本論文研究以五苯（pentacene）有機分子半導體為主動層之薄膜電晶體，探討五苯的薄膜結構與電傳輸性質的關係。研究分兩部份，第一部份，探討無機介電層對五苯有機薄膜電晶體（OTFT）的電特性影響；第二部份，使用高分子材料修飾介電層表面，利用成長不同厚度的五苯薄膜，探討有機薄膜電晶體的載子傳輸性質。
第一部份:探討不同介電層表面能對成長五苯薄膜結構的影響，並探討相關薄膜電晶體的電特性。利用接觸角量測介電層表面能；使用X-ray繞射，量測五苯薄膜的結晶結構。結果指出，介電層的表面能會明顯影響五苯薄膜的成長與結晶結構。較強的X-ray繞射峰暗指較佳的結晶結構，其載子傳輸效率較佳。發現當五苯薄膜厚度為70 nm時，有較佳的載子傳輸效率。
第二部份:利用高分子polymethylmethacrylate （PMMA）修飾二氧化矽介電層表面，於其上成長不同厚度的五苯薄膜，並製作薄膜電晶體元件。利用原子力顯微鏡、X-ray繞射、與拉曼光譜研究五苯薄膜的結構與形態學。結果指出，五苯薄膜成長於有PMMA修飾層的介電層上，可獲致較佳的結晶結構與較強的分子間振動耦合能，其載子遷移率明顯優於僅使用二氧化矽介電層的元件，載子遷移率最高可達1.1 cm2/Vs。而且，五苯電晶體元件的載子遷移率與五苯厚度相關，當薄膜厚度小於70 nm時，載子遷移率隨厚度增加而增加，當薄膜厚度大於70 nm時，載子遷移率則隨厚度增加而減少。最後，我們發現五苯薄膜表面的晶粒大小與薄膜電晶體的載子遷移率並無直接相關。

In this study, the electronic transport properties and device characteristics of polycrystalline pentacene-based organic thin film transistors (OTFTs) were investigated. In part 1, we studied the electric characteristics of pentacene-based OTFTs using several different inorganic gate dielectrics. In the second part, we have investigated the electrical transport properties of pentacene films with various thicknesses as the active layer in OTFTs using the gate dielectrics with a polymeric modification layer.
Part 1: The influence of the surface energy of gate dielectrics on the thin film structure of pentacene and the corresponding device characteristics of OTFTs were studied. The surface properties of gate dielectrics and the structure of pentacene films were investigated using contact angle measurement and x-ray diffraction, respectively. Results revealed that the surface energy of a dielectric has a strong impact on the growth of pentacene films and the performance of pentacene-based OTFTs.
Part 2: The pentacene films with various thicknesses were deposited upon a polymethylmethacrylate (PMMA) layer and their characteristics were analyzed using atomic force microscope, x-ray diffraction, and Raman spectroscopy. Here, we have used a PMMA layer that served as a modification layer upon silicon dioxide (SiO2) gate dielectric. Structural analysis revealed that the pentacene films grown on PMMA with better crystal structure and stronger intermolecular vibrational coupling as compared to that grown on native SiO2 surface. It resulted in a higher mobility of above 1.1 cm2 / Vs which is close to two orders of magnitude improvements than that using a conventional SiO2 gate dielectric layer. Furthermore, clear thickness-dependent field-effect mobility of pentacene-base OTFTs was also observed. The results suggested an optimal thickness of around 70 nm of pentacene active layer. Finally, we have not observed direct relationship between the grain size and the performance of pentacene-based OTFTs.

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