电子束蒸发PPT-课件
化学实验安全过滤和蒸发人教版高中化学必修一教学课件
化学实验安全过滤和蒸发课件人教版 高中化 学必修 一
物质提纯的原则
无新 不减 易分 从简 无害
一般将杂质转为沉淀、气体或水， 是指易于主要物质分离
化学实验安全过滤和蒸发课件人教版 高中化 学必修 一
物质提纯的原则
无新 不减 易分 从简 无害
化学实验安全过滤和蒸发课件人教版 高中化 学必修 一
1.1.2 化学实验的基本方法 混合物的提纯与分离
化学实验安全过滤和蒸发课件人教版 高中化 学必修 一
思考与交流
1.淘金者是利用什么性质和方法将金子从沙子分出
来的？ 用水洗。金的密度很大，所以可用水冲洗的方法
从沙里提取密度很大的金。在用水冲洗沙时，密度 小的泥土、细沙等物质被水冲去，可提取含量极少 的金。
药品：粗盐、水
化学实验安全过滤和蒸发课件人教版 高中化 学必修 一
化学实验安全过滤和蒸发课件人教版 高中化 学必修 一
实验1-1 粗盐的提纯
实验仪器及药品
实验步骤及现象 课本P6操作步骤
化学实验安全过滤和蒸发课件人教版 高中化 学必修 一
化学实验安全过滤和蒸发课件人教版 高中化 学必修 一
四实、验过1滤-1:和粗蒸盐发的的提应纯 用
化学实验安全过滤和蒸发课件人教版 高中化 学必修 一
蒸发操作及注意事项
蒸发概念 仪器用品 装置图 注意事项
分离溶于溶剂中的固体物质的一 种方法
化学实验安全过滤和蒸发课件人教版 高中化 学必修 一
化学实验安全过滤和蒸发课件人教版 高中化 学必修 一
蒸发操作及注意事项
蒸发概念 仪器用品 装置图 注意事项
BaSO4 ↓
调节PH值至中性
BaCl2
稍
过
《真空蒸发》PPT课件
❖ 其它成膜技术：液相外延(LPE)，电沉积，溶胶 凝胶(sol-gel)，自组装，spin-coating，化学 浴沉积(CBD)等。
❖ 新的薄膜制备技术： ➢ 以蒸发沉积为基础发展出了电子束蒸发沉积、分子束
directional, cosnq,
~ 2 J/脉冲， 脉冲频率 ~ 30 Hz ArF (193 nm) KrF (248 nm) XeCl (308 nm)
窗口材料：MgF2, sapphire, CaF2, UV-grade quartz
光被材料吸收
T
热传导：
温度分布：
x
蒸发速率：
优点： 瞬时加热，具有闪烁蒸发的特点；能保 持源料组分；污染少；难熔金属；易实 现同时或顺序多源蒸发。 缺点： 昂贵；膜厚不易控制(单个脉冲就可沉积 数百纳米)；容易有粒子飞溅；蒸发量少； 不适合工业生产；
到基体表面的镀膜方法；
➢ 通常是固体或熔融源； ➢ 在气相或衬底表面没有化学反应； ➢ 代表性技术：蒸发镀膜、溅射镀膜； ➢ 技术特点：真空度高、沉积温度低、设备相对
比较简单。薄膜质量差，可控度小、表面容易 不均匀。
❖ 化学气相沉积(CVD) ➢ 化学气相沉积: 沉积过程中发生化学反应，薄膜
与原料的化合状态不一样。 ➢ 代表性技术：低压CVD(LPCVD), 常压CVD APCVD,
Oblique and edge views of a tetragonal square spiral structure
Scott R. Kennedy, et al
Nano Letters Between the 4th and 5th bands, very robust to disorder. 15%,
真空蒸发(蒸发镀膜)PPT幻灯片课件
在100℃时，水的饱和蒸气压增大到101324.72Pa
8
第一节 真空蒸发原理
蒸发温度
规定物质在饱和蒸气压为10-2Torr时的温度 饱和蒸气压与温度的关系曲线对于薄膜制作技术有重要 意义，它可以帮助我们合理选择蒸发材料和确定蒸发条件。9
第一节 真空蒸发原理
3. 蒸发速率
根据气体分子运动论，在气体压力为P时，单位时间 内碰撞单位面积器壁上的分子数量，即碰撞分子流量（通
30
第二节 蒸发源的蒸发特性及膜厚分布
★ 点蒸发源
能够从各个方向 蒸发等量材料的微小 球状蒸发源称为点蒸 发源（点源）。
dm m d 4
m
4Байду номын сангаас
cos
r2
dS2
dm t dS2
dS1 dS2 cos
dS1 r 2 d
d
dS2 cos
r2
18
电子束加热原理
• 可聚焦的电子束，能局部加温元素源，因不加热其它部 分而避免污染 • 高能量电子束能使高熔点元素达到足够高温以产生适量 的蒸气压
电子的动能和电功率：
m 9.11028 g
1 m2 e U
2 e 1.61019C
5.93105 U (m/s)
Q 0.24Wt
19
电子束蒸发源的优点：
• 电子束的束流密度高，能获得远比电阻加热源更大的能 量密度。
• 被蒸发材料置于水冷坩埚内，避免了容器材料的蒸发， 以及容器材料与蒸发材料的反应，提高了薄膜的纯度。
• 热量直接加到蒸镀材料表面，热效率高，热传导和热辐 射损失小。
电子束蒸发源的缺点：
电子束蒸发.
直枪是一种轴对称的直线加速枪，从加热灯丝发射出的电子束，经阳极加
速后在磁场作用下聚焦，而后轰击坩埚中的材料使之熔化和蒸发。其中， x-y偏转线圈的作用是使聚焦电子束能够在一小范围内移动，从而使聚焦
凹箔由钨、铊或钼的薄片制成，厚度一般在 0.005-0.015 英寸。当 只有少量的蒸发材料时最适合于使用这一蒸发源装置。在真空中加热 后，钨、铊或钼都会变脆，特别是当它们与蒸发材料发生合金化时更 是如此。
电阻加热蒸发的主要缺点是：
（1）支撑坩埚及材料与蒸发物反应。 （2）难以获得足够高的温度使介电材料如Al2O3、 Ta2O5、TiO2等蒸发。 （3）蒸发率低。 （4）加热时合金或化合物会分解。
斑位置得以调节。
优点：使用方便；功率变化范 围广（几百瓦到几百千瓦）； 易于调节
缺点：设备体积大、结构复杂、成 本高；蒸发材料会污染枪体结构， 同时灯丝上逸出的钠离子会引起薄 膜的沾污。
e形枪是电子束偏转270°的电子枪，因电子轨迹呈“e”形而得名。 从灯丝发射出的电子束，受到数千伏偏置电压的加速，并经横置的 磁场偏转270°后再轰击坩埚中的蒸发材料使之熔化和蒸发。
由于与盛装待蒸发材料的坩埚相接触的蒸发材料在 整个蒸发沉积过程保持固体状态不变，这样就使待 蒸发材料与坩埚发生反应的可能性减少到最低。直 接采用电子束加热使水冷坩埚中的材料蒸发是电子 束蒸发中常用的方法。对于活性材料、特别是活性 难熔材料的蒸发，坩埚的水冷是必要的。通过水冷 ，可以避免蒸发材料与坩埚壁的反应，由此即可制 备高纯度的薄膜。
在电子束蒸发系统中，产生电子束的装置成为电子枪， 根据电子聚焦方式的不同，电子枪可分为环形枪、直枪 和e形枪等。
电子束蒸发PPT-PPT课件
可蒸发高熔点材料 成膜质量较好 缺点：要求高真空 设备成本高
电子束蒸发特点： 优点： 直接加热，效率高 能量密度大，蒸发高熔点材料 冷坩埚，避免反应和蒸发 ， 提高薄膜纯度 缺点：装置复杂 残余气体和部分蒸气电离 对薄膜性能产生影响
高频感应蒸发
工作原理：线圈在高频磁场作用下因产生强大的涡流损失和 磁滞损失而升温，使材料受热蒸发。
真空蒸发技术
许爱燕
21105004
真空蒸发镀膜法：将固体材料置于高真空环境中加热，使之升华或蒸发 并沉积在特定衬底上以获得薄膜的工艺方法
技术分类：依据蒸发源的不同
电阻热蒸发
真 空 蒸 发 技 术
电子束蒸发
高频感应蒸发 激光束蒸发
反应蒸发
电阻热蒸发
热蒸发：蒸发材料在真空室中被加热，其原子 或分子从表面逸出的现象
激光蒸发装置（叶志镇 2019）
反应蒸发
工作原理：在一定反应气氛中蒸发金属或低价化合物，使之在淀积过程中 发生化学反应而生成所需的高价化合物薄膜
反应蒸发法是真空镀 膜方法的一种改进
特点：
产生等离子体， 使蒸发材料和反 应气体电离活化， 提高反应效率
反应蒸发装置图（叶志镇 2019）
谢谢大家
加热方式：电阻加热
电阻材料：难熔金属 优点：构造简单、造价便宜、使用可靠
缺点：加热所达最高温度有限、蒸发速率较低、蒸发面积小、 不适用于高纯和高熔点物质的蒸发
电子束蒸发：将蒸发材料置于水冷坩埚中，利用电子束直接加热使蒸 发材料汽化并在衬底上凝结形成薄膜
蒸度高熔点薄膜和高纯薄膜的一种主要加热方法
电子枪由电子束聚焦方式的不同分类： 直式电子枪 环枪（电偏转） e形枪（磁偏转）
本文对电子束蒸发系统进行了详细的...
