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研究生：	黃耀族 Huang, Yao-Tsu
論文名稱：	應用雙層結構於介電及電極層對P型有機薄膜電晶體效能之改善 Implementation of bilayer structure for dielectric and electrode layers to improve performance on p-type organic thin film transistors
指導教授：	蘇炎坤 Su, Yan-Kuin
學位類別：	碩士 Master
系所名稱：	電機資訊學院 - 電機工程學系碩士在職專班 Department of Electrical Engineering (on the job class)
論文出版年：	2010
畢業學年度：	98
語文別：	英文
論文頁數：	72
中文關鍵詞：	有機薄膜電晶體、五環素、雙層結構、金屬氧化物、三氧化鉬、三氧化鎢、五氧化二釩、線傳輸模型、奈米粒子、雙載子、電容、表面型態、遲滯效應
外文關鍵詞：	organic thin film transistor, pentacene, bilayer, metal oxide, MoO3, WO3, V2O5, PMMA, TLM, nanoparticle, ambipolar, capacitance, surface morphology, hysteresis
相關次數：	點閱：120 下載：4
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本論文中，針對五環素有機薄膜電晶體，藉由應用雙層結構於介電層和電極層，有效的改善元件的效能。
對於電極層的雙層結構，我們應用不同種類金屬氧化物(三氧化鉬, 三氧化鎢, 五氧化二釩)在金屬電極和半導體之間。這些金屬氧化物在有機薄膜電晶體主要的角色是充當載子注入層，藉由平衡半導體和金屬電極的能階的不對稱，同時在介面間形成歐姆接觸。特別是以低工作函數的金屬(鋁)當電極的元件, 電特性的改善尤其明顯，其中包括至少高兩級的輸出飽和電流和開關比，以及臨界電壓從 -24V下降到 -9 V。我們利用了線傳輸模型(TLM)來導出有機薄膜電晶體的接觸電阻，用以證實金屬氧化物在介面間歐姆機觸的確實形成。當元件使用MoO3當載子注入層，其接觸電阻從2.1 MΩ 下降到 0.1 MΩ。
在這份研究的另一部分，是利用奈米粒子和PMMA修飾表面所形成的雙層結構介電層，來提升絕緣層的電容值。進而我們探討了奈米粒子層和PMMA修飾層厚度的改變, 對電子特性的影響。在這份研究中，我們用了兩種不同的奈米粒子(SiO2, Al2O3)作為比較。當使用奈米粒子雙層結構的介電層時，兩種奈米粒子都可以發現雙載子(ambipolar)傳輸特性，這種特性在使用PMMA當單一層的絕緣層時，並無法產生進行n-type的操作。其它絕緣層的一些特性像是電容、表面型態、遲滯效應等對元件特性的影響也在研究範圍內。和相似厚度的單層的高分子介電層的元件比較，奈米粒子雙層結構的元件主在效能改善在於電容值從5.6 nF/cm2上升到12 nF/cm2，因此輸出飽和電流有效的提昇至少一個等級。最後，我們計算了雙層結構的奈米氧化矽在有機薄膜電晶體中，載子移動率在高電壓和低電壓應用方面，表現數值分別為0.78 cm2/Vs 和0.025 cm2/Vs。

In this thesis, the performances of pentacene-based OTFTs had been successfully improved by employing bilayer structure for electrode and dielectric layer.
The bilayer electrodes consists of a metal oxides(MoO3, WO3, V2O5) interlayer between semiconductor(pentacene) and metal electrodes such as Au and Al. The major roles of metal oxides in OTFT was to act as charge injection layer as a result of aligning mismatch of energy level between metal and semiconductor as well as formed ohmic contact at interface. Electrical performances improvement was particularly observed for device with low-work-function metal electrode such as Al, including at least two orders higher in saturation induced current and On/Off ratio as well as lower threshold voltage from -24 V to -9 V. The extraction of contact resistance (Rc) on top-contact OTFTs from TLM was used to characterize the surface property in order to prove the interface with metal oxide did ohmic, and contact resistance was reduced from 2.1 MΩ to 0.1 MΩ if device utilized MoO3 as interlayer.
