石墨烯具備良好的電、光、熱、磁、化以及機械性質，因此非常適合用於研發新式的奈米元件，而其特殊的光電效應也使的石墨烯成為具有很高的潛力光感測器研究材料。
雖然石墨烯具有很寬廣的吸收頻譜，但是其對於光子的吸收與轉換效率低弱，因此雖然因為其優異的電子遷移率所以擁有多關於電子元件的應用問世，但是微弱的光響應反而使的石墨烯光學感測元件發展之路受到了一定的限制。
在本論文中，主要以CVD熱化學氣相沉積法成長高品質連續薄膜石墨烯，為了避免基板內部於量測時的干涉，所以將其轉移至石英基板，並利用黃光微影的方式完成元件的製作，並搭配RAMAN、SEM、AFM分析。石墨烯與金屬電極所形成的p-p+-p結構於常溫大氣中，利用不同波長的二極體雷射進行照射，包含藍光(405nm)、綠光(532nm)、紅光(633nm)，實驗並探討石墨烯的光響應機制。從實驗結果中除了可以發現到於低電壓時可以觀察到的金屬-石墨烯接面的光伏效應，於高電壓時因為高品質石墨烯材料本身具有的彈道式載子傳輸，導致光激發與載子間所造成的散射現象，可以產生近10-3 A的強烈負光導效應，十分具有研究價值。
除此之外我們還利用真空腔體與偏光鏡，分析於不同環境對石墨烯的參雜效應與不同雷射光源功率時的光響應強度變化。為了提升光響應的效果我們除了利用一般電極，還利用不同形狀的金屬電極，目的是為了降低暗電流，增加響應電流的變化量。

Graphene possesses excellent electrical, photonic, magnetic, chemical and mechanical properties for applications to nanoscale devices. Due to its extraordinary electronic and optical properties, which accommodate a large potential in optoelectronic applications such as photodetection.
Monolayer graphene is transparent in a wide spectrum and absorbs photons inefficiently. Therefore, although graphene has been studied extensively for electronic applications due to its excellent carrier mobility, poor photo-response and low photo-output-current make graphene based photo-detectors less desirable than many of the semiconductor counterparts.
In the experiment, we grow graphene by chemical vapor deposition process. In order to prevent the supporting substrate from altering the electronic and transport significantly, we used quartz as the substrate. The device was fabricated and analyzed by using photolithography, Raman system, scanning electron microscopy (SEM) and atomic force microscope (AFM). We report an Au-graphene-Au p-p+-p photodetector operating in ambient environments at room temperature with output signal current greater than 10-3A, which is generated by negative photoconductivity of graphene due to photo-excitation and photo-ionization enhanced carrier-carrier scattering involving quasi-ballistic carriers in the dark current driven by an applied voltage.
In addition, a vacuum chamber and a polarizer was used to analyze the doping effects of graphene and the laser power dependence of photoresponse. The photoresponse current was observed to increase with dark current.

[1] Bardeen, J. and W. H. Brattain (1948). "The transistor, a semi-conductor triode." Physical Review 74(2): 230, 1948.

[2] Geim, A. K. and K. S. Novoselov (2007). "The rise of graphene." Nature materials 6(3): 183-191, 2007.

[3] Bonaccorso, F., Z. Sun, T. Hasan and A. C. Ferrari "Graphene photonics and optoelectronics." Nature Photonics 4(9): 611-622, 2010.

[4] Novoselov, K. S., A. K. Geim, S. Morozov, D. Jiang, Y. Zhang, S. Dubonos, I. Grigorieva and A. Firsov (2004). "Electric field effect in atomically thin carbon films." science 306(5696): 666-669, 2004.

[5] Singh, V., D. Joung, L. Zhai, S. Das, S. I. Khondaker and S. Seal (2011). "Graphene based materials: past, present and future." Progress in Materials Science 56(8): 1178-1271, 2011.

[6] Kim, K. S., Y. Zhao, H. Jang, S. Y. Lee, J. M. Kim, K. S. Kim, J.-H. Ahn, P. Kim, J.-Y. Choi and B. H. Hong (2009). "Large-scale pattern growth of graphene films for stretchable transparent electrodes." Nature 457(7230): 706-710, 2009.

[7] Li, X., G. Zhang, X. Bai, X. Sun, X. Wang, E. Wang and H. Dai (2008). "Highly conducting graphene sheets and Langmuir–Blodgett films." Nature nanotechnology 3(9): 538-542, 2008.

[8] Berger, C., Z. Song, X. Li, X. Wu, N. Brown, C. Naud, D. Mayou, T. Li, J. Hass and A. N. Marchenkov (2006). "Electronic confinement and coherence in patterned epitaxial graphene." Science 312(5777): 1191-1196, 2006.

[9] De Heer, W. A., C. Berger, X. Wu, P. N. First, E. H. Conrad, X. Li, T. Li, M. Sprinkle, J. Hass and M. L. Sadowski (2007). "Epitaxial graphene." Solid State Communications 143(1): 92-100, 2007.

[10] Zhang, Y., J. P. Small, W. V. Pontius and P. Kim (2005). "Fabrication and electric-field-dependent transport measurements of mesoscopic graphite devices." Applied Physics Letters 86(7): 073104-073104-073103, 2005.