摘要本文对电子束蒸发系统进行了详细的研究，并对影响电子束蒸发的五个主要因素包括铝源、坩埚、烘烤温度、高压供给和真空进行了全面的分析，在理论分析的基础上，分别对其作了关键性的对比实验，并对实验数据应用MSO EXCEL 进行了分析与绘图，从直观的角度分析对比，得出了最优方案。
本文采用递进优化的实验方法，即先对其中之一的因素作对比实验，得出较好的条件后将其用于第二个因素实验的先决条件，依此类推，从而优化设备硬件及工艺条件。
通过研究与实验，得出了适合本车间最优的设备硬件与工艺条件：即采用进口铝源作为蒸发源；用Telemark 258 Electron Bean Gun 258型的坩埚作为蒸发源载体；烘烤温度满足在200℃左右；高压方面应用-10KV的高压供给，在达到这四个条件后，最重要的条件真空度再达到7.0×10-7TORR以上时，铝层质量包括致密性（腐蚀速率）、一致性（方块电阻）达到最好效果。
关键词：电子束，铝源，坩埚，烘烤温度，高压IABSTRACTI made a detailed study about electron beam evaporation system in this graduation thesis, and made a comprehensive analysis on impact of electron beam evaporation and the five major factors include aluminum source crucible, baking temperature, high voltage supply and vacuum. Based on analyzing the basic theories, respectively to make pivotal contrastive experiments. Application of the experimental data analysis and graphics MSO EXCEL obtained after drawing from the visual point of view of comparing the optimal plan.The result of the experimental method used to optimize. Firstly I made experiments on one of the factor, that make comparative experiments had good conditions for the second factor will be the prerequisite for the experiment, and so on, thus obtained for the workshop the best equipment hardware and process conditions. And the conclusion is that we must use imported aluminum source as evaporation source; with Telemark 258 Electron Bean Gun 258-type evaporation source crucible as a carrier; baking℃-10KV high voltage application of the temperature is about to meet in the 200 ;high-voltage supply, in achieving these four conditions, the most important conditions for the vacuum and then to 7.0 × 10-7TORR above, the aluminum layer of quality, including density (corrosion time), consistency (sheet resistance) to achieve the best results.Keywords：electron beam evaporation， aluminum source，crucible, baking temperature, high voltage supplyII目录第一章引言 (1)1.1 电子束蒸发的发展 (1)1.2 电子束蒸铝的分类 (1)1.2.1 电子束蒸发源蒸镀法 (1)1.2.2 高频感应蒸发源蒸镀法 (1)1.2.3 电阻蒸发源蒸镀法 (1)1.2.4 激光束蒸发源蒸镀法 (2)1.2.5 磁控溅射在表面改性技术中的应用 (2)1.2.6 等离子增强磁控溅射沉积技术（PMD） (2)1.2.7 反应磁控溅射技术 (3)1.2.8 离子镀 (3)1.3 本文所做的工作 (3)第二章电子束蒸铝的影响因素 (4)2.1设备总体概括 (4)2.2铝源 (5)2.3坩锅 (5)2.4蒸发速率 (5)2.5烘烤 (6)2.6高压电子束的供给系统 (6)2.7真空 (6)2.7.1真空的概念 (6)2.7.2真空的分类 (6)2.7.3真空在电子束蒸发中的重要性 (7)第三章研究对象的研究及规格统一 (8)III3.1 铝源的研究与规格比较 (8)3.2 坩埚的研究与规格确定 (9)3.3蒸发速率的研究 (12)3.4烘烤温度方面 (14)3.5 高压供给系统的研究 (15)3.5.1环形枪 (15)3.5.2偏转式电子枪 (17)3.6真空 (18)3.6.1 机械泵的研究 (19)3.6.2 罗茨泵的研究 (21)3.6.3 低温泵的研究 (23)3.6.4 各台设备真空值的校准与统一 (24)第四章单台设备进行的工艺实验 (26)4.1设备的确定 (26)4.2 工艺参数与实验方法的确定 (26)4.3实验及数据 (28)4.3.1 第一实验：铝源选用 (28)4.3.2 第二实验：坩埚实验 (31)4.3.3 烘烤实验 (35)4.3.4 电压电流实验 (43)4.3.5 真空实验 (47)第五章结论 (56)致谢 (57)参考文献 (58)IV第一章引言1.1 电子束蒸发的发展电子束蒸发镀膜技术最初起源于上个世纪30年代，直到70年代后期才得到了较大发展，此技术在整个工业生产中具有十分重要的地位，国内外无论是半导体制造厂抑或是精密光学厂商在此领域都有所研究，广泛应用在耐酸、耐蚀、耐热、表面硬化、装饰、润滑、光电通讯、电子集成、能源等领域。
E型电子束蒸发器
E型电子束蒸发器（JYK-电子枪）目录E型电子束蒸发源一.概述本蒸发源系坩埚由电机直接驱动、电子束偏转角为270º、用于蒸镀各种金属和非金属材料的磁偏转式E型电子束蒸发装置。
二、主要技术参数1、电子束偏转角 270º2、阳极电压 10KV3、阴极加热电源 AC 3V+3V，60A可调4、束流直冷坩埚0～1A5、坩埚容量（标准型）6、磁场电源X偏转电流±2A可调扫描频率 10～250HZY偏转电流±2A可调扫描频率 10～250HZ7、启动真空度 6.7×10-3Pa8、坩埚定位(四孔坩埚) 电控自动或手动点控9、坩埚冷却水进水温度≤25℃进水压力≥0.2MPa水流量≥8L/min10、电子枪体接地电阻≤4Ω三.结构说明1. 电子枪电子枪是产生电子束的部件,由直线状螺旋钨阴极、栅极和阳极组成。
加速电压采用负高压，阴极和栅极处于相同的负电位，阳极接地电位。
阴极由交流供电加热，使之发射电子，电子受栅极电位的影响，在阳极电压加速下形成会聚的电子束。
在X方向磁场（左为S极、右为N极）的作用下，电子束得到进一步聚焦并偏转270º射入装有被镀膜料的坩埚中，其动能变成热能使材料蒸发沉积于基片上，达到所需膜层的要求。
2．X、Y偏转和扫描X、Y偏转线圈采用铝金结构。
改变X线圈电流大小，电子束可作前后移动；改变Y线圈电流大小，电子束可作左右移动。
通过调整X、Y线圈电流大小，可使束斑射于膜料的所需位置上。
通常使Y线圈偏转电流为零，调整X线圈电流，使束斑居于坩埚中心位置。
若再给X、Y线圈加上交变电流，则电子束可在膜料上作不同幅度（圆或其它形状）和频率的自动扫描。
3．冷却水正常的冷却水是保证不损坏坩埚及密封胶圈等部件的关键，欲达到技术指标中的供水要求，请用户给电子束蒸发源单独供水，而不要由主机的供水管供水（参见图1）；并在工作中随时监视水流情况。
未达到供水要求，严禁使电子枪工作。
电子薄膜实验PPT课件
1. 气相成底膜 • 工艺目的：增加光刻胶与硅片的粘附性。
电子薄膜实验
• 工艺方法： 硅片放在成底膜真空腔中的热板上，热板温度控
制在200 ℃ ～250℃，用N2携带六甲基二硅胺 烷（HMDS）进入真空腔，处理时间60秒。这 样在硅片上形成了底膜。 HMDS是液态具有很高的蒸气压，能使光刻胶 与硅片很好地粘附。
主要参数：时间、温度
典型的软烘条件：在热板上100度烘60S
电子薄膜实验
4、对准和曝光 • 工艺目的： 将掩膜板上的图形通过镜头由紫外线
传递到硅片表面光刻胶膜上, 形成光敏感物质在空 间的精确分布，最终达到图形精确转移的目的。
电子薄膜实验
4、对准曝光 系统示意图
电子薄膜实验
电子薄膜实验
电子薄膜实验
URE-2000/35光刻机
中国科学院光电技术研究所
• 紫外接近，接触式光刻 • 曝光面积：100mm×100mm； • 分辨力：1μm（胶厚2μm 的正胶）； • 掩模尺寸：2.5inch、3 inch、4 inch、5 inch； • 样片尺寸：Φ15mm - Φ100 mm； • 样片厚度：0.1mm - 6mm； • 曝光波长：365nm
电子薄膜实验
• 电子束蒸发系统
电子束蒸发系统 电子薄膜实验
DZS-500型电子束蒸发镀膜机 • 中科院沈阳科学仪器研制中心 电子薄膜实验
• 电子束蒸发系统的组成： 1. 高压电源系统 2. 真空系统 3. 电子加速聚焦偏转系统 4. 工艺腔 5. 水冷坩锅系统（通常为带旋转的四坩锅） 6. 载片架
化温度450～500℃） 4. 易于沉积成膜 5. 易于光刻和刻蚀形成微图形
电子薄膜实验
6. 抗腐蚀性能好，因为铝表面总是有一层抗腐蚀 性好的氧化层（Al2O3） 7. 铝的成本低
电子束蒸发原理(共11张PPT)
3.溅射技术
• 磁控溅射的工作原理是指电子在电场E 的作用下，在飞向基片过程中与氩原子发 在溅射粒子中，中性的靶原子或分子沉积在基片上形成薄膜 。
(E-Gun Evaporation) 以电场和磁场的控制，我们便能控制电子束扫描的区域及面积的大小。
电子束蒸发原理
蒸镀机照片
一.金属蒸镀的分类
• 一.热蒸镀 • 二.电子束蒸镀 • 三,溅射蒸镀
1.热蒸镀
• Thermal Evaporation 就是在高真空下，将所要蒸镀的材料，
利用电阻加热到达熔化温度，使其蒸发， 达到并附着在基底表面的一种技术。
2.电子束蒸镀
• (E-Gun Evaporation) 就是在高真空下，将所要蒸镀的材料，
生碰撞，使其电离产生出Ar和新的电子； 新电子飞向基片，Ar 在电场作用下加速飞向阴极靶，并以高能量轰击靶表面，使靶材发生溅射。
以电场和磁场的控制，我们便能控制电子束扫描的区域及面积的大小。 (E-Gun Evaporation)
新电子飞向基片，Ar 在电场作用下加速飞 就是在高真空下，将所要蒸镀的材料，利用电阻加热到达熔化温度，使其蒸发，达到并附着在基底表面的一种技术。
• 以电场和磁场的控制，我们便能控制电子 束扫描的区域及面积的大小。
E-GUN的结构示意图
可聚焦的电子束，能局部加温元素源，因不加热其它部分而避免污染。 (E-Gun Evaporation) (E-Gun Evaporation) 以电场和磁场的控制，我们便能控制电子束扫描的区域及面积的大小。 新电子飞向基片，Ar 在电场作用下加速飞向阴极靶，并以高能量轰击靶表面，使靶材发生溅射。 高能量电子束能使高熔点元素达到足够高温以产生适量的蒸气压。 (E-Gun Evaporation) 可聚焦的电子束，能局部加温元素源，因不加热其它部分而避免污染。 磁控溅射的工作原理是指电子在电场E的作用下，在飞向基片过程中与氩原子发生碰撞，使其电离产生出Ar和新的电子； 以电场和磁场的控制，我们便能控制电子束扫描的区域及面积的大小。 高能量电子束能使高熔点元素达到足够高温以产生适量的蒸气压。 高能量电子束能使高熔点元素达到足够高温以产生适量的蒸气压。 高能量电子束能使高熔点元素达到足够高温以产生适量的蒸气压。 在溅射粒子中，中性的靶原子或分子沉积在基片上形成薄膜 。 以电场和磁场的控制，我们便能控制电子束扫描的区域及面积的大小。 新电子飞向基片，Ar 在电场作用下加速飞向阴极靶，并以高能量轰击靶表面，使靶材发生溅射。 新电子飞向基片，Ar 在电场作用下加速飞向阴极靶，并以高子束蒸镀
电子束蒸镀
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根据Bonguer-Lambert定律,ITO薄膜对光的吸收遵循: τ(λ)=10-αl
(其中,τ(λ)为透过率,α为介质的吸收系数,l为光通过 薄膜的距离)
黑色InO、SnO、Sn3O4和晶界的存在使吸收系数α变 大 从而导致ITO薄膜的透过率下降. 所以尽可能生成In2O3和SnO2,而减少InO、SnO、 Sn3O4 的生成是制备具有优异光电性能的ITO薄膜的关键。
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体 膨胀吸热的原理产生极低的温度，然后依据低温抽气的作用以达 到抽真Insp空ur gr的oup效2果020/。3/17
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图六 冷泵示意图
