臺灣博碩士論文加值系統

本論文研究以五苯（Pentacene）為主動層之薄膜結構性質與薄膜電晶體電特性，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，研究五苯成長於無機介電層與不同高分子修飾層表面的薄膜結構性質，使用八種高分子絕緣材料，包括polymethylmethacrylate (PMMA)、poly(vinyl alcohol) (PVA)、poly(vinyl pyrrolidone) (PVNP)、polyfluorene (PF)、poly(vinylidene fluoride) (PVDF)、polyimide (PI)、polyethyleneimine (PEI)、與polystyrene (PS)。第二部份，研究高分子絕緣材料修飾不同的二氧化矽基板對五苯有機薄膜電晶體電特性的影響，探討五苯於不同高分子修飾層上的載子傳輸性質。
第一部份：研究不同介電層材料之表面特性對於成長五苯薄膜結構性質的影響。本實驗利用接觸角量測介電層與五苯表面自由能，研究介電層與五苯層間附著力對五苯薄膜結構的影響；利用下列實驗進行五苯薄膜結構分析：原子力顯微鏡觀察表面形態、X-ray繞射量測結晶結構、拉曼光譜分析振動特性與微結構、與吸收光譜量測基態到激發態的電子躍遷性質。結果指出，高分子介電層與五苯的界面附著力與高分子的總表面自由能並無明確關係，然而，高分子非極性項表面自由能則與五苯間的附著力呈正相關﹔五苯成長於不同高分子修飾層表面，呈現多樣化的表面晶粒型態，指出高分子的表面性質對五苯薄膜的初期成長影響甚大，其中，五苯成長於PVNP表面具有最大的晶粒尺度﹔XRD 繞射結果指出五苯成長於PI、PMMA、與PEI表面有較佳的結晶結構﹔拉曼振動光譜分析指出五苯成長於PI、PMMA、PVNP、與PEI有較大的分子間作用力、有較佳的分子微結構、與環境均勻性，而且五苯延基板法線成長（縱向）的結晶尺度愈大，五苯分子間振動耦合能通常也愈大；吸收光譜分析建議這些五苯薄膜有近似的π-π*能隙，成長於PMMA上的五苯薄膜有最大的Davydov 分裂，指出有較大的分子間作用力。綜合上述分析，高分子的表面性質明顯影響五苯成膜機制與薄膜結構，其中又以PMMA較適合成長五苯薄膜，可獲得最佳的結晶結構、較強的分子間作用力、以及較好的薄膜均勻性。
第二部份:利用高分子絕緣材料修飾不同表面特性的二氧化矽介電層表面，並製作五苯薄膜電晶體元件。當使用高分子材料修飾較粗糙的二氧化矽表面，五苯薄膜電晶體有較佳的載子傳輸效率。分析五苯薄膜縱向結晶結構、表面晶粒大小、分子間振動耦合能、與高分子/五苯界面間的附著力，並無法完全解釋五苯薄膜結構與載子傳輸的相關性。吾人進一步發現高分子修飾層的絕緣效果明顯影響五苯電晶體的電傳輸特性，因此建議當製作有機薄膜電晶體時，不同特性的介電層基板需搭配適合的高分子絕緣材料，如PS適合修飾較平坦的二氧化矽表面，PVNP則可用於修飾較粗糙的二氧化矽表面，應用此概念，吾人己經成功研製高性能的五苯薄膜電晶體，使用PVNP當介電修飾層，場效載子遷移率可達1∼2 cm2/Vs。