Another section in this thesis is to increase capacitance by utilizing nanoparticles and smooth by PMMA polymer to form bilayer gate dielectric. The influence of thickness for PMMA modified layer and nanoparticles layer to electrical properties had been investigated. Two types of nanoparticles(SiO2, Al2O3) were used for comparison in this work. Ambipolar behavior in output characteristics was observed for both nanoparticle used as bilayer gate dielectric, pentacene-based OTFT did not exhibit n-channel transport as using PMMA for single layer dielectric. The device properties influenced by gate dielectric such as capacitance, surface morphology, hysteresis behavior had been characterized. Comparing with the single layer polymeric dielectric, the major improvement for bi-layer dielectric structure were higher capacitance from 5.6 (nF/cm2) to 12 (nF/cm2) with similar gate dielectric thickness, therefore electrical properties such as induced current was increased at least one order. Mobility in saturate regime for OTFTs with nano-SiO2 bilayer gate dielectric was calculated, which was 0.78 (cm2/Vs) and 0.025 (cm2/Vs) for high-voltage and low-voltage applications respectively.

Abstract (in Chinese) .....................................I 
Abstract (in Engilsh) ...................................III 
Acknowledgement ...........................................V 
Content...................................................VI 
Table Captions .........................................VIII 
Figure Captions..........................................XII 

Chapter 1 Introduction....................................1 
1-1 Application of organic thin-film transistors...1 
1-2 OTFT Structures................................1 
1-3 Pentacene-based organic thin film transistors..2 
1-4 Organic thin-film transistors with polymeric gate dielectric ...........................................2 
1-5 Influence factors to performances of OTFT .....3 
Chapter 2 Principles of Organic Thin-Film Transistors .....6 
2.1 Charge carriers transport in organic semiconductor .............................................6 
2.2 Organic TFT operation .........................6 
2.3 Electrical properties of organic TFTs .........7 
Chapter 3 Experiment procedure and Measurement ...........14 
3-1 Materials.....................................14 
3-2 OTFT device fabrication procedure ............15 
3-3 Measurement ..................................16 
Chapter 4 Results and Discussions.........................25 
4-1 Metal-Oxide carriers injection layers between Electrodes/Semiconductor .................................26 
4-1-1 Fixed thickness of Metal oxide interlayer with Au electrodes ............................26 
4-1-2 Fixed thickness of Metal oxide interlayer with Al electrodes ............................28 
4-1-3 Contact resistance(Rc) extracted by Transmission Line Model ..................................29 
4-1-4 Thickness of metal oxides interlayers ..........................................................30 
4-2 Nanoparticles bi-layer gate dielectrics ......31 
4-2-1 Thickness changing of PMMA modified layer ....................................................31 
4-2-2 Thickness changing of SiO2 nanoparticles layer ......................................33 
4-2-3 Comparison between different nanoparticles dielectric materials .......................34 
4-2-3(a) Output characteristics and ambipolar behavior .......................................34 
4-2-3(b) Transfer characteristics and hysteresis ..........................................35 
4-2-3(c) Surface morphology ......36 