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图七 压缩机工作原理示意图
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CRTM9000程序的设定
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生产过程控制
通过以上的分析，蒸镀ITO需要控制好的就是In、Sn 的氧化问题，也就是蒸镀过程中氧流量、温度和蒸镀速 率的问题也包括蒸发腔室的洁净。所以控制好这些因素 就能实现ITO的稳定生产。
氧气流量：通过质量流量控制计控制。现在蒸镀条件 是13sccm。通氧量的多少直接影响ITO的参数，但是它
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图一 E型电子枪的结构图
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第六节电子束完整版PPT资料
工作特点
• ③E靶环位于D靶环前方，用于调整 电子束形状和扫描轨迹，但不产生图像 数据。
3.扫描体位
(2)心脏长轴位 :检查床面不倾斜，检查 床长轴反时针旋转25°，使扫描层面与心 脏长轴平行，显示心脏长轴位影像。扫描 范围应覆盖整个心脏。心脏长轴位用于观 察二尖瓣、左室根部、主动脉流出道和心 尖部病变，是心脏多层电影检查的常用扫 描体位(图3-12)。
• 4Байду номын сангаас特点
• EBCT的最大特点是时间分辨力高。时间分辨力
过高真空偏移管，聚焦线圈使电子束聚 邻的两个靶环扫描产生的图像有4mm的组织间隔。
8s内达629mm，可扫描40层；
焦成毫米级的小焦点，而偏转线圈的磁 一、电子束CT的特点
(2)心脏长轴位 :检查床面不倾斜，检查床长轴反时针旋转25°，使扫描层面与心脏长轴平行，显示心脏长轴位影像。 2s内可扫描140层，最大扫描范围可覆盖胸腹主动脉及其主要分支。
场变化使得聚焦电子束旋转轰击四个弧 循环时间是血液从一个标记点流到另一个标记点的时间，测定的方法有两种。
MSM)是采用多靶扫描。
形静止钨靶环 (依次为A、B、C、D环)中 观察右心，扫描与注药同时或稍延迟2s。
(2)动态触发:由呼吸运动控制。 血流扫描如果观察左心，扫描起始时间约为1/2循环时间；
的一个，产生旋转的X线。 根据临床的诊断要求和电子束CT的扫描方式不同，有3种对比剂的注射方法。
• 3.扫描体位
电子束和离子束加工PPT课件
格较贵，故在生产中受到一定程度的限制
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四、电子束加工的应用
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1、电子束打孔 能加工各种孔，包括异形孔、斜孔、锥孔
和弯孔。
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2、电子束切割 可对各种材料进行切割，切口宽度仅有
3~6µm 利用电子束再配合工件的相对运动，可加
工所需要的曲面
1
控制电子束能量密度的大小和能量注入时 间，就可以达到不同的加工目的
只使材料局部加热就可进行电子束热处理 使材料局部熔化可以进行电子束焊接 提高电子束能量密度，使材料熔化和气化，
就可以进行打孔、切割等加工 利用较低能量密度的电子束轰击高分子材
料时产生化学变化，可进行电子束光刻加 工
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二、加工装置 电子束加工装置主要由以下几部分组成 1、电子枪——获得电子束的装置 电子发射阴极——用钨或钽制成，在加热
第一节 电子束加工
一、电子束加工的基本原理 在真空条件下，利用电子枪中
产生的电子经加速、聚焦后能量 密度为106~109w/cm3的极细束流 高速冲击到工件表面上极小的部 位，并在几分之一微秒时间内， 其能量大部分转换成热能，使工 件被冲击部位的材料达到几千摄 氏度，致使材料局部熔化或蒸发， 来去除材料
状态下发射电子 控制栅极——既控制电子束的强弱，又有
初步的聚焦作用 加速阳极——通常接地，由于阴极为很高
的负压，所以能驱使电子加速
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2、真空系统 保证电子加工时所需要的真空度。
3、控制系统和电源 控制系统包括束流聚焦控制、束流位置控制、束 流强度控制以及工作台位移控制
1）束流聚焦控制：提高电子束的能量密度，它决定 加工点的孔径或缝宽
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第5讲 蒸发法 PPT
何谓物理气相沉积？
何谓物理气相沉积（physical vapor deposition, PVD)：利用 某种物理过程，如物质的热蒸发或在受到粒子轰击时物质 表面原子的溅射等现象，实现物质原子从源物质到薄膜的 可控转移的过程。
物理气相沉积法制备薄膜的特点： 1、需要使用固态的或者熔融态的物质作为沉积过程的源物质； 2、源物质经过物理过程而进入环境； 3、需要相对较低的气体压力环境； 4、在气相中及在衬底表面并不发生化学反应。 物理气相沉积的三个阶段： 1、从源材料中发射出粒子； 2、粒子输运到基片； 3、粒子在基片上凝结、成核、长大、成膜。
dAs
r2
式中，Ms为衬底面积As上沉积的物质的质量；Me为蒸发出来的物质总量；θ 是衬底
表面法线与空间角方向间的偏离角度；r是蒸发源与衬底之间的距离；Φ是面蒸发
源平面法线与空间角方向间的偏离角度。
显然，薄膜沉积速率将与距离r的平方成反比，并与θ、 Φ有关。
薄膜沉积的厚度均匀性是一个经常需要考虑的问题。需要同时沉积的薄膜的面积 越大，则沉积均匀性的问题越突出。
（2）加热装置所用电阻材料要求：
1）使用温度高，即熔点要高，必须高于蒸发材料的蒸发温度；
2）高温下蒸气压低。这主要是为防止或减少高温下蒸发源材料会成为杂质 进入蒸镀膜层中。只有蒸发源材料的饱和蒸气压足够低。才能保证蒸发时具有最 小的自蒸发量，而不致于产生影响真空度和污染膜层质量的蒸气；
3）在化学性能稳定，高温下不应与蒸发材料发生化学反应；
4）无放气现象或其它污染，并具有合适的电阻率；
5）在选择加热装置所用电阻材料时，还必须考虑蒸发材料与电阻材料的 “湿润性”问题。在湿润的情况下，由于材料的蒸发是从大的表面上发生的且比 较稳定．所以可认为是面蒸发源的蒸发；在湿润小的时候，一般可认为是点蒸发 源的蒸发。另外，如果容易发生湿润，蒸发材料与电阻材料十分亲合。因而蒸发 状态稳定；如果是艰以湿润的，在采用丝状挥发源时，蒸发材料就容易从电阻材 料上掉下来。
在微生物燃料中使用电子束蒸发方法沉积高效廉价的铂
Effective and Low-Cost Platinum Electrodes for Microbial Fuel Cells Deposited by Electron Beam Evaporation Ho Il Park,†Usman Mushtaq,†David Perello,†Innam Lee,†Sung Kwon Cho,‡Alexander Star,§and Minhee Yun*,†Department of Electrical and Computer Engineering,Uni V ersity of Pittsburgh,Pittsburgh,Pennsyl V ania, Department of Mechanical Engineering and Materials Science,Uni V ersity of Pittsburgh,Pittsburgh, Pennsyl V ania,and Department of Chemistry,Uni V ersity of Pittsburgh,Pittsburgh,Pennsyl V ania Recei V ed March28,2007.Re V ised Manuscript Recei V ed June7,2007A microbial fuel cell(MFC)is a device that converts chemical energy to electrical energy through the catalytic reaction of microorganisms.In this paper,electricity generation was investigated in microbial fuel cells using e-beam deposited Pt electrodes to improve efficiency and minimize Pt loading.We deposited Pt on carbon paper electrodes using an e-beam evaporator and imaged microscopic structures of the Pt deposited electrodes using scanning electron microscopy and atomic force microscopy.Although the e-beam electrode had the least thick Pt layer(1000Å)among many tested electrode types(Pt-black)1500Åand commercial electrode)2500Å),it showed excellent coverage and Pt uniformity,resulting in minimal loading of Pt.In MFC testing,the e-beam Pt electrode installed only on the anode(carbon paper electrode on the cathode) produced the highest peak value of0.42A/m2in the current density,which was about2times higher than when the Pt-black anode electrode or E-Tek commercial Pt anode electrode was used.After45h of microbial fuel cell running with the Pt electrode on the anode,the carbon electrode on the cathode was also replaced with an e-beam electrode.This replacement generated an immediate rise in current density,reaching a second peak of0.50A/m2.Considering the mass-specific current density,which represents the current density per unit Pt thickness,the e-beam electrode was the most effective with minimal Pt loading.The mass-specific current density for the e-beam electrodes was2.5times higher than that for the E-Tek commercial electrodes. These promising results suggest the high potential of e-beam-deposited Pt electrodes in improving microbial fuel cell efficiency with minimal Pt loading.IntroductionA microbial fuel cell(MFC)is a device that converts chemical energy to electrical energy through the catalytic reaction of microorganisms.1Typical MFCs mainly consist of anode and cathode compartments separated by a cation-specific mem-brane.2Fuel typically for which wastewater or food processing wastewater is used is oxidized by microorganisms that produce electrons and protons in the anode compartment.3The electrons flow via a wire to the cathode compartment while the protons pass through the separating membrane,eventually reaching the cathode compartment.Both electrons and protons are eventually