本論文研究以五苯（Pentacene）有機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，探討無機介電層與高分子修飾層表面性質對於有機薄膜電晶體的電特性影響；第二部份，使用不同分子量的polymethylmethacrylate（PMMA）高分子絕緣材料修飾二氧化矽介電層表面，成長五苯薄膜並製作有機薄膜電晶體，探討高分子絕緣材料分子量對於有機薄膜電晶體的載子傳輸性質的影響。
第一部份:探討不同介電層表面特性對成長五苯薄膜結構與製作之五苯有機薄膜電晶體電性的影響。利用電性量測結果，比較在不同介電層表面特性上的五苯有機薄膜電晶體電特性；利用接觸角量測介電層表面能；使用原子力顯微鏡觀察五苯薄膜的表面形態；使用X-ray繞射量測五苯薄膜的結晶結構；利用拉曼光譜分析五苯薄膜分子微結構。結果指出，高分子絕緣材料旋轉塗佈在較粗糙的介電層表面時，可使五苯有機薄膜電晶體的載子傳輸效率較佳。最後，我們建議五苯薄膜的垂直結構與載子傳輸效率並沒有直接關係。
第二部份:利用不同分子量的PMMA修飾二氧化矽介電層表面，於其上成長400 Å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，五苯薄膜成長於分子量較大的PMMA修飾層上，可獲致較佳的結晶結構與較強的分子間振動耦合能，其場效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1.44 cm2/Vs。而且，PMMA修飾層分子量愈大使得五苯電晶體元件的場效載子遷移率也愈大。最後，我們發現五苯薄膜厚度400 Å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 structural and electrical transport properties of polycrystalline pentacene films on inorganic dielectrics and polymeric modification layers were investigated using organic thin films transistors (OTFTs) with top contact configuration. In part 1, we studied the influence of surface properties of inorganic dielectrics and polymeric modification layers on the morphology of pentacene films and electrical characteristics of pentacene-based OTFTs. In part 2, we studied the effects of molecular weight of polymeric modification layers on the pentacene film growth and the relevant electrical transport properties in pentacene-based OTFTs.
Part 1: We have fabricated the pentacene thin films on PMMA and on SiO2 surfaces featuring the different surface energy and surface roughness. The surface properties of gate dielectric layers and structure of pentacene films have been investigated using contact angle meter, atomic force microscopy (AFM), X-ray diffraction (XRD), and Raman spectroscopy. On PMMA surfaces the pentacene films displayed the high crystal quality from XRD scans, although the film on PMMA with significantly smaller grain size. Finally, high performance tiny grain polycrystalline pentacene-based thin-film transistors, including a PMMA dielectric modification layer, were produced.
Part 2: The pentacene films with thicknesses 400 Å were grown on the PMMA buffer layers with different molecular weight, which deposited upon SiO2 gate dielectrics, and the corresponding pentacene-based OTFTs were studied. The structure of pentacene films were characterized by AFM, XRD, and Raman spectroscopy. Structural analysis revealed that the pentacene films grown on PMMA with better crystal structure and stronger intermolecular coupling as compared to that grown on native SiO2 surface, especially on that using large molecular weight PMMA. It resulted in a higher field-effect mobility of above 1.44 cm2 / Vs which is close to one order of magnitude improvements than that using a conventional SiO2 gate dielectric layer. Finally, we have not observed direct relationship between the grain size and the performance of pentacene-based OTFTs.

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