1–31].They are loosely deﬁned as solid solution alloys that contain more thanﬁve principal elements in equal or near equal atomic percent (at.%)[32].Normally,the atomic fraction of each component is greater than5at.%.The multi-compo-nent equi-molar alloys should be located at the center of a multi-component phase diagram,and their conﬁguration entropy of mixing reaches its maximum(R Ln N;R is the gas constant and N the number of component in the system)for a solution phase.These alloys are deﬁned as HEAs by Yeh et al.[2], and named by Cantor et al.[1,33]as multi-component alloys.Both refer to the same concept.There are also some other names,such as multi-principal-elements alloys,equi-molar alloys,equi-atomic ratio alloys,substitutional alloys,and multi-component alloys.Cantor et al.[1,33]pointed out that a conventional alloy development strategy leads to an enor-mous amount of knowledge about alloys based on one or two components,but little or no knowledge about alloys containing several main components in near-equal proportions.Theoretical and experi-mental works on the occurrence,structure,and properties of crystalline phases have been restricted to alloys based on one or two main components.Thus,the information and understanding are highly developed on alloys close to the corners and edges of a multi-component phase diagram,with much less knowledge about alloys located at the center of the phase diagram,as shown schematically for ternary and quaternary alloy systems in Fig.1.1.This imbalance is signiﬁcant for ternary alloys but becomes rapidly much more pronounced as the number of components increases.For most quater-nary and other higher-order systems,information about alloys at the center of the phase diagram is virtually nonexistent except those HEA systems that have been reported very recently.In the1990s,researchers began to explore for metallic alloys with super-high glass-forming ability (GFA).Greer[29]proposed a confusion principle,which states that the more elements involved,the lower the chance that the alloy can select viable crystal structures,and thus the greater the chanceand quaternary alloy systems,showing regions of the phase diagram thatand relatively less well known(white)near the center[33].solid-solutions even though the cooling rate is very high,e.g.,alloys of CuCoNiCrAlFeTiV,FeCrMnNiCo,CoCrFeNiCu,AlCoCrFeNi,NbMoTaWV,etc.[1,2,12–14].The yield strength of the body-centered cubic (BCC)HEAs can be rather high [12],usually compa-rable to BMGs [12].Moreover,the high strength can be kept up to 800K or higher for some HEAs based on 3d transition metals [14].In contrast,BMGs can only keep their high strength below their glass-transition temperature.1.1.Four core effectsBeing different from the conventional alloys,compositions in HEAs are complex due to the equi-molar concentration of each component.Yeh [37]summarized mainly four core effects for HEAs,that is:(1)Thermodynamics:high-entropy effects;(2)Kinetics:sluggish diffusion;(3)Structures:severe lattice distortion;and (4)Properties:cocktail effects.We will discuss these four core effects separately.1.1.1.High-entropy effectThe high-entropy effects,which tend to stabilize the high-entropyphases,e.g.,solid-solution phases,were ﬁrstly proposed by Yeh [9].The effects were very counterintuitive because it was ex-pected that intermetallic compound phases may form for those equi-or near equi-atomic alloy com-positions which are located at the center of the phase diagrams (for example,a monoclinic compound AlCeCo forms in the center of Al–Ce–Co system [38]).According to the Gibbs phase rule,the number of phases (P )in a given alloy at constant pressure in equilibrium condition is:P ¼C þ1ÀF ð1-1Þwhere C is the number of components and F is the maximum number of thermodynamic degrees of freedom in the system.In the case of a 6-component system at given pressure,one might expect a maximum of 7equilibrium phases at an invariant reaction.However,to our surprise,HEAs form so-lid-solution phases rather than intermetallic phases [1,2,4,17].This is not to say that all multi-compo-nents in equal molar ratio will form solid solution phases at the center of the phase diagram.In fact,only carefully chosen compositions that satisfy the HEA-formation criteria will form solid solutions instead of intermetallic compounds.The solid-solution phase,according to the classical physical-metallurgy theory,is also called a ter-minal solid solution.The solid-solution phase is based on