consumed in the cathode compartment,reducing oxygen to form water.4,5In this process,electric power can be extracted by applying electric loads to the wire.Currently,MFCs seem to promise an alternative energy source.As nonrenewable energy sources such as coal and petroleum become limited,the use of renewable sources such as wastewater and food processing wastewater becomes more demanding.This is one of the main reasons to draw more attention to MFCs.Of equal importance,after the oxidation/ reduction reactions in MFCs,the used wastewater or food processing wastewater becomes more sanitary and thus envi-ronmentally friendly.Therefore,MFCs can be used even in space cabins and habitats to purify astronauts’excretions and possibly recycle them into clean water,6as well as to generate energy.However,MFCs typically have shown lower levels of efficiency in power generation compared to other types of fuel cells,7which has critically restricted their practical use for an energy source.To improve their efficiency,numerous ap-proaches have been made.Some groups have modified electrode materials using metal,surfactants,and organic materials.8-10*Corresponding author.Phone:(412)648-8989.Fax:(412)648-8003. E-mail:yunmh@.†Department of Electrical and Computer Engineering.‡Department of Mechanical Engineering and Materials Science.§Department of Chemistry.(1)Akiba,T.;Bennetto,H.P.;Stirling,J.L.;Tanaka,K.Electricity generation from alkalotrophic organisms.Biotechnol.Lett.1985,9,611-616.(2)Gil,G.C.;Chang,I.S.;Kim,B.H.;Kim,M.;Jang,J.K.;Park,H. S.;Kim,H.J.Operational parameters affecting the performance of a mediator-less microbial fuel cell.Biosens.Bioelectron.2003,18,327-334.(3)Oh,S.;Logan,B.E.Hydrogen and electricity production from a food processing wastewater using fermentation and microbial fuel cell technologies.Water Res.2005,39,4673-4682.(4)Allen,R.M.;Bennetto,H.P.Microbial fuel cell.Appl.Biochem. Biotechnol.1993,39/40,24-40.(5)Chang,I.S.;Moon,H.;Bretschger,O.;Jang,J.K.;Park,H.I.; Nealson,K.H.;Kim,B.H.Electrochemically active bacteria(EAB)and mediator-less microbial fuel cells.J.Microbiol.Biotechnol.2006,16,163-177.(6)Lovley,D.R.Microbial energizers:Fuel cells that keep on going. Microbes tat produce electricity by oxidizing organic compounds in biomass may someday power useful electronic devices.Microbes2006,1,323-329.(7)Cheng,S.;Liu,H.;Logan,B.E.Power densities using different cathode catalysts(Pt and CoTMPP)and polymer binder(Nafion and PTFE) in single chamber microbial fuel cells.En V iron.Sci.Technol.2006,40, 364-369.(8)Chen,P.;Fryling,M.A.;McCreery,R.L.Electron transfer kinetics at modified carbon electrode surface:The role of specific surface sites. Anal.Chem.1995,67,3115-3122.(9)DuVall,S.H.;McCreey,R.L.Control of catchol and hydroquinone electron-transfer kinetics on native and modified glassy carbon electrodes. Anal.Chem.1999,71,4594-4602.2984Energy&Fuels2007,21,2984-299010.1021/ef070160x CCC:$37.00©2007American Chemical SocietyPublished on Web08/03/2007Other groups have used different mediators such as thionine,11 viologens,1and methylene blue.12Recently,ferricyanide13,14and peroxide15have been used to increase the rate of the oxygen reduction reaction.More recently,membraneless MFCs15,16have been devised,and a biofilm has been employed on cathode electrodes.18Even though the above approaches have made improvements to some degree,it is known that the most attractive and effective is to employ Pt as an electrocatalyst on the electrodes.Pt,a noble metal,is known as one of the most widely used and efficient electrocatalysts for fuel cells.19,20It is often utilized in Pt-metal alloy forms such as Pt/Ni,21Pt/ Cr,22and Pt/Ru23,24or combined with other binders such as polyaniline,25nafion,26poly tetrafluoroethylene(PTFE)7and cobalt tetramethylpenyl-porphyrin(CoTMPP).7The use of Pt as an electrocatalyst results in one major drawback.Pt is extremely expensive,causing significant cost problems in fuel cell manufacturing and production.20Therefore, recent research activities have been focused on minimizing the loading amount of Pt27as well as other precious metals,20and on enhancing their catalytic activities.In H2/air-fed polymer electrolyte membrane fuel cells,27highly dispersed Pt-black and Pt nanoparticles have been grown on carbon(Pt/C)in the membrane/electrode assembly using an electrochemical deposi-tion method.This has resulted in a reduction of Pt loading down to3000∼4000Åin thickness.Similarly,another study28used Pt layers of250∼2000Å.In addition,various electrode configurations with electrochemically deposited Pt layers were implemented in relation to microbial fuel cells:for example, 1750∼2500ÅPt on electrodes(Mahlon et al.29),2500ÅPt on electrodes in a nafion solution(Liu et al.10),1400ÅPt on graphite electrodes in a nafion solution(Pham et al.26),1750 and2500ÅPt by way of using Pt/Ru of1:1molar ratio(Logan et al.17),and500∼10000ÅPt with PTFE or CoTMPP(Cheng et al.7).These configurations were often incorporated with physical dispersity generated by air spray guns.Among the aforementioned cases,Cheng et al.7reported the lowest Pt loading on cathode electrodes(500Å).In this case,however, the thin Pt layers suffered from nonuniformity and poor activity.7,30To obviate these problems,more controllable deposition methods with better uniformity are highly desired.An e-beam evaporation deposition method,which is commonly used in micro-and nanofabrication,is known to produce reproducible and reliable thin layers of Pt as well as other materials whose thicknesses range from tens of angstroms to thousands of micrometers.Furthermore,this method is highly controllable and cost-effective,providing improved structural properties in deposited layers.31In this paper,we apply the e-beam evaporation method to deposit Pt nano layers uniformly on microbial fuel cell electrodes,to apply the e-beam-deposited