於有機薄膜電晶體(Organic thin-film transistor, OTFT)的五苯環通道層與源極/汲極電極間加入氟化鋰緩衝層可增進載子的注入效率與元件的效率，而氟化鋰緩衝層的最佳厚度為1.0 nm，加入此厚度的有機薄膜電晶體元件場效載子移動率與接觸電阻分別為 0.376 cm2/Vs與0.6 GΩ-μm。根據上述的實驗結果，使用氟化鋰緩衝層加入有機薄膜電晶體的五苯環通道層與源極/汲極電極間，將是一種改善有機薄膜電晶體特性簡單且具有效率的方法。
接著我們探究通道層厚度與基板升溫對元件特性的影響。實驗結果可得最佳通道層厚度為 30 nm，最佳基板升溫溫度為 90 ℃。而最佳通道層厚度與基板升溫條件的有機薄膜電晶體元件場效載子移動率為0.823 cm2/Vs，最後於最佳條件的有機薄膜電晶體中加入1.0 nm 的緩衝層氟化鋰，而場效載子移動率達到1.176 cm2/Vs。

The LiF buffer layer inserted between pentacene active layer and Au source/drain electrodes of OTFTs can improve the efficiency of the carrier injection. The optimal thickness of LiF buffer layer was 1.0 nm. The resulted field-effect mobility and contact resistance of OTFT devises with inserting LiF buffer layer were 0.376 cm2/Vs and 0.6 GΩ-μm, respectively. According to the results mentioned above, the LiF buffer layer inserted between pentacene active layer and Au source/drain electrodes of OTFTs is a simple and efficient way to improve the electrical performances of the resulted OTFTs.
Then we investigate the effect of channel layer thickness and substrate temperature. The optimal thickness of channel layer was 30 nm and the optimal temperature of substrate was 90 ℃. The resulted field-effect mobility of OTFT devises with optimal channel layer thickness and substrate temperature were 0.823 cm2/Vs. Finally, the optimal OTFT devises with 1.0nm LiF buffer layer was fabricated, the field-effect mobility was 1.176 cm2/Vs.

[1] C. K. Chiang, C. R. Fincher Jr., Y. W. Park, A. J. Heeger, H. Shirakawa, E. J. Louis, S. C. Gau, and A. G. MacdDiarmid, “Electrical Conductivity in Doped Polyacetylene”, Phys. Rev. Lett., 39, 1098 (1977).
[2] F. Garnier, R. Hajlaoui, A. Yassar, and P. Srivastava, “All-Polymer Field-Effect Transistor Realized by Printing Techniques”, Science, 265, 1684 (1994).
[3] N. J. Watkins, L. Yan, and Y. Gao, “Electronic structure symmetry of interfaces between pentacene and metals”, Appl. Phys. Lett., 80, 4384 (2002).
[4] H. Peisert, M. Knupfer, and J. Fink, “Energy level alignment at organicOmetal interfaces: Dipole and ionization potential”, Appl. Phys. Lett., 81, 2400 (2002).
[5] J. M. Zhao, S. T. Zhang, X. J. Wang, Y. Q. Zhan, X. Z. Wang, G. Y. Zhong, Z. J. Wang, X. M. Ding, W. Huang, and X. Y. Hou, “Dual role of LiF as a hole-injection buffer in organic light-emitting diodes”, Appl. Phys. Lett., 84, 2913 (2004).
[6] S. T. Zhang, X. M. Ding, J. M. Zhao, H. Z. Shi, J. He, Z. H. Xiong, H. J. Ding, E. G. Obbard, Y. Q. Zhan, W. Huang, and X. Y. Hou, “Buffer-layer-induced barrier reduction: Role of tunneling in organic light-emitting devices”, Appl. Phys. Lett., 84, 425 (2004).
[7] X. J. Wang, J. M. Zhao, Y. C. Zhou, X. Z. Wang, S. T. Zhang, Y. Q. Zhan, Z. Xu, H. J. Ding, G. Y. Zhong, H. Z. Shi, Z. H. Xiong, Y. Liu, Z. J. Wang, E. G. Obbard, X. M. Ding, W. Huang, and X. Y. Hou, “Enhancement of electron injection in organic light-emitting devices using an Ag/LiF cathode”, J. Appl. Phys., 95, 3828 (2004).
[8] F. Ebisawa, T. Kurokawa, and S. Nara, “Electrical properties of polyacetylene/polysiloxane interface”, J. Appl. Phys., 54, 3255 (1982).
[9] A. Tsumura, H. Koezuka, and T. Ando, “Macromolecular electronic device: Field-effect transistor with a polythiophene thin film”, Appl. Phys. Lett., 49, 1210 (1986).