one element,which is called the solvent,and contains other minor elements,which are called the solutes.In HEAs,it is very difﬁcult to differentiate the solvent from the solute because of their equi-molar portions.Many researchers reported that the multi-principal-element alloys can only form simple phases of body-centered-cubic (BCC)or face-cen-tered-cubic (FCC)solid solutions,and the number of phases formed is much fewer than the maximum number of phases that the Gibbs phase rule allows [9,23].This feature also indicates that the high en-tropy of the alloys tends to expand the solution limits between the elements,which may further con-ﬁrm the high-entropy effects.The high-entropy effect is mainly used to explain the multi-principal-element solid solution.According to the maximum entropy production principle (MEPP)[39],high entropy tends to stabilize the high-entropy phases,i.e.,solid-solution phases,rather than intermetallic phases.Intermetallics are usually ordered phases with lower conﬁgurational entropy.For stoichiometric intermetallic com-pounds,their conﬁgurational entropy is zero.Whether a HEA of single solid solution phase is in its equilibrium has been questioned in the sci-entiﬁc community.There have been accumulated evidences to show that the high entropy of mixing truly extends the solubility limits of solid solution.For example,Lucas et al.[40]recently reported ab-sence of long-range chemical ordering in equi-molar FeCoCrNi alloy that forms a disordered FCC struc-ture.On the other hand,it was reported that some equi-atomic compositions such as AlCoCrCuFeNi contain several phases of different compositions when cooling slowly from the melt [15],and thus it is controversial whether they can be still classiﬁed as HEA.The empirical rules in guiding HEA for-mation are addressed in Section 2,which includes atomic size difference and heat of mixing.4Y.Zhang et al./Progress in Materials Science 61(2014)1–93Y.Zhang et al./Progress in Materials Science61(2014)1–935 1.1.2.Sluggish diffusion effectThe sluggish diffusion effect here is compared with that of the conventional alloys rather than the bulk-glass-forming alloys.Recently,Yeh[9]studied the vacancy formation and the composition par-tition in HEAs,and compared the diffusion coefﬁcients for the elements in pure metals,stainless steels, and HEAs,and found that the order of diffusion rates in the three types of alloy systems is shown be-low:Microstructures of an as-cast CuCoNiCrAlFe alloy.(A)SEM micrograph of an etched alloy withBCC and ordered BCC phases)and interdendrite(an FCC phase)structures.(B)TEMplate,70-nm wide,a disordered BCC phase(A2),lattice constant,2.89A;(B-b)aphase(B2),lattice constant,2.89A;(B-c)nanoprecipitation in a spinodal plate,7nm(B-d)nanoprecipitation in an interspinodal plate,3nm in diameter,a disorderedarea diffraction(SAD)patterns of B,Ba,and Bb with zone axes of BCC[01[011],respectively[2].illustration of intrinsic lattice distortion effects on Bragg diffraction:(a)perfect latticewith solid solutions of different-sized atoms,which are expected to randomly distribute statistical average probability of occupancy;(c)temperature and distortion effectsY.Zhang et al./Progress in Materials Science61(2014)1–937 the intensities further drop beyond the thermal effect with increasing the number of constituent prin-cipal elements.An intrinsic lattice distortion effect caused by the addition of multi-principal elements with different atomic sizes is expected for the anomalous decrease in the XRD intensities.The math-ematical treatment of this distortion effect for the modiﬁcation of the XRD structure factor is formu-lated to be similar to that of the thermal effect,as shown in Fig.1.3[41].The larger roughness of the atomic planes makes the intensity of the XRD for HEAs much lower than that for the single-element solid.The severe lattice distortion is also used to explain the high strength of HEAs,especially the BCC-structured HEAs[4,12,23].The severe lattice-distortion effect is also related to the tensile brittle-ness and the slower kinetics of HEAs[2,9,11].However,the authors also noticed that single-phase FCC-structured HEAs have very low strength[7],which certainly cannot be explained by the severe lattice distortion argument.Fundamental studies in quantiﬁcation of lattice distortion of HEAs are needed.1.1.4.Cocktail effectThe cocktail-party effect was usually used as a term in the acousticsﬁeld,which have been used to describe the ability to focus one’s