單層石墨烯(graphene)是碳原子以SP2鍵結形成蜂巢狀排列的單原子層二維材料，石墨烯具有優異的光穿透度與良好的導電度，機械強度也極好，可應用於光電產業之透明導電層，且原料成本低廉取得容易，一旦大面積之石墨烯製備技術成熟，將有機會取代因為銦(In)原料缺乏而日益昂貴的ITO透明導電膜。
本文探討以化學插層法製備石墨烯，及其應用於透明導電膜與阻變記憶體之研究。石墨烯製備方式，主要分成兩階段：第一階段為氧化石墨片步驟，先將石墨氧化，再經過加熱膨脹，使石墨從原本層與層緊密堆積的型態分開成為單層或少層之氧化石墨( graphite oxide或稱graphene oxide，GO)，可利用掃描式探針顯微鏡量測石墨片厚度，也可由傅立葉紅外線光譜儀(FTIR)量測可得知，石墨經氧化處理後在1730cm-1處會產生C=O訊號。第二階段為還原步驟，利用幾種不同方式，其一為傳統的聯胺還原法，將聯胺加入GO溶液中加熱進行還原，但因聯胺具有劇烈反應性及毒性，因此本研究發展替代方式，利用N，N-dimethylformamide (DMF)進行還原，及可應用於石墨烯透明導電薄膜之還原製程。最後一種乃利用高溫熱裂解的方式，將GO薄膜利用真空爐管加熱至900oC，使GO內之氧原子以CO2、H2O等形式脫離進而達到還原目的。可利用FTIR量測其C=O之訊號是否消失，來確認還原與否。本研究最後利用上述方式製備石墨烯透明導電膜及石墨烯阻變記憶體元件。

Graphene is a single atomic layer of two-dimensional materials formed by carbon atoms bonded with SP2 honeycomb-like arrangement. It can be applied as transparent conductive film in opto-electronics industry with its excellent light transmittance, good electrical conductivity, and superb mechanical strength. Since the raw materials of graphene is easily accessible with low cost, it will replace ITO(indium tin oxide) as indium scarcity increases once the fabrication technology of graphene over large areas is fully-developed,.
This article explores the fabrication of graphene by chemical exfoliation, and its application for transparent conductive film and the resistive random-access memory (RRAM). The fabrication step is divided into two main parts. The first step is the oxidation of graphite. Then the graphene oxide layers can be separated to single layer or several layers graphene oxide sheet through thermal expansion. The thickness of graphene oxide layers can be measured from the scanning probe microscope. From Fourier Transform Infrared Spectroscopy (FTIR), we can find out whether the graphite was oxidized from the C=O signal(1730cm-1). The second step is the reduction of graphene oxide. Several methods were carried out. First one is the conventional method, the reduction by hydrazine, however due to the high reactivity of hydrazine and its toxicity, this method is not suitable for reduction process. Therefore, this study develops an alternative method to replace hydrazine. By using N, N-dimethylformamide (DMF) to reduce the graphene oxide, a safer method is proposed for reduction process. Another objective is to develop a process for the fabrication of the transparent conductive film which uses the high-temperature pyrolysis. By using vacuum furnace to heat the graphene oxide to high temperature, the oxygen atoms in graphene oxide would be removed in the form of CO2, H2O. We can verify completion of the reduction of graphene oxide by the absence of C=O signal(1730cm-1) from FTIR. Finally, we developed applications of the graphene made from the previous methods in fabricating transparent conductive film and RRAM.

[1] A. K. Geim K. S. Novoselov. “The rise of graphene” Nat. Mater. 8, 183-191, 2007
[2] K. S. Novoselov, A. K. Geim, S. V. Morozov, D. Jiang, Y. Zhang, S. V. Dubonos, I. V. Grigorieva,A. A. Firsov “Electric Field Effect in Atomically Thin Carbon Films” Nature. 306, 666-669, 2004
[3] Y. Zhang, J. P. Small, W.V. Pontius, and P. Kima “Fabrication and electric-field-dependent transport measurements of mesoscopic graphite devices” Appl. Phys. Lett. 86, 073014, 2005
[4]Y. Pan, D. X. Shi, H. J. Gao “Formation of graphene on Ru(0001) surface” Chin. Phys. 16, 3151-3153, 2007
[5] W. Liu, B. Li Jackson, J. Zhu, C. Q. Miao, C. H. Chung, Y. J. Park, K. Sun, J. Woo, Y.H. Xie, “Large Scale Pattern Graphene Electrode for High Performance in Transparent Organic Single Crystal Field-Effect Transistors” ACS Nano. 4, 3927-3932 , 2010
[6] Q. Yu, J. Lian, S. Siriponglert, H. Li, Y. P. Chen, S.S. Pei “Graphene segregated on Ni surfaces and transferred to insulators” Appl. Phys. Lett. 93, 113103, 2008
[7] C. A. D, D. Wei, G. Yu, Y. Liu, Y. Guo, D. Zhu “Patterned Graphene as Source/Drain Electrodes for Bottom-Contact Organic Field-Effect Transistors” Adv. Mater. 20, 3289–3293, 2008
[8] C. Berger, Z. Song, T. Li, X. Li, A. Y. Ogbazghi, R. F, Z. Dai, A. N. Marchenkov, E. H. Conrad, P. N. First, and W. A. de Heer “Ultrathin Epitaxial Graphite: 2D Electron Gas Properties and a Route toward Graphene-based Nanoelectronics” J. Phys. Chem. B, 108, 19912-19916, 2004
[9] C. Y. Su, A. Y. Lu, Y. Xu, F. R. Chen, A. N. Khlobystov, L. J. Li “High-Quality Thin Graphene Films from Fast Electrochemical Exfoliation” ACS Nano. 5, 2332-2339, 2011
[10]A. Dato, V. Radmilovic, Z. Lee, J. Phillips, M. Frenklach. “Substrate-Free Gas-Phase Synthesis of Graphene Sheets” Nano Lett. 8, 2012-2016, 2008
[11] P. Blake, P.D. Brimicombe, R. R. Nair, T. J. Booth, D. Jiang, F. Schedin, L. A. Ponomarenko, S. V. Morozov, H. F. Gleeson, E. W. Hill, A. K. Geim, K. S. Novoselov “Graphene-Based Liquid Crystal Device” Nano Lett. 8, 1704-1708, 2008
[12]B. C. Brodie. “On the Atomic Weight of Graphite” Philosophical Transactions of the Royal Society of London, 149, , 249-259, 1859
[13] L. Staudenmaier, Ber. Dtsch. Chem. Ges. 31, 1481-1487, 1898
[14]A. Clause, R. Plass, H. P. Boehm, U. Hofmann, Z. Anorg. Allg. Chem. 291, 205-220, 1957
[15]W. S. Hummers, R. Offeman. “Preparation of Graphitic Oxide” J. Am. Chem. Soc. 80, 1339, 1958.