4-2-3(d) Capacitance and dielectric constant .................................................36 
Chapter 5 Conclusions and Future Prospect ................64 
5-1 Conclusions ..................................64 
5-2 Future Prospect ..............................65 
Reference ................................................67 

Figure 1-1. Schematic view of top-contact and bottom-contact ...................................................5 
Figure 1-2. Output characteristics for ambipolar OTFT......5 
Figure 2-1. Hopping model for carriers conduction ........11 
Figure 2-2. π-orbital overlap in Benzene ................11 
Figure 2-3. P-type operation in OTFT .....................12 
Figure2-4. Typical electrical behaviors for OTFT .........13 
Figure 3-1. Chemical structure of PMMA ...................18 
Figure 3-2. Chemical structure of Pentacene ..............18 
Figure 3-3. Device Structure .............................19 
Figure 3-4. Process Flow to fabricate OTFT ...............19 
Figure 3-5. Thermal vacuum evaporation system ............20 
Figure 3-6. Masks designed for thermal evaporation a) mask for pentacene deposit b) mask to define source/drain......21 
Figure 3-7. Top view of top-contact Pentacene-based OTFTs ..........................................................21 
Figure 3-8. Configuration of two 2400 sourcemeters for electrical characteristics measurement....................22 
Figure 3-9. AFM for morphology characterization ..........23 
Figure 3-10. (a) The conducting path between source and drain, total resistance is divided into a series of five resistive elements b) Rc extracted from TLM at various gate voltages .................................................24 
Figure 4-1. Contact angles on surface on PMMA ............39 
Figure 4-2. Contact angles on surface on pentacene .......39 
Figure 4-3. Device structure of OTFT with metal oxide interlayer ...............................................40 
Figure 4-4. Work function of Au and Al as well as energy band diagram for metal oxide and Pentacene ...............40 
Figure 4-5. Output characteristics for the devices with Au electrode (a) Control sample without metal oxide interlayer (b) sample with 6 nm thickness of MoO3 interlayer (c) sample with 6 nm thickness of V2O5 interlayer (d) sample with 6 nm thickness of WO3 interlayer ....................41 
Figure 4-6. Transfer characteristics for the devices with Au electrode (a) Sub-threshold Swing and On/OFF Ratio (b) Threshold Voltage ........................................42 
Figure 4-7. Output characteristics for the devices with Al electrode (a) control sample without metal oxide interlayer (b) sample with 6 nm thickness of MoO3 interlayer (c) sample with 6 nm thickness of V2O5 interlayer (d) sample with 6 nm thickness of WO3 interlayer ....................43 
Figure 4-8. Transfer characteristics for the devices with Al electrodes (a) Sub-threshold Swing and On/OFF Ratio (b) Threshold Voltage ........................................44 
Figure 4-9. (a) The computed RT vs. drain voltage for devices with/without MoO3 interlayer. (b) The RT for different channel lengths at same drain and gate voltage. The strain line fit to y-intercept is representing Rc ....46 
Figure 4-10. Output characteristics in various thicknesses for different metal oxides interlayers a) MoO3 b) V2O5 c) WO3 ......................................................48 
Figure 4-11. Transfer characteristics in various thicknesses for different metal oxides interlayers a) MoO3 b) V2O5 c) WO3 ..........................................50 
