直流反应磁控溅射法制备二氧化钛薄膜的光响应_英文_

第33卷第4期 人　工　晶　体　学　报 V ol.33　N o.4　2004年8月 JOURNA L OF SY NTHETIC CRY ST A LS August,2004 Photoresponse of TiO2Thin Films Depositedby DC R eactive Magnetron SputteringZH ANG Li2wei,ZH ANG Bing2lin,Y AO Ning,F AN Zhi2qin,Y ANG Shi2e,LU Zhan2ling(K ey Laboratory of M aterial Physics,Department of Physics,Zhengzhou University,Zhengzhou450052,China)(Received9May2004)Abstract:T iO2thin films were prepared by DC reactive magnetron sputtering on IT O sur face which deposited on glass substrates.The structure of T iO2thin films was studied by Raman spectrum and the abs orption spectra.The photoresponses of T iO2thin films were investigated in virtue of photocurrent.The photoresponse time is less than100s when photocurrent reaches96%of the maximum and the photocurrent decays to dark current within200s.The sensitivity and stability of the photoresponse indicate that it is possible for T iO2thin films to be a new UV detector material.K ey w ords:DC reactive magnetron sputtering;T iO2thin films;photoresponse;photocurrentC LC number:O484 Document code:A Article I D:10002985X(2004)0420667203直流反应磁控溅射法制备二氧化钛薄膜的光响应张利伟,张兵临,姚　宁,樊志琴,杨仕娥,鲁占灵(郑州大学物理工程学院材料物理重点实验室,郑州450052)摘要:采用直流反应磁控溅射的方法在镀有IT O的导电玻璃衬底上沉积了二氧化钛薄膜,分别用拉曼光谱和吸收光谱研究了薄膜的结构,通过光电流研究了二氧化钛薄膜的紫外光响应。

在100s的时间内光电流能达到最大值的96%,当停止紫外光照射时,光电流在200s的时间内能恢复到暗电流,二氧化钛薄膜对紫外光的灵敏性和稳定的光响应表明二氧化钛薄膜有可能成为一种新的紫外光探测器材料。

