本實驗在無機介電層上旋轉塗佈聚甲基丙烯酸甲酯(Poly methyl methacrylate, PMMA)，改善P型材料五苯環素(pentacene)與無機材料二氧化矽間介面，並透過奈米壓印技術(NPL)改變PMMA薄膜層地形結構，使用物理氣相沉積儀在上沉積厚度60 nm的五苯環素與70 nm銀金屬電極，本論文中引入接觸轉印製作深130 nm、週期150、200、300、400、500 nm的PMMA孔洞來改變五苯環素載子傳輸層，此方法同樣具有改善五苯環素與二氧化矽間介面功能，也可以達到研究載子傳輸行為與模型之目的。
在物理薄膜分析的部分，利用掃描式電子顯微鏡(Scanning electron microscope, SEM)綜合俯視和剖面方向分析發現受到地形結構的破壞下，五苯環素的晶粒與晶界形貌隨著改變，孔洞為200 nm晶粒最小且密集，孔洞只有單顆五苯環素成核，但隨著孔洞放寬、深寬比降低，內部晶粒數上升，也在側壁坡面上出現傾斜的藥丸狀晶粒，孔洞的邊界變得模糊扭曲。而在原子力顯微鏡(Atomic force microscope, AFM)觀測下，不同週期的結構會在底部與平台出現不同樣貌，孔洞為500 nm的結構，材料在平台周圍有較大的晶粒，晶相近似於平坦的標準片，而孔洞底部的五苯環素則是受到限制，傾向垂直方向的生長，證明晶粒數量與孔洞週期成正比，直徑大小則與深寬比成反比分布。
使用GIXRD在分子維度下分析五苯環素的結晶，首先在橫向結構下，標準片的三個橫向特徵結晶點{1, ±1}、{0, 2}、{1, ±2}清晰可辨。在孔洞為150及200 nm結晶相{0, 2}、{1, ±2}強度快速消退，表示橫向生長受到孔洞寬度侷限，而無法繼續橫向堆疊。孔洞為300、400和500 nm則新增結晶相{0, 2}，雖然{1, ±2}強度不如標準片明顯，但積分結果仍比前二者小週期結構高上許多。在縱向結構下，五苯環素材料一般是一層層堆疊累積，然而，因為分子受到結構環境的限制，使得塊材相(bulk phase)提早與薄膜相(thin film phase)同時出現，也代表透過奈米結構能有效控制五苯環素的多態性。
在電性量測上，本實驗以有機場效電晶體為模型製作奈米結構之元件，分析量測電性輸出與轉換曲線，因為受到垂直方向的奈米結構與閘極電壓影響，載子從汲極到源極的傳遞受到阻礙，對載子來說，反覆通過孔洞底部與側壁並不簡單，因此奈米結構對於載子近似陷阱(traps)的存在，能在半導體與修飾層間短暫的捕捉載子並維持通道累積。以輸出電流來說，孔洞150 nm受到最密集的孔洞影響而電流最小，在轉換曲線則發現具有奈米結構的元件臨界電壓提早且遲滯現象消失。

In this study, we proposed a simple method of nanoimprinting lithography (NIL) to pattern the poly methyl methacrylate (PMMA) layer and deposited pentacene on the patterned PMMA layer. Pentacene molecules were aligned and confined by the PMMA layers with different periods of nanostructures. Through analyzing the atomic force microscope images of pentacene films, we observed that pentacene grains on the bottom of PMMA cavities were smaller than those on the flat PMMA planes. Moreover, there were pillar-like pentacene grains on the inclined laterals of PMMA cavities, indicating that the nanostructures of PMMA could affect the polymorphism of pentacene films. To investigate the polymorphism and molecular orientation of pentacene films, the grazing incidence X-ray diffractometer (GIXRD) was used. By observing two-dimensional GIXRD patterns of pentacene films, we found that both bulk and thin-film phases existed in the pentacene film with thickness less than 100 nm, differing from previous studies. This result indicates that the confinement effect on the growth of pentacene induced by the nanostructures of PMMA led to the early formation of bulk phase of pentacene. In addition, pentacene grains gradually formed on the steep laterals of PMMA cavities with increasing the thickness of pentacene films. Next, the nanoimprinted PMMA layers were adopted as the dielectrics of the pentacene-based organic field-effect transistors and the mechanism of charge transport within the devices was studied. We found that the electrical hysteresis of devices was nearly eliminated and their threshold voltage was shifted after PMMA layers were patterned by the NIL process because the PMMA cavities acted as charge traps to affect electrical characteristics of devices.

[1] Shaw, J. M., Seidler, P. F., “Organic electronics: Introduction”, IBM J. Res. Dev., 45(1), 3, 2001.