listening attention on a single talker among a mixture of conversa-tions and background noises,ignoring other conversations.For metallic alloys,the effect indicates that the unexpected properties can be obtained after mixing many elements,which could not be obtained from any one independent element.The cocktail effect for metallic alloys wasﬁrst mentioned by Ranganathan[42],which has been subsequently conﬁrmed in the mechanical and physical properties [12,13,15,18,35,43].The cocktail effect implies that the alloy properties can be greatly adjusted by the composition change and alloying,as shown in Fig.1.4,which indicates that the hardness of HEAs can be dramat-ically changed by adjusting the Al content in the CoCrCuNiAl x HEAs.With the increase of the Al con-lattice constants of a CuCoNiCrAl x Fe alloy system with different x values:(A)hardnessconstants of an FCC phase,(C)lattice constants of a BCC phase[2].CoNiCrAl x Fe alloy system with different x values,the Cu-free alloy has lower hardness.CoCrCuFeNiAl x[15,45].Cu forms isomorphous solid solution with Ni but it is insoluble in Co,Cr and Fe;it dissolves about20at.%Al but also forms various stable intermetallic compounds with Al.Fig.1.6exhibits the hardness of some reported HEAs in the descending order with stainless steels as benchmark.The MoTiVFeNiZrCoCr alloy has a very high value of hardness of over800HV while CoCrFeNiCu is very soft with a value of less than200HV.Fig.1.7compares the speciﬁc strength,which yield strength over the density of the materials,and the density amongalloys,polymers and foam materials[5].We can see that HEAs have densitieshigh values of speciﬁc strength(yield strength/density).This is partiallyHEAs usually contain mainly the late transitional elements whoselightweight HEAs have much more potential because lightweightdensity of the resultant alloys will be lowered signiﬁcantly.Fig.1.8strength of HEAs vs.Young’s modulus compared with conventional alloys.highest speciﬁc strength and their Young’s modulus can be variedrange of hardness for HEAs,compared with17–4PH stainless steel,Hastelloy,andYield strength,r y,vs.density,q.HEAs(dark dashed circle)compared with other materials,particularly structural Grey dashed contours(arrow indication)label the speciﬁc strength,r y/q,from low(right bottom)to high(left top).among the materials with highest strength and speciﬁc strength[5].Speciﬁc-yield strength vs.Young’s modulus:HEAs compared with other materials,particularly structural alloys.among the materials with highest speciﬁc strength and with a wide range of Young’s modulus[5].range.This observation may indicate that the modulus of HEAs can be more easily adjusted than con-ventional alloys.In addition to the high speciﬁc strength,other properties such as high hydrogen stor-age property are also reported[46].1.2.Key research topicsTo understand the fundamentals of HEAs is a challenge to the scientists in materials science and relatedﬁelds because of lack of thermodynamic and kinetic data for multi-component systems in the center of phase diagrams.The phase diagrams are usually available only for the binary and ternary alloys.For HEAs,no complete phase diagrams are currently available to directly assist designing the10Y.Zhang et al./Progress in Materials Science61(2014)1–93alloy with desirable micro-and nanostructures.Recently,Yang and Zhang[28]proposed the X param-eter to design the solid-solution phase HEAs,which should be used combing with the parameter of atomic-size difference.This strategy may provide a starting point prior to actual experiments.The plastic deformation and fracture mechanisms of HEAs are also new because the high-entropy solid solutions contain high contents of multi-principal elements.In single principal-element alloys,dislo-cations dominate the plastic behavior.However,how dislocations interact with highly-disordered crystal lattices and/or chemical disordering/ordering will be an important factor responsible for plastic properties of HEAs.Interactions between the other crystal defects,such as twinning and stacking faults,with chemical/crystal disordering/ordering in HEAs will be important as well.1.2.1.Mechanical properties compared with other alloysFor conventional alloys that contain a single principal element,the main mechanical behavior is dictated by the dominant element.The other minor alloying elements are used to enhance some spe-cial properties.For example,in the low-carbon ferritic steels[47–59],the main mechanical