[11] Yu, Q., J. Lian, S. Siriponglert, H. Li, Y. P. Chen and S.-S. Pei (2008). "Graphene segregated on Ni surfaces and transferred to insulators." Applied Physics Letters 93(11): 113103, 2008.

[12] Li, X., W. Cai, J. An, S. Kim, J. Nah, D. Yang, R. Piner, A. Velamakanni, I. Jung and E. Tutuc (2009). "Large-area synthesis of high-quality and uniform graphene films on copper foils." Science 324(5932): 1312-1314, 2009.

[13] Li, X., W. Cai, I. H. Jung, J. H. An, D. Yang, A. Velamakanni, R. Piner, L. Colombo and R. S. Ruoff (2009). "Synthesis, characterization, and properties of large-area graphene films." ECS Transactions 19(5): 41-52, 2009.

[14] Li, X., Y. Zhu, W. Cai, M. Borysiak, B. Han, D. Chen, R. D. Piner, L. Colombo and R. S. Ruoff (2009). "Transfer of large-area graphene films for high-performance transparent conductive electrodes." Nano letters 9(12): 4359-4363, 2009.

[15] Bae, S., H. Kim, Y. Lee, X. Xu, J.-S. Park, Y. Zheng, J. Balakrishnan, T. Lei, H. R. Kim and Y. I. Song (2010). "Roll-to-roll production of 30-inch graphene films for transparent electrodes." Nature nanotechnology 5(8): 574-578, 2010.

[16] Ni, Z., H. Wang, J. Kasim, H. Fan, T. Yu, Y. Wu, Y. Feng and Z. Shen (2007). "Graphene thickness determination using reflection and contrast spectroscopy." Nano letters 7(9): 2758-2763, 2007.

[17] Blake, P., E. Hill, A. C. Neto, K. Novoselov, D. Jiang, R. Yang, T. Booth and A. Geim (2007). "Making graphene visible." Applied Physics Letters 91(6): 063124, 2007.

[18] JJung, I., M. Pelton, R. Piner, D. A. Dikin, S. Stankovich, S. Watcharotone, M. Hausner and R. S. Ruoff (2007). "Simple approach for high-contrast optical imaging and characterization of graphene-based sheets." Nano Letters 7(12): 3569-3575, 2007.

[19] Paredes, J., S. Villar-Rodil, P. Solis-Fernandez, A. Martinez-Alonso and J. Tascon (2009). "Atomic force and scanning tunneling microscopy imaging of graphene nanosheets derived from graphite oxide." Langmuir 25(10): 5957-5968, 2009.

[20] Vlassiouk, I., M. Regmi, P. Fulvio, S. Dai, P. Datskos, G. Eres and S. Smirnov (2011). "Role of hydrogen in chemical vapor deposition growth of large single-crystal graphene." Acs Nano 5(7): 6069-6076, 2011.

[21] Malard, L., M. Pimenta, G. Dresselhaus and M. Dresselhaus (2009). "Raman spectroscopy in graphene." Physics Reports 473(5): 51-87, 2009.

[22] Emtsev, K. V., A. Bostwick, K. Horn, J. Jobst, G. L. Kellogg, L. Ley, J. L. McChesney, T. Ohta, S. A. Reshanov and J. Röhrl (2009). "Towards wafer-size graphene layers by atmospheric pressure graphitization of silicon carbide." Nature materials 8(3): 203-207, 2009.

[23] Ferrari, A., J. Meyer, V. Scardaci, C. Casiraghi, M. Lazzeri, F. Mauri, S. Piscanec, D. Jiang, K. Novoselov and S. Roth (2006). "Raman spectrum of graphene and graphene layers." Physical review letters 97(18): 187401, 2006.

[24] Biswas, C., F. Güneş, D. D. Loc, S. C. Lim, M. S. Jeong, D. Pribat and Y. H. Lee (2011). "Negative and positive persistent photoconductance in graphene." Nano letters 11(11): 4682-4687, 2011.

[25] Docherty, C. J., C.-T. Lin, H. J. Joyce, R. J. Nicholas, L. M. Herz, L.-J. Li and M. B. Johnston (2012). "Extreme sensitivity of graphene photoconductivity to environmental gases." Nature communications 3: 1228, 2012.

[26] Giovannetti, G., P. Khomyakov, G. Brocks, V. Karpan, J. Van den Brink and P. Kelly (2008). "Doping graphene with metal contacts." Physical Review Letters 101(2): 026803, 2008.

[27] Lee, E. J., K. Balasubramanian, R. T. Weitz, M. Burghard and K. Kern (2008). "Contact and edge effects in graphene devices." Nature nanotechnology 3(8): 486-490, 2008.

[28] Xu, X., N. M. Gabor, J. S. Alden, A. M. van der Zande and P. L. McEuen (2009). "Photo-thermoelectric effect at a graphene interface junction." Nano letters 10(2): 562-566, 2009.

[29] Gabor, N. M., J. C. Song, Q. Ma, N. L. Nair, T. Taychatanapat, K. Watanabe, T. Taniguchi, L. S. Levitov and P. Jarillo-Herrero (2011). "Hot carrier–assisted intrinsic photoresponse in graphene." Science 334(6056): 648-652, 2011.

[30] Liu, Y., R. Cheng, L. Liao, H. Zhou, J. Bai, G. Liu, L. Liu, Y. Huang and X. Duan (2011). "Plasmon resonance enhanced multicolour photodetection by graphene." Nature communications 2: 579, 2011.