Pt electrodes to a microbial fuel cell,and to examine their performance in terms of current density and power generation.Finally,the test results of the e-beam electrodes are compared with those of electro-chemically deposited Pt electrodes,commercial Pt electrodes, and carbon paper electrodes.Preparation of the ExperimentAnaerobic Sludge.Anaerobic sludge was collected from the wastewater treatment plant of the Franklin Township Municipal Sanitation Authority in Pittsburgh.The anaerobic sludge was inoculated using artificial wastewater,which contained50mM of phosphate buffer(pH7.0),glucose and glutamate,32trace mineral solution,33and salt solution.2Electrode Preparation.Plain Toray carbon paper(TGPH-120, E-Tek,U.S.A.)was used as the electrode substrate in this study. Pt depositions on the electrodes were accomplished via two different methods:(1)Pt of1500Åthickness was deposited on the carbon paper electrodes using electrochemical deposition(Pt-black).The potential cycling between0.5and-2.0V at a rate of500mV/s was applied to the carbon paper electrodes,which were immersed(10)Liu,H.;Ramnarayanan,R.;Logan,B.E.Electricity generation using an air-cathode single chamber microbial fuel cell in the presence and absence of a proton exchange membrane.En V iron.Sci.Technol.2004,38,4040-4046.(11)Bennetoo,H.P.;Delaney,G.M.;Mason,J.R.;Roller,H.D.; Stirling,J.L.;Thurtson,D.F.The source of fuel cell:Efficient biomass conversion using a microbial catalyst.Biotechnol.Lett.1985,7,699-704.(12)Roller,H.D.;Bennetto,H.P.;Delaney,G.M.;Mason,J.R.;Stirling, J.L.;Thurston,D.F.Electron-transfer coupling in microbial fuel cells:1. Comparison of redox-mediator reduction rates and respiratory rates of bacteria.J.Chem.Technol.Biotechnol.1984,34B,3-12.(13)Bond,D.R.;Lovley,D.R.Electricity production by Geobacter sulfurreducens attached to electrodes.Appl.En V iron.Microbiol.2003,64, 3102-3105.(14)Rabaey,K.;Lissens,G.;Siciliano,S.D.;Verstraete,W.A microbial fuel cell capable of converting glucose to electricity at high rate and efficiency.Biotechnol.Lett.2003,25,1531-1535.(15)Tartakovsky,B.;Guiot,S.R.A comparison of air and hydrogen peroxide oxygenated microbial fuel cell reactors.Biotechnol.Prog.2006, 22,241-246.(16)Jang,J.K.;Pham,T.H.;Chang,I.S.;Kang,K.H.;Moon,H.; Cho,K.S.;Kim,H.B.Construction and operation of a novel mediator-and membrane-less microbial fuel cell.Process Biochem.(Oxford,U.K.) 2004,39,1007-1012.(17)Logan,B.E.;Murano,C.;Scott,K.;Gray,N.D.;Head,I.M. Electricity generation from cysteine in a microbial fuel cell.Water Res. 2005,39,942-952.(18)Allison,R.;Haluk,B.;Zbigniew,L.Microbial fuel cell using anaerobic respiration as an anodic reaction and biomineralized manganese as a cathodic reactant.En V iron.Sci.Technol.2005,39,4666-4671.(19)Mehta,V.;Cooper,J.S.Review and analysis of PEM fuel cell design and manufacturing.J.Power Source2003,1443,32-40.(20)Lin,R.B.;Shin,S.M.Kinetic analysis of the hydrogen oxidation reaction on Pt-black/Nafion electrode.J.Solid State Electrochem.2006, 10,243-249.(21)Paulus,U.A.;Wokaun,A.;Scherer,G.G.Oxygen reduction on carbon-supported Pt-Ni and Pt-Co alloy catalysts.J.Phys.Chem.B2002, 106,4181-4191.(22)Min,M.;Cho,J.;Cho,K.;Kim,H.Particle size and alloying effects of Pt-based alloy catalysts for fuel cell applications.Electrochim.Acta2000, 45,4211-4217.(23)Hoster,H.;Iwasita,T.;Baumga¨rtner,H.;Vielstich,W.Pt-Ru model catalysts for anodic methanol oxidation:Influence of structure and composition on the reactivity.Phys.Chem.Chem.Phys.2001,3,337-346.(24)Brankovic,S.R.;Wang,J.X.;Adzˇic´,R.R.Submonolayers on Ru nanoparticles a novel low Pt loading,High Co tolerance fuel cell electrocatalyst.Electrochem.Solid-State Lett.2001,4,A217-A220.(25)Schro¨der,U.;Niessen,J.;Scholz,F.A generation of microbial fuel cells with current output boosted by more than one order of magnitude. Angew.Chem.,Int.Ed.Engl.2003,32,2880-2883.(26)Pham,T.H.;Jang,J.K.;Chang,I.S.;Kim,B.H.Improvement of cathode reaction of a mediatorless microbial fuel cell.J.Microbiol. Biotechnol.2004,12,324-329.(27)Gasteiger,H.A.;Kocha,S.S.;Sompalli,B.;Wagner,F.T.Activity benchmarks and requirements for Pt,Pt-alloy,and non-Pt oxygen reduction catalysts for PEMFCs.Appl.Catal.,B2005,56,9-35.(28)Gasteiger,H.A.;Panels,J.E.;Yan,S.G.Dependence of PEM fuel cell performance on catalyst loading.J.Power Sources2004,27,162-171.(29)Mahlon,S.;Gottesfeld,S.High performance catalyzed membranes of ultra-low Pt loading for polymer electrolyte fuel cells.J.Electrochem. Soc.1992,139,L28-30.(30)Gasteiger,H.A.;Gu,W.;Makharia,T.;Mathias,M.F.;Sompalli,B.Beginning-of life MEA performances:efficiency loss contributions.In Handbook of fuel cells-fundamentals,technology and applications,3; Vielstich,W.,Lamm,A.,Gasteiger,H.A.,Eds.;Wiley:Chichester,U.K., 2003;Chapter46,p593.(31)Edelstein,A.S.;Cammarate,R.C.Nanomateirals:Synthesis, properties and applications,2nd ed.;Institute of Physics:London,2004; Series in Micro and Nanoscience and Technology,p433.(32)Chang,I.S.;Jang,J.K.;Gil,G.C.;Kim,M.;Kim,H.J.;Cho,B. W.;Kim,B.H.Continuous determination of biochemical oxygen demand using microbial fuel cell type biosensor.Biosens.Bioelectron.2004,19, 607-613.Effecti V e and Low-Cost Platinum Electrodes Energy&Fuels,Vol.21,No.5,20072985in a mixture solution of 1mM H 2Pt 6Cl and 100mM HCl at room temperature.