properties are from the BCC Fe.Carbon,which is an interstitial solute element,is used for solid-solution strength-ened steels,and also to enhance the martensite-quenching ability which is the phase-transformation strengthening.The main properties of steels are still from Fe.For aluminum alloys[60]and titanium alloys[61],their properties are mainly related to the dominance of the elemental aluminum and tita-nium,respectively.Intermetallic compounds are usually based on two elements,e.g.,Ti–Al,Fe3Al,and Fe3Si.Interme-tallic compounds are typically ordered phases and some may have strict compositional range.The Burgers vectors of the ordered phases are too large for the dislocations to move,which is the main reason why intermetallic phases are usually brittle.However,there are many successful case studies to improve the ductility of intermetallic compound by micro-alloying,e.g.,micro-alloying of B in Ni3Al [62],and micro-alloying of Cr in Fe3Al[63,64].Amorphous metals usually contain at least three elements although binary metallic glasses are also reported,and higher GFA can be obtained with addition of more elements,e.g.,ZrTiCuNiBe(Vit-1), PdNiCuP,LaAlNiCu,and CuZrAlY alloys[65–69].Amorphous metals usually exhibit ultrahigh yield strength,because they do not contain conventional any weakening factors,such as dislocations and grain boundaries,and their yield strengths are usually three toﬁve times of their corresponding crys-talline counterpart alloys.There are several models that are proposed to explain the plastic deforma-tion of the amorphous metal,including the free volume[70],a shear-transformation-zone(STZ)[71], more recently a tension-transition zone(TTZ)[72],and the atomic-level stress[73,74].The micro-mechanisms of the plastic deformation of amorphous metals are usually by forming shear bands, which is still an active research area till today.However,the high strength of amorphous alloys can be sustained only below the glass-transition temperature(T g).At temperatures immediately above T g,the amorphous metals will transit to be viscous liquids[68]and will crystallize at temperatures above theﬁrst crystallization onset temperature.This trend may limit the high-temperature applica-tions of amorphous metals.The glass forming alloys often are chemically located close to the eutectic composition,which further facilitates the formation of the amorphous metal–matrix composite.The development of the amorphous metal–matrix composite can enhance the room-temperature plastic-ity of amorphous metals,and extend application temperatures[75–78].For HEAs,their properties can be different from any of the constituent elements.The structure types are the dominant factor for controlling the strength or hardness of HEAs[5,12,13].The BCC-structured HEAs usually have very high yield strengths and limited plasticity,while the FCC-structured HEAs have low yield strength and high plasticity.The mixture of BCC+FCC is expected to possess balanced mechanical properties,e.g.,both high strength and good ductility.Recent studies show that the microstructures of certain‘‘HEAs’’can be very complicated since they often undergo the spinodal decomposition,and ordered,and disordered phase precipitates at lower temperatures. Solution-strengthening mechanisms for HEAs would be much different from conventional alloys. HEAs usually have high melting points,and the high yield strength can usually be sustained to ultrahigh temperatures,which is shown in Fig.1.9for refractory metal HEAs.The strength of HEAs are sometimes better than those of conventional superalloys[14].Temperature dependence of NbMoTaW,VNbMoTaW,Inconel718,and Haynes2301.2.2.Underlying mechanisms for mechanical propertiesMechanical properties include the Young’s modulus,yield strength,plastic elongation,fracture toughness,and fatigue properties.For the conventional one-element principal alloys,the Young’s modulus is mainly controlled by the dominant element,e.g.,the Young’s modulus of Fe-based alloys is about200GPa,that of Ti-based alloys is approximately110GPa,and that of Al-based alloys is about 75GPa,as shown in Fig.1.8.In contrast,for HEAs,the modulus can be very different from any of the constituent elements in the alloys[79],and the moduli of HEAs are scattered in a wide range,as shown in Fig.1.8.Wang et al.