标题: | 使用金属和新颖材料电极之有机薄膜电晶体电性行为与萧基接面特性之研究 Study on the Electrical Properties and Schottky Contact Characteristics of Organic Thin Film Transistors with Metal/Novel Material Source and Drain |
作者: | 张家豪 Chia-Hao Chang 简昭欣 杨忠谚 Chao-Hsin Chien Jung-Yen Yang 电子研究所 |
关键字: | 五环苯;薄膜电晶体;多壁奈米碳管;接触电阻;表面处理;pentacene;thin-film transistors;MWCNTs;contact resistance;surface treatment |
公开日期: | 2006 |
摘要: | 本论文制作许多以五环苯(Pentacene)为半导体层之有机薄膜电晶体,在改变不同五环苯制程条件和电极材料…等,藉由电性量测和物性观察,探讨对电晶体特性的影响和可能机制,并研究不同金属电极的电晶体特性表现和接触阻抗(Contact resistance)。以达成具有低接触阻抗、优越特性的五环苯有机薄膜电晶体。 首先改变沈积温度、沈积速率、以及薄膜厚度,五环苯制程条件,研究观察有机薄膜电晶体特性变化,以获得合适之条件,应用在后续的研究中,并探讨可能机制。其中高温和低速率的沈积有利于获得高结晶性、低缺陷的五环苯主动层,也就是较高的载子迁移率(Mobility)和电流开关比(On/off current ratio)。另外,五环苯有机薄膜电晶体在存放一特定时间后的特性退化,也有所探讨。 获取合适五环苯制程条件后,由于五环苯有机薄膜电晶体使用金属电极,也就是所谓的萧基接面,很大的接触电阻是被预期的,因此,藉由改变相同金属功函数(Work function)之电极材料,如钯(Pd)和金(Au),和接触层(Adhesion layer)厚度,观察五环苯有机薄膜电晶体的特性差异,得知五环苯和不同金属材料之接触特性差异与载子入射能障(Injection barrier)对特性的影响,以获得具优越特性的金属电极材料和合适的接触层厚度;其中较薄之接触层和使用钯作为接触金属将获得较佳之元件特性。并为进一步的提高五环苯有机薄膜电晶体特性,闸极介电层的表面处理也有所探讨和呈现;藉由特定材料(HMDS)做表面处理后,使元件之载子迁移率提升数倍。 在论文的最后,由前述之结论为基础作进一步的尝试,将多壁奈米碳管(Multi-walled carbon nanotubes, MWCNTs)作为五环苯有机薄膜电晶体之电极材料,因其与五环苯间良好的接触性质和增大的接触面积等,使可获得低接触电阻、高载子迁移率的优越结果;其中最高的载子迁移率可达0.16 cm2/Vs,电流开关比达到10^7等级。 In this thesis, pentacene thin-film transistors (pentacene TFTs) were fabricated to study the influences of pentacene deposition condition and contact material on the device performance and contact resistance. On the foundation of the results of electrical characteristics and surface morphology, the probable mechanisms of the effect of deposition conditions and contact materials on the performance were intensively discussed in attempt to achieve superior performance and low contact resistance of pentacene TFTs. By varying deposition temperature and rate, and thickness of pentacene active layer, we found that higher deposition temperature and lower deposition rate could lead to highly crystalline order and less defects in pentacene active layer, which result in turn result in higher mobility and on/off current ratio. Schottky contact between pentacene and metal electrodes results in a large unwanted contact resistance. Therefore, we used Au and Pd, which have the approximate work functions, as the contact materials. For firmly sticking Au and Pt to the substrate, Ti adhesion layer is needed. However, this additional layer will induce large injection barrier of Schottky contact because of the huge work function difference between Ti and pentacene. Thus, we also studied the effect of the adhesion layer thickness on the performance in order to get the optimized composition. From the results, pentacene TFTs with Pd as the contact material and thin Ti adhesion layer depicted superior performance because of the better contact properties and the reduced injection barrier of Pd than Au. In addition, in order to improve the performance of pentacene TFTs, HMDS surface treatments on gate dielectric was also conducted. In the final part of this thesis, we introduced multi-walled carbon nanotubes (MWCNTs) to be the contact material and studied the effects of MWCNT S/D on the performance. From the results, we found that superior performances and lower contact resistance were achieved, because of its excellent contact properties and lager contact area to pentacene. The highest mobility and on/off current ratio, and lowest contact resistance were 0.16 cm2/Vs, 10^7, 10^8 Ω-μm, respectively. |
URI: | http://140.113.39.130/cdrfb3/record/nctu/#GT009411574 http://hdl.handle.net/11536/80488 |
显示于类别: | Thesis |
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