关键词:直流反应磁控溅射;二氧化钛薄膜;光响应;光电流1　IntroductionT itanium dioxide,T iO2,has been known as a material with a high refractive index,high transparency in the visible and near2in frared wavelength region,high dielectric constant,very g ood wear resistance and stability.Due to these special properties,T iO2has become the subject of many investigations for applications in optical coatings[1], microelectronic devices[2]and protective layers[3].In the last decade,titanium dioxide has als o attracted a great deal of interest due to its photocatalytic behavior[4].The decom position of organic com pounds on the surface of T iO2and the reduction of the contact angle between water and the surface of T iO2under UV irradiation results in self2cleaning and anti2 fogging effects.In recent years the conductivity[5]and photocurrent[6]of T iO2films have been investigated.Anatase T iO2 bandgap is about3.2eV,when a photon whose energy hυis equal to or greater than its bandgap is abs orbed by a T iO2 particle,electron2hole pairs will be generated and transport under the electric filed,when stop UV illumination the electron2hole pairs will recombine,s o the current decreases.T iO2crystallizes in three structures:anatase,rutile and orthorhombic brookite.All the three structures can abs orb UV light.The brookite phase is stable only at very low tem peratures and hence not useful practically,s o the use of T iO2R eceived d ate:2004205209Biography:ZHANGLi2wei(19792),M ale,from Henan province,M aster candidate.E2mail:zlw@focus on rutile and anatase.Each crystalline form is convenient for different purpose.While rutile is mainly desirable for optical applications [7],in contrast to rutile ,anatase thin film has a smaller electro effective mass ,resulting in a higher m obility for the charge carriers [8],which is beneficial to further application in optoelectronic and other devices.T iO 2films can be produced by many methods ,such as s ol 2gel [9],C VD [10],reactive evaporation [11]and sputtering [12].The use of reactive magnetron sputtering provides m ore benefit in controlling the structure ,com position and properties of T iO 2thin films due to the ease of adjusting deposition conditions.Up to the present ,the report on the photocurrent of T iO 2films ,mainly focus on dye 2sensitized T iO 2thin films [13]used in s olar cells.S ome papers have reported the photocurrent of T iO 2thin films ,but the photoresponse time is longer than 400s [6],especially the photocurrent decay is very slow 2m ore than 1500s [6,14].In this paper ,T iO 2thin films were deposited on IT O substrates by DC reactive magnetron sputtering and its photoresponses under UV light were investigated.The photoresponse time is less than 100s when photocurrent reaches 96%of the maximum and the photocurrent decay is faster than their reports [6,14],what ’s m ore ,the process is s omewhat repeatable.The results give us a new in formation that it can probably be a new application -UV detector.2　ExperimentalIn our experimental situation ,IT O films were sputtered on quartz substrates by using a DC magnetron sputtering sys 2tem (CS 2300),then ,the T iO 2thin films with area of 10×10mm 2were deposited on IT O films using a high purity titani 2um target.Prior to the introduction of the sputtering gas ,the base pressure in the vacuum chamber was reduced to 1×10-3Pa by turbo pum ping.Before sputtering T iO 2thin films ,the target was pre 2sputtered in a pure arg on atm osphere for 5min in order to rem ove the surface oxide layer.The sputtering conditions were listed in T able1.Fig.1　The scheme of experiment circuitT able 1　Deposition conditions for TiO 2　thin filmsT argetT i (99.99%)Substrate tem perature200℃T otal sputtering pressure017Pa O 2/Ar1:2Base pressure<10-3Pa S puttering current0175A S puttering time 60m inThe structure of T iO 2thin films was analyzed by using Raman spectrum ,the abs orption spectra of T iO 2thin films was studied using UV 23150spectrophotometer ,the photoresponses of T iO 2thin film were measured in ambient air ,the UV light s ource was a small 4W black lam p ,the sam ple was biased at 110V ,115V and 210V.A digital am pere 2meter and a v oltage 2meter recorded the photocurrent and the v oltage respectively.Fig.1shows the scheme of the experiment circuit.3　Results and discussionFig.2shows a Raman spectrum of T iO 2thin films on IT O substrates ,the appearance of peaks at around 144,197,400,515and 640cm -1corresponding to the anatase E g m ode ,E g m ode ,B 1g m ode ,a doublet of A 1g and B 1g and E g m ode respectively ,which indicats that T iO 2thin films are anatase structure.Fig.3shows the abs orption spectrum of T iO 2thin films.It reveals that T iO 2thin films have strong abs orption when the wavelength is less than 360nm.866人工晶体学报 第33卷Fig.2　Raman spectrum of T iO 2thinfilms Fig.3　The abs orption spectrum of T iO 2thin films Fig.4is a series of photocurrent 2time curves of a sam ple measured at different bias v oltage ,110V ,115V and 210Vunder UV illumination within 2100s 1The dark current is very small ,alm ost 0μA in our experiment.A fter UV irradiationthe photocurrent can reach the maximum value 2.8μA ,within 100s it can reach 217μA (96%of the maximum ).It takesless 200s for photocurrent to drop to original dark current ,the process is s omewhat repeatable which indicated that the sam ple is sensitive to UV light and has fast photoresponse and photocurrent decay.When the bias v oltage is relatively high ,the photocurrent can rise to much higher values ,but the photoresponse time will become long.When the bias v olt 2age is lower than 015V the photocurrent is below 014μA.The sensitivity to UV light and the photoreponse have strong re 2lationship to the bias v oltage as indicated in Fig.4.At the same time ,it ’s very interesting the photocurrent decay is faster than that of other material ZnO [15]2less than 200s .As a whole ,the sensitivity to UV light ,the stability and repe 2tition of the photoresponse of T iO 2thin films are desirable to make T iO 2thin films a UV light detector.Fig.4　Photocurrent in ambient air measured at differentv oltage of 1.0V ,115V and 210V respectively4　C onclusionsIn summary ,we have deposited anatase T iO 2thin filmand studied its photoresponse.The results showed that thesensitivity to UV light ,the stability and repetition of the pho 2toresponse are g ood ,it is possible for T iO 2thin films tow ork as a new UV detector ,while the effects of the factorssuch as structure of T iO 2thin films ,the value of bias v olt 2age ,measure ambience on the sensitivity and the stability ofthe photoresponse need m ore investigations.R eferences[1]Richards B S.S ingle 2material T iO 2D ouble 2layer Antireflection C oatings[J ].Solar Energy Materials and Solar Cells ,2003,79:369.[2]Dwivedi D Dwivedi ,R Srivastava S K.The E ffect of Hydrogen 2induced Interface T raps on a T itanium Dioxide 2based Palladium G ate M OS Capacitor (Pd 2M OSC ):a C onductance S tudy[J ].Microelectronics Journal ,1998,29:445.[3]H ohenberg Schulz J ,P fl ücker H ,G ürtner F ,et al.Distribution of Sunscreens on Skin[J ].Advanced Drug Delivery Reviews ,2002,54:S157.[4]Senogles P J ,Scott J A ,Shaw G,S tratton H.Phtocatalytic Degradation of the Cyanotoxin Cylindrosperm opsin ,Using T itanium Dioxide and UV Irradiation [J ].Water Research ,2001,35:1245.[5]Chen Shin 2Fang ,W ang Ching 2Wu.E ffects of Deposition T em perature on the C onduction M echanisms and Reliability of Radio Frequency S puttered T iO 2Thin Film[J ].J.Vac.Sci.Technol.B ,2002,20:263.P 617C ontinued966第4期 ZH ANGLi 2wei et al :Photoresponse of T iO 2Thin Films Deposited by DC Reactive Magnetron S puttering 。