[79] reported that the Young’s modulus of the CoCrFeNiCuAl0.5HEA is about24.5GPa,which is much lower than the modulus of any of the constituent elements in the alloy.It is even lower than the Young’s modulus of pure Al,about69GPa[80].On the other hand,this value needs to be veriﬁed using other methods including impulse excitation of vibration.It has been reported that the FCC-structured HEAs exhibit low strength and high plasticity[13], while the BCC-structured HEAs show high strength and low plasticity at room temperature[12].Thus, the structure types are the dominant factor for controlling the strength or hardness of HEAs.For the fracture toughness of the HEAs,there is no report up to date.1.2.3.Alloy design and preparation for HEAsIt has been veriﬁed that not all the alloys withﬁve-principal elements and with equi-atomic ratio compositions can form HEA solid solutions.Only carefully chosen compositions can form FCC and BCC solid solutions.Till today there is no report on hexagonal close-packed(HCP)-structured HEAs.One reason is probably due to the fact that a HCP structure is often the stable structure at low tempera-tures for pure elements(applicable)in the periodic table,and that it may transform to either BCC or FCC at high temperatures.Most of the HEA solid solutions are identiﬁed by trial-and-error exper-iments because there is no phase diagram on quaternary and higher systems.Hence,the trial-and er-ror approach is the main way to develop high-performance HEAs.However,some parameters have been proposed to predict the phase formation of HEAs[17,22,28]in analogy to the Hume-Rothery rule for conventional solid solution.The fundamental thermodynamic equation states:G¼HÀTSð1-2Þwhere H is the enthalpy,S is the entropy,G is the Gibbs free energy,and T is the absolute temperature. From Eq.(1-2),the TS term will become signiﬁcant at high temperatures.Hence,preparing HEAs from the liquid and gas would provide different kinds of information.These techniques may include sput-tering,laser cladding,plasma coating,and arc melting,which will be discussed in detail in the next chapter.For the atomic-level structures of HEAs,the neutron and synchrotron diffraction methods are useful to detect ordering parameters,long-range order,and short-range ordering[81].1.2.4.Theoretical simulations for HEAsFor HEAs,entropy effects are the core to their formation and properties.Some immediate questions are:(1)How can we accurately predict the total entropy of HEA phase?(2)How can we predict the phaseﬁeld of a HEA phase as a function of compositions and temperatures?(3)What are the proper modeling and experimental methods to study HEAs?To address the phase-stability issue,thermody-namic modeling is necessary as theﬁrst step to understand the fundamental of HEAs.The typical mod-eling techniques to address thermodynamics include the calculation of phase diagram(CALPHAD) modeling,ﬁrst-principle calculations,molecular-dynamics(MD)simulations,and Monte Carlo simulations.Kao et al.[82]using MD to study the structure of HEAs,and their modeling efforts can well explain the liquid-like structure of HEAs,as shown in Fig.1.10.Grosso et al.[83]studied refractory HEAs using atomistic modeling,clariﬁed the role of each element and their interactions,and concluded that4-and 5-elements alloys are possible to quantify the transition to a high-entropy regime characterized by the formation of a continuous solid solution.2.Thermodynamicsof a liquid-like atomic-packing structure using multiple elementsthird,fourth,andﬁfth shells,respectively,but the second and third shellsdifference and thus the largeﬂuctuation in occupation of different atoms.2.1.EntropyEntropy is a thermodynamic property that can be used to determine the energy available for the useful work in a thermodynamic process,such as in energy-conversion devices,engines,or machines. The following equation is the deﬁnition of entropy:dS¼D QTð2-1Þwhere S is the entropy,Q is the heatﬂow,and T is the absolute temperature.Thermodynamic entropy has the dimension of energy divided by temperature,and a unit of Joules per Kelvin(J/K)in the Inter-national System of Units.The statistical-mechanics deﬁnition of entropy was developed by Ludwig Boltzmann in the1870s [85]and by analyzing the statistical behavior of the microscopic components of the system[86].Boltz-mann’s hypothesis states that the entropy of a system is linearly related to the logarithm of the fre-quency of occurrence of a macro-state or,more precisely,the number,W,of possible micro-states corresponding to the macroscopic state of a system:Fig.2.1.Illustration of the D S mix for ternary alloy system with the composition change[17].。