In this study, the structural and electronic transport properties of polycrystalline pentacene thin-films grown on various gate dielectric surfaces, including inorganic and polymeric insulators, were investigated using organic thin films transistors (OTFTS) with top contact configuration. The study was divided into two parts; in the first part we studied the structural properties of a series of pentacene films grown on inorganic and polymeric insulator surfaces. The polymeric insulator was used as a modification layer upon silicon dioxide (SiO2), including polymethylmethacrylate (PMMA), poly(vinyl alcohol) (PVA), poly(vinyl pyrrolidone) (PVNP), polyfluorene (PF), poly(vinylidene fluoride) (PVDF), polyimide (PI), polyethyleneimine (PEI), and polystyrene (PS). For the second part of this study we investigated the influence of these polymeric modification layers on the electronic characteristics of pentacene-based OTFT devices.
Part I: The influence of surface properties of various gate dielectric surfaces on the surface morphology, crystal structure, surface free energy, molecular vibrational characteristics and microstructure, as well as π-π* electronic transitions of a series of polycrystalline pentacene films have been investigated using atomic force microscopy (AFM), X-ray diffraction (XRD), contact angle meter, Raman spectroscopy, and absorption spectroscopy. We found that the interfacial adhesive force between the pentacene layer and the dielectric surface are independent of the total surface energy of polymeric surfaces, but dependent on the dispersion force components of polymeric surface free energy. When pentacene was grown on different polymeric surfaces, the pentacene films exhibited variety grainy texture morphology. Among the, these morphologies, pentacene film on PVNP has the largest grain size. We therefore suggest that the polymeric surface properties have a great influence on the first stage of pentacene growth. XRD results indicated the pentacene films on PI, PMMA, and PEI have better crystal quality than that on other polymeric surfaces. Raman analysis results indicated that the pentacene films on PI, PMMA, PVNP, and PEI have large intermolecular coupling energy (w1) and better film homogeneity. Furthermore, we observed a positive relationship between the w1 and the crystal quality along the vertical direction of substrate of these pentacene films on various surfaces. Analysis of the absorption spectrum indicated that these pentacene films have a similar value as the π-π* gap. However, pentacene film on PMMA has the largest Davydov splitting, thus stronger intermolecular interactions. When compared to the pentacene films on other dielectric surfaces, we suggest that the film on PMMA could have superior carrier transport properties due to better crystal quality, larger intermolecular interactions, and homogeneous microstructure.
Part 2: The pentacene films with thicknesses of 600 A were grown on polymeric buffer layers, which deposited upon the SiO2 dielectrics with different surface properties, and the corresponding pentacene-based OTFTs were studied. When the polymeric insulators modified the rough SiO2 surface, the corresponding pentacene-based OTFTs showed better field-effect mobilities (μ) as compared to that on a smooth SiO2 surface. We could not observe clear relationships between the �� and the crystal quality, grain size, w1, and interfacial adhesive force of pentacene on the polymeric surfaces. Moreover, we found that the insulation ability of these polymeric insulators play an important role in the electronic transport properties of pentacene-based OTFTs. To make the OTFTs with a polymeric modification layer upon gate dielectrics, the polymeric properties should be considered on a case by case basis for different surface characteristics of gate dielectrics. For example, the PS suit modifies smooth SiO2 surfaces and the PVNP modifies rough SiO2 surfaces, thus improved charge transport efficiency of pentacene-based OTFTs were obtained. Based on the concepts, we have successfully fabricated pentacene-based OTFTs with a high mobility up to 1-2 cm2/Vs.

中文摘要 ..............................................I
Abstract ..............................................IV
誌謝 ..............................................VII
目次 ..............................................VIII
表目錄 ................................................XI
圖目錄 ................................................XII
第 1 章 有機薄膜電晶體簡介 ..............................1
1-1 前言 ................................................1
1-2 有機半導體傳輸機制 .............................3
1-3 有機薄膜電晶體概論 .............................4
1-3-1 有機薄膜電晶體基本結構 ....................4
1-3-2 有機薄膜電晶體操作原理 ....................5
1-3-3 有機薄膜電晶體基本電特性 ....................6
1-4 本論文研究目的 ......................................8
第 2 章 實驗方法與分析工具 .............................14
2-1 實驗材料 ......................................14
2-1-1 有機半導體材料 .............................14
2-1-2 二氧化矽絕緣材料 .............................14
2-1-3 高分子絕緣材料 .............................15
2-2 元件製程 ......................................16
2-2-1 基板清洗 ......................................16
2-2-2 旋轉塗佈 ......................................16
2-2-3 熱蒸鍍成長五苯與金屬電極 ....................17
2-3 分析工具 ......................................17
2-3-1 接觸角 ......................................18
2-3-2 原子力顯微鏡 ......................................19
2-3-3 X-ray薄膜繞射儀 .............................20
2-3-4 拉曼散射量測系統 .............................21
2-3-5 紫外光-可見光吸收光譜儀 ....................23
2-3-6 電性分析 ......................................24
第 3 章 高分子修飾層表面特性對於五苯有機薄膜成長之影響..34
3-1 前言 ...............................................34
3-2 實驗方法 ......................................36
3-2-1 元件材料 ......................................36
3-2-2 元件製作 ......................................36
3-2-3 分析工具 ......................................36
3-3 高分子修飾層與五苯有機薄膜特性分析 ...........37
3-3-1 表面能量測分析 .............................37
3-3-2 原子力顯微鏡結果與分析 ....................39
3-3-3 X-ray繞射分析 .............................41
3-3-4 拉曼散射光譜量測與分析 ....................43
3-3-5 紫外-可見光吸收光譜分析 ....................47
3-4 綜合討論 ......................................49
第 4 章 探討高分子修飾層對五苯有機薄膜電晶體電特性影響 ..79
4-1 前言 ...............................................79
4-2 實驗方法 ......................................81
4-2-1 元件材料 ......................................81
4-2-2 元件製作 ......................................81
4-2-3 分析工具 ......................................82
4-3 五苯有機薄膜電晶體電特性分析 ....................82
4-3-1 電性量測分析 ......................................82
4-3-2 薄膜結構與電性關係探討 ....................83
4-3-3 遲滯效應 ......................................85
4-4 綜合討論 ......................................86
第 5 章 總結與未來展望 .............................97
參考文獻 ...............................................99

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