[2] Ito, T., Shirakawa, H., Ikeda, S., “Simultaneous polymerization and formation of polyacetylene film on the surface of concentrated soluble Ziegler-type catalyst solution”, J. Polym. Sci., Polym. Chem., 12, 11-20, 1974.
[3] Winokur, M., Moon, Y. B., Heeger, A. J., Barker, J., Bott, D.C., Shirakawa, H., “X-Ray Scattering from Sodium-Doped Polyacetylene: Incommensurate-Commensurate and Order-Disorder Transformations”, Phys. Rev. Lett., 58, 2329, 1987.
[4] Chiang, C., Fincher, C., Park, Y., Heeger, A., Shirakawa, H., Louis, E., MacDiarniad, A. G., “Electrical Conductivity in Doped Polyacetylene”, Phys. Rev. Lett., 39, 1098-1101, 1977.
[5] Ong, B. S., Wu, Y., and Liu, P., “High-performance semiconducting polythiophenes for organic thin-film transistors”, J. Am. Chem. Soc., 126 (11), 3378–3379, 2004.
[6] Lin, Y. Y., Gundlach, D. J., Nelson, S. F., Jackson, T. N., “Stacked pentacene layer organic thin-film transistors with improved characteristics”, IEEE Electron Device Lett., 18(12), 606-608, 1997.
[7] Jarrett, C. P., Brown, A. R., et al., “Field-effect transistor made from solution-processed organic semiconductors”, Synthetic Metals, 85(1-3), 1403-1404, 1997.
[8] Horowitz, G., “Organic field-effect transistors”, Advanced Materials, 10(5), 365-377, 1998.
[9] Tan, H. S., Mathews, N., Cahyadi, T., Zhu, F. R., Mhaisalkar, S. G., “The effect of dielectric constant on device mobilities of high-performance, flexible organic field effect transistors”, Applied Physics Lett., 94(26), 263303-1-263303-3, 2009.
[10]Peng, X. Z., Horowitz, G., “All-Organic Thin-Film Transistors Made of Alpha-Sexithienyl Semiconducting and Various Polymeric Insulating Layers”, Applied Phys. Lett., 57(19), 2013-2015, 1990.
[11]Park, K. H., Dhayal, M., “High efficiency solar cell based on dye sensitized plasma treated nano-structured TiO2 films”, Electrochemistry Communications, 11(1), 75-79, 2009.
[12] Burroughes, J. H., Bradley, D. D. C., Brown, A. R., Marks, R. N., Mackay, K., et al., “Light-emitting diodes based on conjugated polymers”, Nature, 347(6293), 539-541, 1990.
[13] Crone, B., Dodabalapur, A., Lin, Y. Y., Filas, R. W., et al., “Large-scale complementary integrated circuits based on organic transistors”, Nature, 403(6769), 521-523, 2000.
[14] Mattheus, C. C., de Wijs, G. A., de Groot, R. A., Palstra, T. T., “Modeling the polymorphism of pentacene”, J. Am. Chem. Soc., 125(20), 6323-6330, 2003.
[15] Cheng, H. L., Lin, J. W., Jang, M. F., Wu F. C., “Long-Term Operations of Polymeric Thin-Film Transistors: Electric-Field-Induced Intrachain Order and Charge Transport Enhancements of Conjugated Poly(3-hexylthiophene)”, Macromolecules, 42(21), 8251-8259, 2009.
[16] Murphy, A. R., Frechet, J. M. J., “Organic semiconducting oligomers for use in thin film transistors”, Chem. Rev., 107(4), 1066-1096, 2007
[17] Tsumura, A., Koezuka, H., Ando, T., “Macromolecular electronic device: Field‐effect transistor with a polythiophene thin film”, Applied Physics Lett., 49(18), 1210-1212, 1986.
[18] Lay-Lay Chua, Jana Zaumseil, Jui-Fen Chang, Eric C.-W. Ou, Peter K.-H. Ho, Henning Sirringhaus & Richard H. Friend, “General observation of n-type field-effect behaviour in organic semiconductors”, Nature, 434, 7030, 194, 2005.
[19] Fan, J., Yuen, J. D., Wang, M., “High-Performance Ambipolar Transistors and Inverters from an Ultralow Bandgap Polymer”, Advanced Materials, 24(16), 2186-2190, 2012.
[20] Cameron, C. G., “Enhanced rates of electron transport in conjugated-redox polymer hybrids”, PhD. Thesis, Department of Chemistry, Memorial University of Newfoundland, Canada, 2000.
[21] Dimitrakopoulos, C. D., and Malenfant, P. R. L., “Organic field-effect transistors for large area electronics”, Adv. Mater., 14(2), 99, 2002.