(2)The other type of electrode was prepared by depositing a 1000ÅPt layer on the carbon paper using an e-beam evaporator (VE-180,Thermionics Laboratory Inc.,U.S.A.)follow-ing a manual process provided by the manufacturer.34In addition to the two types of electrodes,commercial electrodes (ELSA V2.1hand-fabricated,single-sided coatings)purchased from E-Tek were examined for comparison.Since the carbon electrode substrate consists of numerous crossed straight carbon rods,it is difficult to measure the thickness of deposited Pt layers directly.Therefore,we measured the weight of the electrode substrate before and after ing a Pt density of 21.4g/cm 3and the Pt-covered area,the equivalent thickness of Pt layers was calculated as tabulated in Table 1.This method was applied to the electrochemical as well as e-beam depositions.In addition,the thickness of e-beam deposited Pt layers was cross-checked by measuring the thickness of the Pt layer on a monitoring flat wafer that was loaded together with the carbon paper substrates into the e-beam evaporator chamber (Figure 1E).E-Beam Evaporation Process.Evaporation is one of the most frequently used methods for physical deposition.High-energy electron beams directed by a magnetic field locally melt and evaporate target materials.Then,the target vapor is deposited on the desired sample substrates.When this deposition method is used,thin films from several nanometers to 1µm can be produced with strong adhesion and high surface quality.In this study,we used an e-beam evaporation system that can hold up to a 4-in.wafer.A built-in thin-film crystal (Inficon)was used to monitor the deposition rate and thickness of the films in situ.After venting the evaporator chamber,carbon paper substrates and a crucible containing Pt pellets were loaded into the chamber.When the pressure of the chamber reached about 10-7Torr,the high voltage option on the evaporator was activated.The density and the z-ratio of Pt were set at 21.40g/cm 3and 0.245,respectively,in the manual mode.An e-beam was directed on the center of the Pt target pellets using an X -Y sweep function.After the Pt was fully melted and outgassed,the emission current was increased to 0.17A.As soon as the shutter was opened,Pt deposition started and continued until the thickness deposited on the crystal monitor reached 1000Å.Microbial Fuel Cell System.The microbial fuel cell system used is schematically illustrated in Figure 2.The anode and cathode compartments were separated by a cation exchange membrane (Nafion-112,Dupont,U.S.A.).The anode,external resistor (10Ω),and cathode were serially connected via platinum wires.2In this MFC,the anode compartment was continuously provided with nitrogen gas to maintain anaerobic conditions while the cathode compartment was provided with water-saturated air.The two compartments each contained a sheet of electrode paper (4.0cm ×1.0cm).The MFC was electrically loaded with the fixed external resistor (10Ω).The potential across the resistor was measured by a multimeter (Keithley 2701,Keithley Inc.U.S.A.),which was connected in parallel,and recorded to a personal computer through a data acquisition system 16controlled with a Labview (National Instrument Inc.U.S.A.)program.The measured potential was converted to an electric current using the following equation:current (A))potential (V)/resistance (Ω).We calculated the current density (A/m 2)using the measured current and the electrode area.Characterization of Electrode Surface.The carbon paper,Pt-black,and e-beam Pt electrodes were imaged using scanning electron microscopy (SEM;e-LiNE,Raith GmbH,Germany)set at 10.0kV.To cross-check the Pt thickness for e-beam Pt electrodes,a dummy silicon wafer was loaded together with the carbon papers into the e-beam evaporator.The thickness of the Pt layer deposited on the dummy silicon wafer was measured using atomic force microscopy (XE-100,PSIA,Korea).Results and DiscussionElectrode Characterization.Before installing the fabricated electrodes to an MFC,we first examined their microscopic structures.Two different Pt layer thicknesses (1000and 1500Å)were prepared for the Pt-black electrode using the electro-chemical deposition method,while a Pt layer of 1000Åwas deposited for the e-beam Pt electrode using the e-beam evaporator.Microscopic views of each electrode were obtained using SEM,as shown in Figure 1.Figure 1A shows a microscopic view of the carbon paper electrode without any Pt depositions.Numerous straight carbon rods cross over each other,layer-by-layer,forming a meshlike structure.When a Pt layer of 1000Åwas electrochemically deposited on the carbon rods,the color of the carbon rods changed from dark gray to shiny gray,as shown in Figure 1B.However,this color change only appeared in several top-end layers of the carbon rods while the carbon rods in the deep layers were not covered with any Pt.This was because the fresh solution in the electrochemical deposition process could not reach the deep layers during the given deposition time.As a result,the overall coverage and uniformity of the Pt layer was very poor.By increasing the amount of deposited Pt,the coverage and uniformity can be improved,as shown in Figure 1C.In this case,the thickness of the Pt layer was measured at 1500Å.Most of the area of exposed carbon rods was covered with Pt.However,the surface of the deposited surface was rough;that is,there was nonuniform Pt thickness over the electrode area.Figure 1E shows the e-beam Pt-deposited carbon rods.The entire area of the exposed carbon rods was uniformly covered with Pt,although the Pt thickness (1000Å)was lower than that of the Pt-black electrode of 1500Å(Figure 1C).Furthermore,the surface was very smooth,indicating that the deposited Pt layer thickness was highly uniform.Figure 1E shows an atomic force microscopy (AFM)image of the Pt layer edge on the dummy silicon wafer that was loaded during the e-beam-deposition process.It was confirmed from the AFM image that the thickness of the e-beam deposited Pt layer was almost 1000Å.Generally,e-beam deposition provides better coverage on projected surfaces than electrochemical deposition.As a result,given a particular thickness of the Pt layer,e-beam deposition involves less Pt loading than electrochemical deposition.In addition to this advantage,the e-beam deposition also provides strong adhesion between the electrode and the underneath carbon surface.We confirmed that the