[10] V. C. Sundar, J. Zaumseil, V. Podzorov, E. Menard, R. L. Willett, T. Someya, M. E. Gershenson, and J. A. Rogers, “Elastomeric Transistor Stamps: Reversible Probing of Charge Transport in Organic Crystals”, Science, 303, 1644 (2004).
[11] S. M. Sze, “Physics of Semiconductor Device”, Wiley (1981).
[12] N. J. Watkins, L. Yan, and Y. Gao, “Electronic structure symmetry of interfaces between pentacene and metals”, Appl. Phys. Lett., 80, 4384 (2002).
[13] F. Amy, C. Chan, and A. Kahn, “Polarization at the gold/pentacene interface”, Org. Chem., 6, 85 (2005).
[14] K. Ihm, H. E. Heo, S. Chung, J. R. Ahn, J. H. Kim, and T. H. Kang, “Odd characteristics of Au film on pentacene”, Appl. Phys. Lett., 90, 242111 (2007).
[15] Y. E. Kim, H. Park, and J. J. Kim, “Enhanced quantum efficiency in polymer electroluminescence devices by inserting a tunneling barrier formed by Langmuir–Blodgett films”, Appl. Phys. Lett., 69, 599 (1996).
[16] L. S. Hung, C. W. Tang, and M. G. Mason, “Enhanced electron injection in organic electroluminescence devices using an Al/LiF electrode”, Appl. Phys. Lett., 70, 152 (1997).
[17] F. Li, H. Tang, J. Anderegg, and J. Shinar, “Fabrication and electroluminescence of double-layered organic light-emitting diodes with the Al2O3 /Al cathode”, Appl. Phys. Lett., 70, 1233 (1997).
[18] Z. B. Deng, X. M. Ding, S. T. Lee, and W. A. Gambling, “Enhanced brightness and efficiency in organic electroluminescent devices using SiO2 buffer layers”, Appl. Phys. Lett., 74, 1227 (1999).
[19] S. E. Shaheen, G. E. Jabbour, M. M. Morrell, Y. Kawabe, B. Kippelen, N. Peyghambarian, M. F. Nabor, R. Schlaf, E. A. Mash, and N. R. Armstrong, “Bright blue organic light-emitting diode with improved color purity using a LiF/Al cathode”, J. Appl. Phys., 84, 2324 (1998).
[20] G. Daniel, B. Paul, K. Krishna, and Z. Jie, “Printed Organic and Molecular Electronics”, Kluwer Academic Pub (2004).
[21] T. S. Huang, Y. K. Su and P. C. Wang, “Study of organic thin film transistor with polymethylmethacrylate as a dielectric layer”, Appl. Phys. Lett., 91, 092116 (2007).
[22] W. Wang, J. Shi, W. Jiang, S. Guo, H. Zhang, B. Quan and D. Ma, “High-mobility pentacene thin-film transistors with copolymer-gate dielectric”, Microelectron. J., 38, 27 (2007).
[23] E. Ito, H. Oji, H. Ishii, K. Oichi, Y. Ouchi, and K. Seki, “Interfacial electronic structure of long-chain alkane/metal systems studied by UV-photoelectron and metastable atom electron spectroscopies”, Chem. Phys. Lett., 24, 137 (1998).
[24] N. J. Watkins, L. Yan, and Y. Gao, “Electronic structure symmetry of interfaces between pentacene and metals”, Appl. Phys. Lett., 80, 4384 (2002).
[25] G. Horowitz, M. E. Hajlaoui, and R. Hajlaoui, “Temperature and gate voltage dependence of hole mobility in polycrystalline oligothiophene thin film transistors”, J. Appl. Phys., 87, 4456 (2000).
[26] J. Lee, K. Kim, J. H. Kim, S. Im, and D. Y. Jung, “Optimum channel thickness in pentacene-based thin-film transistors”, Appl. Phys. Lett., 82, 4169 (2003).
[27] W. Wang, J. Shi, W. Jiang, S. Guo, H. Zhang, B. Quan, and D. Ma, “High-mobility pentacene thin-film transistors with copolymer-gate dielectric”, Microelectron. J., 38, 27 (2007).
[28] J. Lee, J. H. Kim, and S. Im, “Effects of substrate temperature on the device properties of pentacene-based thin film transistors using Al2O3+x gate dielectric”, J. Appl. Phys., 95, 3733 (2004).
[29] A. D. Carloa, F. Piacenza, A. Bolognesi, B. Stadlober, and H. Maresch, “Influence of grain sizes on the mobility of organic thin-film transistors”, Appl. Phys. Lett., 86, 263501 (2005).
[30] D. J. Gundlach, Y. Y. Lin, T. N. Jackson, S. F. Nelson, and D. G. Schlom, “Influence of grain sizes on the mobility of organic thin-film transistors”, IEEE Electron Device Lett., 18, 87 (1997).