Figure 4-12. Device structure for a) control sample with PMMA insulator and b) bi-layer dielectrics ...............51 
Figure 4-13. TEM image: 20nm SiO2 nanoparticles dispersing in Ethylene Glycol solvent ...............................51 
Figure 4-14. Output characteristics for bilayer structure by 530nm thickness of SiO2 nanoparticles with PMMA modified layer a) 5% PMMA (260nm) b) 5% PMMA (240nm) c) 3% PMMA (200nm) d) 3% PMMA(120nm) ...............................52 
Figure 4-15. Transfer characteristics for bilayer structure by 530nm thickness of SiO2 nanoparticles with various thicknesses of PMMA modified layer .......................53 
Figure 4-16. Hysteresis behaviors of OTFTs with bilayer dielectric by 530nm thickness of SiO2 nanoparticles with PMMA modified layer a) 5% PMMA (260nm) b) 5% PMMA (240nm) c) 3% PMMA (200nm) d) 3% PMMA (120nm) ...................54 
Figure 4-17. Output characteristics for bilayer structure by various thickness of SiO2 nanoparticles with fixed 120nm thickness PMMA modified layer a) SiO2: 340nm b) SiO2: 220nm ..........................................................55 
Figure 4-18. Transfer characteristics for bilayer structure by various thickness of SiO2 nanoparticles with fixed 120nm thickness PMMA modified layer ............................56 
Figure 4-19. Hysteresis behaviors for bilayer structure by various thickness of SiO2 nanoparticles with fixed 120nm thickness PMMA modified layer a) SiO2: 340nm b) SiO2: 220nm ..........................................................56 
Figure 4-20. Output characteristics for different dielectric layers structure: a) PMMA only b) PMMA/nano-SiO2 c) PMMA/nano-Al2O3 .......................................57 
Figure 4-21. Output characteristics in N-channel for bilayer structure a) PMMA/nano-SiO2 b) PMMA/nano-Al2O3 ...58 
Figure 4-22. Transfer characteristics for different dielectric layers structure ..............................59 
Figure 4-23. Hysteresis behavior for different dielectric layers structure: a) PMMA only b) PMMA/nano-SiO2 c) PMMA/nano-Al2O3 ..........................................60 
Figure 4-24. Surface morphology of bilayer dielectric by AFM a) PMMA/nano-SiO2 b) PMMA/nano-Al2O3 ...............61 
Figure 4-25. AFM images of pentacene films deposited on a) PMMA/nano-SiO2 b) PMMA/nano-Al2O3 ........................61 
Figure 4-26. Capacitances-Voltage curve at 1k Hz for single-layer/bilayer gate dielectrics ...........................62 

Table 4-1. Summary of electric properties for devices with Au / Metal-Oxides and Al / Metal-Oxides contact...........45 
Table 4-2. Comparison of Pentacene-based OTFTs with single-layer / bilayer gate dielectric extracted from IDS-VGS at VDS=-40 V and VGS=-40V ........................63 
Table 4-3. Electric properties for Pentacene-based OTFTs with bilayer nano-SiO2 gate dielectric extracted from IDS-VGS at VDS=-10 V and VGS=-10V ........................63 
                                    

[1] Christos D. Dimitrakopoulos, Patrick R. L. Malenfant, “Organic Thin Film Transistors for Large Area Electronics”, Adv. Mater., 14, No. 2 (2002)
[2] Antonio Facchetti, Myung-Han Yoon, Tobin J. Marks, “Gate dielectrics for organic field-effect transistors: New opportunities for organic electronics”, Adv. Mater., 17, 1705-1725 (2005)
[3] Thokchom Birendra Singh, Farideh Meghdadi, Serap Gunes, Nenad Marjanovic, Gilles Horowitz, Philippe Lang, Siegfried Bauer, Niyazi Serdar Sariciftci, “High-Performance Ambipolar Pnetacene Field-Effect Transistors on Poly(vinyl alcohol) Organic Gate dielectric”, Adv. Mater., 17, 2315-2320 (2005)