e-beam electrodes survived 1h of sonification with little damage while the Pt-black electrodes were easily segregated from the underneath surface by the sonification (data not shown).MFC Testing with Pt-Deposited Anode Electrodes.We investigated the characteristics of electricity generation in MFCs installed with different types of electrodes on the anode compartment:carbon paper electrode (case 1),Pt-black elec-trode (case 2),e-beam Pt electrode (case 3),and commercial Pt electrode (case 4)(Figure 3).The Pt thickness was 1500Åfor case 2,while it was 1000Åfor case 3.We did not test the Pt-black electrode of 1000Åsince the Pt coverage was poor,as shown in Figure 1B.As shown in Figure 3,for case 1,the current density remained steadily below 0.05A/m 2throughout(33)Diekert,G.The acetogenic bacteria.In The prokaryotes ,2nd ed.;Balows,A.,Truper,H.G.,Dworkin,M.,Harder,W.,Schleifer,K.H.,Eds.;Springer:New York,1991;pp 517-533.Table 1.Electrodes Tested in Microbial Fuel Cell (MFC)anode electrode cathode electrode thickness of Pt (Å)notecase 1carbon paper carbon paper none TGPH-120,E-TEKcase 2Pt-black carbon paper 1500electrochemical deposition case 3e-beam Pt carbon paper 1000e-beam evaporationcase 4commercial Ptcarbon paper2500Pt-black on Vulcan XC-72,E-Tekcase 5e-beam Ptcarbon paper/e-beam Pt1000e-beam evaporation case 6commercial Pt carbon paper/commercial Pt2500Pt-black on vulcan XC-72,E-Tek2986Energy &Fuels,Vol.21,No.5,2007Park et al.the testing period of 40h.For case 2,the current density was monotonically increased to 0.23A/m 2in the initial period of about 7h and remained at a similar level for the rest of the testing period.Case 4also showed a similar trend.However,it took longer to reach a peak value of 0.22A/m 2.This was due to different catalytic reactions (in case 4,the Pt as well as the Vulcan XC-72carbon catalyst on a carbon paper involved catalytic reactions).In the meantime,for case 3(e-beam Pt electrodes),the current density reached the highest value of 0.42A/m 2among the four cases,which was about 2timesgreaterFigure 1.SEM photo of carbon paper electrode,Pt-black electrode,and e-beam Pt electrode.Carbon rods on the electrode without Pt deposition (A),Pt-black 1000Å(B),Pt-black 1500Å(C),e-beam Pt 1000Å(D).AFM image of the Pt layer deposited by the e-beam evaporator on a dummy silicon wafer to monitor the deposited Pt thickness (E).Effecti V e and Low-Cost Platinum Electrodes Energy &Fuels,Vol.21,No.5,20072987than those of cases 2and 5(Pt-black and commercial electrodes,respectively).Recalling that the thickness of Pt for case 3was only 1000Å,which was thinner than that for case 2(1500Å)and case 5(2500Å),this was a remarkable improvement due mainly to the excellent coverage and uniformity of Pt for the e-beam deposition process as opposed to the electrochemical deposition process.Another distinct difference between cases 2and 3was the initial behavior in the current density.While the current density for case 2initially increased quickly and flattened out soon afterward,the current density for case 3increased very slowly for the first 10h and increased quickly after the 10h mark.Interestingly,at 24h,the current density jumped to a peak value.The second run for case 3shows a similar result.Overall,case3showed a delayed response.This delay may be attributed to slow interactions between microorganisms and the Pt catalytic layer.To understand this phenomenon fully,more in-depth studies are required.Despite the delayed response,the total area under the current density curve for case 3is comparable to that of the curve for case 2or 4,which means that the e-beam anode electrode using less Pt catalysts produces a total current density comparable to that of case 2or 4.Although data are not shown here,we observed that the current density for all the above cases monotonically decreased after hitting the peak values,as Hoster et al.reported and explained;Pt catalytic activities become deteriorated in the fuel cell due to CO poisoning during fuel oxidation.24MFC Testing with Pt-Deposited Anode and Cathode Electrodes.The results in the previous section show that Pt on the anode electrode significantly improves the current density.This section investigates the effects of Pt on MFC performance when Pt is deposited on the cathode as well as anode electrodes.Since the current density in case 1was substantially low and the current density in case 2was similar to that of case 4,our scope was more focused on the configurations of cases 3and 4.First,we installed the e-beam Pt electrodes in both the cathode and anode compartments and ran the MFC.However,the current density was similar to the current density in case 3(data not shown)without any significant improvement.The Pt layer on the cathode did not seem to have any noticeable influence on the current density.However,when the Pt electrode was installed on the cathode after a certain number of hours running with a carbon electrode on the cathode,we noticed a significant change in the current density,as shown in Figure 4.Case 5was where the carbon paper on the cathode was replaced with an e-beam Pt electrode after 45h of running the MFC under the conditions used in case 3.After the cathode electrode replacement,the current density immediately jumped to a higher level than before,and it continued to rise.The maximum current density measured 0.50A/m 2,which was higher than the first peak(0.42Figure 2.Schematic of testing microbial fuel cells.The anode and cathode compartments are separated by a cation exchange membrane.Electrodes are serially connected to a resistance (10Ω)using platinum wires and to a multimeter in parallel.The two compartments each contain a sheet of electrodes (4.0cm ×1.0cm).Figure 3.Current density when different types of electrodes are installed only on the anode (carbon paper electrode on the cathode in all the cases).Case 