[16] O. C. Compton, S. T. Nguyen. “Graphene Oxide, Highly Reduced Graphene Oxide, and Graphene-Versatile Building Blocks for Carbon-Based Materials” Small. 6, 711–723, 2010
[17] M. Orlita, C. Faugeras, P. Plochocka, P. Neugebauer, G. Martinez, D.K. Maude, A.-L. Barra, M. Sprinkle, C. Berger, W.A. de Heer, M. Potemski. “ Approaching the Dirac Point in High-Mobility Multilayer Epitaxial Graphene” Phys. Rev. Lett. 101, 267601, 2008
[18] C. Lee, X. Wei, J. W. Kysar, J. Hone “Measurement of the Elastic Properties and Intrinsic Strength of Monolayer Graphene” Science. 321, 385, 2008
[19] A. A. Balandin, S. Ghosh, W. Bao, I. Calizo, D. Teweldebrhan, F. Miao, C. N. Lau. “Superior Thermal Conductivity of Single-Layer Graphene” Nano Lett.8, 902, 2008
[20]R. R. Nair, P. Blake, A. N. Grigorenko, K. S. Novoselov, T. J. Booth, T. Stauber, N. M. R. Peres, A. K. Geim. “Fine Structure Constant Defines Visual Transparency of Graphene” Science. 320, 1308, 2008
[21] John A. Rogers “Making graphene for macroelectronics” Nat. Nanotechnol. 3, 254-255, 2008
[22] Y. H. Lee “Large-area graphene-based flexible transparent conducting films” NANO: Brief Reports and Reviews. 4, 83–90, 2009
[23] K. S Kim, Y. Zhao, H. Jang, S. Y. Lee, J. M. Kim, K. S. Kim, J.H. Ahn, P. Kim, J.Y. Choi, B. H. Hong “Large-scale pattern growth of graphene films for stretchable transparent electrodes” Nature. 457, 706-710, 2009
[24] H. A. Becerril, J. Mao, Z. Liu, R. M. Stoltenberg, Z. Bao, Y. S. Chen “Evaluation of Solution-Processed Reduced Graphene Oxide Films as Transparent Conductors” ACS Nano. 2, 463-470, 2008
[25] R. WaseR, M. aono. “Nanoionics-based resistive switching memories” Nat. Mater. 6, 833 – 840, 2007
[26]C. L. He, F. Zhuge, X. F. Zhou, M. Li, G. C. Zhou, Y. W. Liu, J. Z. Wang, B. Chen, . J. Su, . P. Liu, Y. H. Wu, P. Cui, R.W. Li. “Nonvolatile resistive switching in graphene oxide thin films” Appl. Phys. Lett. 95, 232101, 2009
[27] S. K. Hong, J. E. Kim, S. O. Kim, S.Y. Choi, B. J. Cho, “Flexible Resistive Switching Memory Device Based on Graphene Oxide” IEEE Electron Device Letters, 31, 1005, 2010
[28] M. Giersig, I. P.Santos, L. M. Liz-Marza “Evidence of an aggregative mechanism during the formation of silver nanowires in N,N-dimethylformamide” J. Mater. Chem. 14, 607-610, 2004
[29] P. K. Khanna, N. Singh, S. Charan, K.R. Patil “Synthesis of β-Ag2Se from organo-selenium precursor and silver nitrate in DMF via simultaneous reduction of selenium and silver salt” Mater. Lett. 60, 2080-2085, 2006
[30] A. Obut, I. Girgin “Hydrogen peroxide exfoliation of vermiculite and phlogopite” Miner. Eng. 15, 683-687, 2002
[31] L. J. Cote, F. Kim, J. X. Huang, “Langmuir−Blodgett Assembly of Graphite Oxide Single Layers”J. Am. Chem. Soc. 131, 1043-1049, 2009
[32] S. Gilje, S. Han,M.Wang, K. L.Wang, R. B. Kaner, “A Chemical Route to Graphene for Device Applications” Nano Lett. 7, 3394-3398, 2007
[33] S. Stankovich,”Synthesis of graphene-based nanosheets via chemical reduction of exfoliated graphite oxide” Carbon . 45, 1558-1565 ,2007