单层二维材料可批量制造超薄晶体管

单层二维材料可批量制造超薄晶体管
作者：暂无
来源：《新材料产业》 2016年第9期
用仅有几个原子那么厚的薄膜做出微型、柔性的电路，一直是研究人员的梦想。

然而，把这类二维薄膜生长到需要的规模，并生产出成批可靠的电子设备一直是个难题。

现在，材料科学家们已经找出一种方法，可以在直径10c m的硅片上生长出高质量的单层二维半导体，同时还能保持小样品中所具有的出色电学性质。

他们已经用这种薄膜做出了几百个晶体管，经测试其中99%都有效。

来自康奈尔大学的JiwoongPark及其同事在Nature发表文章，称他们已经用这种方法生长出大片单层的T M D。

经过550℃高温条件下超过26h的实验，他们在直径10c m的圆形硅晶片上生长出了2种T M D：二硫化钼和二硫化钨，还能以二氧化硅薄层相隔的多层T M D材料，这可能会促进垂直结构小型、高密度三维电路的产生。

美国莱斯大学的材料科学家PulickelAjayan认为，这一技术是一项激动人心的飞跃，但要想制造出真正代表二维材料未来的商业器件，研究人员还需开发出在其他衬底、包括柔性衬底上生长薄膜的方法。

（中国半导体行业协会）。

Czochralski法在半导体级硅单晶生长中的应用

Czochralski法在半导体级硅单晶生长中的应用引言半导体技术的快速发展为现代电子产品的制造提供了坚实的基础。

而半导体材料的最基本组成部分就是硅单晶，其高纯度和晶格完整性对于制造高性能半导体器件至关重要。

为了满足对高质量硅单晶的需求，科学家们不断探索和改进各种生长方法。

在这其中，Czochralski法因其高生长质量和较大晶体尺寸的能力而成为了最常用的硅单晶生长方法之一。

本文将着重探讨Czochralski法在半导体级硅单晶生长中的应用。

一、Czochralski法的原理和特点Czochralski法，简称CZ法，是一种通过在熔融状态下来生长单晶的方法。

其原理是将高纯度的硅材料加热至熔点以上，并将立体角状的单晶硅种子缓慢地浸入熔融硅中，然后逐渐提升种子和硅熔液之间的界面。

通过拉出硅熔液和凝固加热后的单晶种子，最终获得所需尺寸和纯度的硅单晶。

Czochralski法相比其他生长方法具有如下特点：1. 高纯度：Czochralski法所需的起始硅材料纯度较高，因此容易获得高纯度的硅单晶。

这对于半导体技术来说至关重要，因为杂质的存在会严重影响半导体器件的性能。

2. 大尺寸：Czochralski法可以生长出较大尺寸的硅单晶，可达到几英寸至几十英寸的直径。

大尺寸的硅单晶对于制造大规模集成电路和其他高性能半导体器件非常重要。

3. 晶格完整性：Czochralski法生长的硅单晶具有很好的晶格完整性和结晶质量，这对于保证半导体器件的稳定性以及提高效率非常有益。

二、1. 半导体器件制造：Czochralski法生长出的硅单晶是制造各种半导体器件的重要基础材料。

例如，大规模集成电路（VLSI）在制造过程中需要使用高纯度和大尺寸的硅单晶作为衬底。

Czochralski法可以满足这些制造要求，从而保证了半导体器件的性能和稳定性。

2. 光伏行业：Czochralski法生长的硅单晶也广泛应用于光伏行业，用于制造太阳能电池。

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• Efficiency: quality of the ingots, larger and uniform grains, less defects, etc. • Yield per run: Size (weight) of the ingot, larger usable section, etc. • Cycle time: optimizing the hot zone design and process. • Energy consumption: hot zone design.
Development of Multi-crystalline Silicon Ingot Technologies
Yuepeng Wan, Dr. –Ing. CTO, LDK Solar Co. LTD. 02/23/2011, Shanghai SNEC
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• High efficiency of solar cells. • Low-cost solar grade polysilicon production technologies. • Less consumption of silicon per watt.
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