[4] B. Chandar Shekar, Jiyeon Lee and Shi-Woo Rhee, ”Organic Thin Film Transistors: Materials, Processes and Devices”, Korean J. Chem. Eng., 21, 267-285 (2004)
[5] J. Puigdollers, C. Voz, A. Orpella, R. Quidant, I. Martin, M. Vetter, R. Alcubilla, ”Pentacene thin-film transistors with polymeric gate dielectric”, Organic Electronics, 5, 67–71 (2004)
[6] Hong Ma, Hin-Lap Tip, Fei Huang, Alex K.-Y. Jen, “Interface engineering for organic electronics“, Adv. Funct. Mater., 20, 1-18 (2010)
[7] S. W. Cho, D. S. Park, W. C. Jang, M.-H. Cho, K.-H. Yoo, K. Jeong, C.-N. Whang, Y. Yi, K. B. Chung, ”Electronic structure of Pentancene/ultrathin gate dielectric interface for low-voltage organic thin film transistors”, J. Appl. Phys., 102, 064502 (2007)
[8]Roland Schmechel, Hezine von Seggern, “Electronic traps in organic transport layers“, Phys. stat. sol., 201, No. 6, 1215-1235 (2004)
[9] Dong Guo, Tetsuhiko Miyadera, Susumu Ikeda, Toshihiro Shimada, Koichiro Saiki, “Analysis of charge transport in a polycrystalline Pentacene TFT by temperature and gate bias dependent mobility and conductance”, J. Appl. Phys., 102, 023706 (2007)
[10] Marta Tello, Marco Chiesa, Claudia M. Duffy, and Henning Sirringhaus, “Charge Trapping in Intergrain Regions of Pentacene Thin Film Transistors”, Adv. Funct. Mater., 18, 1–7 (2008)
[11] Henning Sirringhaus, “Reliability of Organic Field-Effect Transistors”, Adv. Mater., 21, 1–15 (2009)
[12] Wei-Yang Chou, Chia-Wei Kuo, Horng-Long Cheng, Yi-Ren Chen, Fu-Ching Tang, Feng-Yu Yang, Dun-Yin Shu, Chi-Chang Liao,” Effect of surface free energy in gate dielectric in pentacene thin-film transistors”, Appl. Phys. Lett., 89, 112126 (2006)
[13] P. Lara Bullejos, J. A. Jiménez Tejada, F. M. Gómez-Campos, M. J. Deen, O. Marinov, “Evaluation of the charge density in the contact region of organic thin film transistors”, J. Appl. Phys., 106, 094503 (2009)
[14] Janos Veres, Simon D. Ogier, Stephen W. Leeming, Domenico C. Cupertino, Soad Mohialdin Khaffaf, “Low-K Insulators as the Choice of Dielectrics in Organic Field-Effect Transistor”, Adv. Funct. Mater., 13, No. 3 (2003)
[15] Robert A. Street, “Thin-Film Transistors”, Adv. Mater., 21, 2007–2022 (2009)
[16] K. P. Pernstich, S. Haas, D. Oberhoff, C. Goldmann, D. J. Gundlach, B. Batlogg, A. N. Rashid, G. Schitter, “ Threshold voltage shift in organic field effect transistors by dipole monolayers on the gate insulator”, J. Appl. Phys., Vol. 96, No. 11 (2004)
[17] Yunlong Guo, Yunqi Liu, Chong-an Di, Gui Yu, Weiping Wu, Shanghui Ye, Ying Wang, Xinjun Xu, Yanming Sun, “Tuning the threshold voltage by inserting a thin molybdenum oxide layer into organic field-effect transistors”, Appl. Phys. Lett., 91, 263502 (2007)
[18] Sung Hun Jin, Keum Dong Jung, Hyungcheol Shin, Byung-Gook Park, Jong Duk Lee, “Grain size effects on contact resistance of top-contact pentacene TFTs”, Synthetic. Metals., 156, 196-201 (2006)
[19]Y. Shao, S. A. Solin, D. R. Hines, E. D. Williams,”The effect of transfer printing on pentacene thin-film crystal structure”, J. Appl. Phys., 100, 044512 (2006)
[20] Yeon Taek Jeong, Ananth Dodabalapur, “Pentacene-based low voltage organic field- effect transistors with anodized Ta2O5 gate dielectric” Appl. Phys. Lett., 91, 193509 (2007)
[21] D. Knipp, R. A. Street, A. Volkel, J. Ho,“ Pentacene thin film transistors on inorganic dielectrics: Morphology, structural properties, and electronic transport”, J. Appl. Phys., Vol. 93, No. 1, (2003)
[22] Tsung-Syun Huang, Yan-Kuin Su, Po-Cheng Wang, “Study organic thin film transistor with polymethylmethacrylate as a dielectric layer”, Appl. Phys. Lett., 91, 092116 (2007)