1(O )is for a carbon paper electrode without Pt;case 2(4)is for a Pt-black electrode (1500Å);case 3(0,O )is for an e-beam Pt electrode (1000Å),and case 4())is for a commercial Pt electrode (2500Å).2988Energy &Fuels,Vol.21,No.5,2007Park et al.A/m 2).Similarly,the cathode replacement was made on case 4;the carbon paper on the cathode was replaced with a com-mercial Pt electrode (E-Tek electrode;named case 6)after 45h of running under the same conditions as case 4.After the cathode replacement,the current density also jumped and reached a maximum value of 0.60A/m 2.For the two cases (cases 5and 6),the replacement of the carbon electrode on the cathode with the e-beam Pt electrode led to an increase in the current density,thus generating the second peaks,which were higher than the first peaks.In the mean time,it is known that replacing the electrodes in the middle of a run causes a current increase.To check this,we simply replaced the carbon cathode with a new normal carbon electrode (no Pt)after 45h of running.Similarly,we observed a jump in the current density,but its magnitude was about 40%lower than that for the e-beam Pt electrode case.The second peak in case 6(0.60A/m 2)was higher than the one in case 5(0.50A/m 2).However,considering the thickness of Pt on the electrodes,the e-beam electrodes were more effective than the commercial Pt electrodes.Figure 5shows the mass-specific current density for cases 5and 6,which was reproduced by dividing the current density by the corresponding Pt thickness.In case 5,the mass-specific current density was higher than the one in case 6during the entire range of thetesting period.The peak value for case 5was 2.5times higher than the one for case 6.This result suggests that e-beam electrodes are highly effective and cost-effective in current generation regardless of whether the Pt electrodes are installed on the anode only or on both the anode and the cathode.It is speculated that this is due mainly to the excellent coverage and strong adhesion of the e-beam Pt layer on the underneath layer.Maximum Power Density.The current density can be readily interpreted in relation to the power density.In this work,we achieved a maximum power density of 2500mW/m 2using e-beam Pt electrodes on both an anode and a cathode (case 5).This value was higher than the previous results in the litera-ture:for example,1030mW/m 2with Pt (1500Å)/nafion on a cathode in Jong et al.,35560mW/m 2with Pt (1500Å)/nafion on a cathode in Moon et al.,36and 480mW/m 2with Pt (2500Å)/PTFE and 369(mW/m 2)with Pt (2500Å)/CoTMPP on a cathode in Cheng et al.7These results indicate the potential of e-beam Pt electrodes that are practically used for MFCs.(34)VE-series vacuum coating systems general instruction manual,Thermionics laboratory Inc.,p 10-17,2007.(35)Jong,B.C.;Kim,B.H.;Chang,I.S.;Liew,P.W.W.;Choo,Y.F.;Kang,G.S.Enrichment,performance,and microbial diversity of a thermophilic mediatorless microbial fuel cell.En V rion.Sci.Technol .2006,40,6449-6454.Figure 4.Current density for cases 5(0)and 6(3).In case 5,the e-beam Pt electrode is installed on the anode while the carbon paper electrode is installed on the cathode prior to reaching 45h.In case 6,the commercial Pt electrode is installed on the anode while the carbon paper electrode is installed on the cathode prior to reaching 45h.At 45h,the carbon paper on the cathode is replaced with an e-beam Pt electrode (case 5)and a commercial Pt electrode (case6).Figure 5.The mass-specific current density that represents the current density per unit Pt thickness.This figure was produced after dividing the current density in Figure 4by the corresponding Ptthickness.Figure 6.SEM photos of Pt nanopaticle electrodes fabricated by the e-beam evaporator.(A)Nanoparticles on carbon paper and (B)a magnified view of the nanoparticles.Effecti V e and Low-Cost Platinum Electrodes Energy &Fuels,Vol.21,No.5,20072989。
第二章 物理气相沉积2真空蒸发技术PPT课件
由于采用闪烁蒸发，脉冲作用时间短，重复频率低，表
面熔蚀区只有1～10m，而靶的其他部分（包括夹具、垫
板等）处于绝热状态，不受激光加热的影响，从而保证了
蒸发原子与靶材的一致性；
由于等离子体的瞬间爆炸式发射，以及等离子体沿轴向
空间的约束效应，防止了在输运过程中出现的成份偏析；
成膜的原子、分子和离子具有极快的运动速度，增强了
⑶蒸发粒子与等离子混合体能量高，入射原子在衬底 表面的扩散剧烈。并且由于脉冲频率低，使得成膜原子的 扩散时间也足够长。因此薄膜的附着力好，易于在低温下 实现外延生长，特别适合于制作高温超导、铁电、压电、 电光等功能薄膜。
30
⑷由于等离子混合体具有极高的前向速度， 真空室中残留气体的散射作用相对减弱，因此 PLA 往 往 不 要 求 在 高 真 空 下 进 行 （ 例 如 ， 制 备 YBa2Cu3O7- 高 温 超 导 薄 膜 的 本 底 真 空 通 常 为 10Pa），简化了设备，缩短了生产周期。
26
(2) 等离子体的定向局域等温绝热膨胀发射
靶表面等离子体区继续吸收激光的能量， 产生进一步的电离，等离子体区的温度和压 力迅速升高，以等温（激光作用时）和绝热 （激光终止时）膨胀的方式沿靶面轴线向空 间中传播，传播的速度可高达105～106cm/s， 具有瞬间爆炸的形式，在空间中形成细长的 等离子体羽辉。
1000-2000 105-106
0.1Hz 105W/cm2
20-30ns 25-30ns
1-20Hz 5Hz 4J
准分子激光的特点：波长短、脉宽短、频率低
21
Read textbook! CO2激光——连续激光
材料表面温度：
Ts2(1r)P/d
P:激光功率 r:反射率 d:光点直径 k:导热系数 例：P=100W,r=0， d=1mm,k=50W/m·k 石墨表面1000 ℃， 改用粉末状镀料，导 热系数下降1个量22 级
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环形枪结构示意图（叶志镇 2008）
优点：不易污染 功率大 可蒸发高熔点材料 成膜质量较好
缺点：要求高真空 设备成本高 易污染 斑点固定 易“挖坑” 功率和效率都不高
直枪结构示意图（叶志镇 2008）
优点：使用方便 功率变化范围广 易于调节
缺点：设备体积大 结构复杂
成本高 易污染
e形枪结构示意图（叶志镇 2008）
优点：不易污染 功率大 可蒸发高熔点材料 成膜质量较好
缺点：要求高真空 设备成本高
电子束蒸发特点： 优点： 直接加热，效率高
能量密度大，蒸发高熔点材 料
冷坩埚，避免反应和蒸发 ， 提高薄膜纯度 缺点：装置复杂 残余气体和部分蒸气电离 对薄膜性能产生影响
高频感应蒸发
工作原理：线圈在高频磁场作用下因产生强大的涡流损失和 磁滞损失而升温，使材料受热蒸发。
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洁薄膜 缺点：费用高
并非所有材料均能适用
激光蒸发装置（叶志镇 2008）
反应蒸发
工作原理：在一定反应气氛中蒸发金属或低价化合物，使之在淀积过程中 发生化学反应而生成所需的高价化合物薄膜
反应蒸发法是真空镀 膜方法的一种改进
特点： 产生等离子体， 使蒸发材料和反 应气体电离活化， 提高反应效率
反应蒸发装置图（叶志镇 2008）
电阻材料：难熔金属
优点：构造简单、造价便宜、使用可靠 缺点：加热所达最高温度有限、蒸发速率较低、蒸发面积小、
不适用于高纯和高熔点物质的蒸发
电子束蒸发：将蒸发材料置于水冷坩埚中，利用电子束直接加热使蒸 发材料汽化并在衬底上凝结形成薄膜
蒸度高熔点薄膜和高纯薄膜的一种主要加热方法
电子枪由电子束聚焦方式的不同分类： 直式电子枪 环枪（电偏转） e形枪（磁偏转）
高频感应加热（叶志镇 2008）
优点：污染少 蒸发速率大 不易产生飞溅 操作简单
缺点：不能预除气 功率不能微调 装置复杂、昂
贵
激光束蒸发
工作原理：采用激光束作为蒸发材料的一种热源，让高能 量的激光束透过真空式窗口，对蒸发材料加热蒸发，通过 聚焦可使激光束功率密度提高到106w/cm2以上。
优点：可蒸发高熔点材料 热源在室外， 简化真空室 非接触加热，无污染 适于超高真空下制取纯
电子束蒸高真空环境中加热，使之升华或蒸发 并沉积在特定衬底上以获得薄膜的工艺方法
技术分类：依据蒸发源的不同
电阻热蒸发
真
电子束蒸发
空
蒸
高频感应蒸发
发
技
术
激光束蒸发
反应蒸发
电阻热蒸发
热蒸发：蒸发材料在真空室中被加热，其原子 或分子从表面逸出的现象
加热方式：电阻加热