[22] Chou, S. Y., et al., “Nanoimprint Lithography”, J. Vac. Sci. Technol. B, 14, 4129, 1996.
[23] Zankovych, S., et al., “Nanoimprint Lithography : challenges and prospects”, Nanotechnology, 12, 91, 2001.
[24] Chou, S. Y., Krauss, P. R., “Imprint lithography with sub-10 nm feature size and high throughput”, Microelectronic Engineering, 35(1-4), 237-240, 1997.
[25] Resnick, D. J., Mancini, D., et al., “Improved step and flash imprint lithography templates for nanofabrication.” Microelectronic Engineering, 69(2-4), 412-419, 2003.
[26] Baoa, Z., Rogersb, J. A., “Thin-film Transistors From Organic Semiconducting Materials, Processing Technologies for”, Encyclopedia of Materials: Science and Technology (Second Edition), 9319-9323, 2001.
[27] Dimitrakopoulos, C. D. “Organic Field-Effect Transistors for Large-Area Electronics”, Advanced Semiconductor and Organic Nano-Techniques, 191-240, 2003.
[28] Jurchescu, O. D. “13 – Conductivity measurements of organic materials using field-effect transistors (FETs) and space-charge-limited current (SCLC) technique ”, Handbook of Organic Materials for Optical and (Opto)electronic Devices, A volume in Woodhead Publishing Series in Electronic and Optical Materials, 377–397, 2013.
[29] Lampert, M. A. “Simplified Theory of Space-Charge-Limited Currents in an Insulator with Traps”, Physical Review, 103, 1648, 1956.
[30] Rolland, J. P., Van Dam. R.M., Schorzman, D. A., Quake, S. R., DeSimone, J. M., “Solvent-resistant photocurable liquid fluoropolymers for microfluidic device fabrication”, J. Amer. Chem. Soc., 126(8), 2322-2323, 2004.
[31] Hirai, Y., Yoshikawa, T., Takagi, N., Yoshida, S., Yamamoto, K., “Mechanical Properties of Poly-methyl methacrylate (PMMA) for Nano Imprint Lithography”, J. of Photopolymer Sci. and Tec.,16(4), 615-620,2003.
[32] Ruiz, R. et. Al., “Pentacene ultrathin film formation on reduced and oxidized Si surfaces”, Physical Review B, 67, 2003.
[33]買昱椉, “五環素薄膜初期成長機制研究”, 國立成功大學博士論文, 2007
[34] Meng, Q., Jiang, L., Wei, .Z., Wang, C., Zhao, H., Li, H., Xu, W., Hu, W., Development of organic field-effect properties by aryl-acetylene into benzodithiophene.”, J. Master. Chem., 20(48), 10931-10935, 2010.
[35]薛增泉, 吳全德, 李浩, “薄膜物理”, p47-48, 電子工業出版社, 1989.
[36] Jonathan R., Stefan C. B., Mannsfeld, C. E. Miller, Alberto Salleo, Michael F. Toney, "Quantitative Determination of Organic Semiconductor Microstructure from the Molecular to Device Scale", Chem. Rev., 112, 5488-5519, 2012
[37]Hoichang, Y., Mang-Mang , L., and Lin , Y., “Temperature- Dependent Pentacene Nanostructures on Hydrophobic Gate-Dielectrics Correlated with Charge Carrier Mobilities”, J. Phys. Chem. C, 111, p12508-12511, 2007.
[38] Hwa Sung , L., Do Hwan , K., Jeong Ho , C., Minkyu , H., Yunseok , J., and Kilwon , C., “Effect of the Phase States of Self-Assembled Monolayers on Pentacene Growth and Thin-Film Transistor Characteristics”, J. Am. Chem. Soc., 130, p10556-10564, 2008.
[39]Hoichang, Y., Se, H. K., Lin, Y., Sang, Y. Y., Chan, E. P., “Pentacene Nanostructures on Surface-Hydrophobicity-Controlled Polymer/SiO2 Bilayer Gate-Dielectrics.”, Adv. Materials, 19, 2868-2872, 2007.
[40] Cheng, H. L., Mai, Y. S., Chou, W. Y., Chang, L. R., Liang, X. W., “Thickness-Dependent Structural Evolutions and Growth Models in Relation to Carrier Transport Properties in Polycrystalline Pentacene Thin Films”, Adv. Materials,17, 3639-3649, 2007.
[41]Dmitrii Nabok, Peter Puschnig, and Claudia Ambrosch-Draxl, “Crystal and electronic structures of pentacene thin films from grazing-incidence x-ray diffraction and first-principles calculations”, Physical Review b 76, 235322, 2007.