[23] Horng-Long Cheng, Yu-Shen Mai, Wei-Yang Chou, Li-Ren Chang, “Influence of molecular structure and microstructure on device performance of polycrystalline pentacene thin-film transistors”, Appl. Phys. Lett., 90, 171926 (2007)
[24] Jun Li, Xiao-Wen Zhang, Liang Zhang, Khizar-ul Haq, Xue-Yin Jiang, Wen-Qing Zhu Zhi-Lin Zhang, ” Performance enhancement of organic thin-film transistors using WO3-modified drain/source electrodes”, Semicond. Sci. Technol, 24, 115012 (2009)
[25] Antonio Facchetti, Tobin J. Marks, “Transparent Electronics: From Synthesis to Applications”, John Wiley & Sons Ltd., p352, (2010)
[26] Chih-Wei Chu, Sheng-Han Li, Chieh-Wei Chen, Vishal Shrotriya, Yang Yang, “High-Performance organic thin film transistors with metal oxide/metal bilayer electrode”, Appl. Phys. Lett. 87, 193508(2005)
[27] Y. Baia, X. Liua, L. Chena, Khizar-ul-Haqa, M.A. Khana, W.Q. Zhu, X.Y. Jianga, Z.L. Zhang, “Organic thin-film field-effect transistors with MoO3/Al electrode and OTS/SiO2 bilayer gate insulator”, Microelectronics Journal, 38,1185-1190 (2007)
[28] Jeong-Woo Park, Kang-Jun Baeg, Jieun Ghim, Seok-Ju Kang, Jeong-Ho Park, and Dong-Yu Kim, “Effects of Copper Oxide/Gold Electrode as the Source-Drain Electrodes in Organic Thin-Film Transistors”, Electrochemical and Solid-State Lett., 10 (11), H340-H343 (2007)
[29] Feng-Yu Yang, Kuo-Jui Chang, Meei-Yu Hsu, Cheng-Chin Liu, “Low-operating-voltage polymeric transistor with solution-processed low-k polymer/high-k metal-oxide bilayer insulators”, Org. Electr. (2008), doi:10.1016/j.orgel.2008.06.002
[30] Chang Su Kim, Sung Jin Jo, Sung Won Lee, Woo Jin Kim, Hong Koo Baik, Se Jong Lee, “Surface-Modified High-k Oxide Gate Dielectrics for Low-Voltage High-Performance Pentacene Thin-Film Transistors”, Adv. Funct. Mater., 17, 958-962 (2007)
[31] Cheon An Lee, Dong-Wook Park, Keum-Dong Jung, Byung-ju Kim, Yoo Chul Kim,
Jong Duk Lee, Byung-Gook Park, “Hysteresis mechanism in pentacene thin-film transistors with poly(4-vinyl phenol) gate insulator”, Appl. Phys. Lett. 89, 262120 (2006)
[32] J. H. Schon, S. Berg, Ch. Kloc, B. Batlogg, “ Ambipolar Pentacene Field-Effect Transistors and Inverters”, Science, vol. 287, (2000)
[33] Takeshi Yasuda, Takeshi Goto, Katsuhiko Fujita, Tetsuo Tsutsui, “Ambipolar pentacene field-effect transistors with calcium source-drain electrodes”, Appl. Phys. Lett., Vol. 85, No. 11 (2004)
[34] Th. B. Singh, P. Senkarabacak, N. S. Sariciftci, A. Tanda, C. Lackner, R. Hagelauer, Gilles Horowitz, “Organic inverter circuites employing ambiploar pentacene field-effect transistors”, Appl. Phys. Lett., 89, 033512 (2006)
[35] Taishi Takenobu, Kazuhiro Watanabe, Yohei Yomogida, Hidekazu Shimotani, Yoshihiro Iwasa, “Effect of postannealing on the performance of pentacene single crystal ambipolar transistors”, Appl. Phys. Lett., 93, 073301 (2008)
[36] Kouji Suemori, Sei Uemura, Manabu Yoshida, Satoshi Hoshino, Noriyuki Takada,
Takehito Kodzasa, Toshihide Kamata, “ Threshold voltage stability of organic field effect transistors for various chemical species in the insulator surface”, Appl. Phys. Lett., 91, 192112 (2007)
[37] Janos Veres, Simon Ogier, Giles Lloyd, “Gate Insulators in Organic Field-Effect Transistors”, Chem. Mater., 16, 4543-4555 (2004)
[38] Tianhong Cuia, Guirong Liang, “Dual-gate pentacene organic field-effect transistors based on a nanoassembled SiO2 nanoparticle thin film as the gate dielectric layer”, Appl. Phys. Lett., 86, 064102 (2005)

校內：2011-08-11公開
校外：2011-08-11公開

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