Epitaxial graphene synthesis, characterization, and devices

EPITAXIAL GRAPHENE: SYNTHESIS, CHARACTERIZATION, AND DEVICES RAM SEVAK SINGH (M.Tech., IIT Kharagpur) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF PHYSICS NATIONAL UNIVERSITY OF SINGAPORE (2012) DECLARATION i ACKNOWLEDGEMENT A journey is easier when you travel together. Interdependence is certainly more valuable than independence. This thesis is the result of four years of work whereby I have been accompanied and supported by many people. It is a pleasant aspect that I have now the opportunity to express my gratitude for all of them. It is with a feeling of profound gratitude and regards that I acknowledge the invaluable guidance and encouragement rendered to me by my deeply respected supervisor Professor Andrew Wee Thye Shen of the Department of Physics, National University of Singapore throughout the course of my Ph.D. work. Without the meticulous care and attention with which he supervised me and constantly reviewed the entire work it would not have been possible to carry out the work to this level. He reviewed my manuscripts, whole thesis, and gave many precious suggestions to my thesis. He also supported me by granting research assistantship to me during the writing of thesis. I would like to thank my co-supervisor, Assistant Professor Chen Wei, for his positive support and help during my Ph.D. programme. He also reviewed my manuscripts and thesis and gave me many valuable suggestions to my thesis. I am also thankful to Professor Ji Wei for supporting me to initiate a work of graphene-based photoconductive device. I gained fruitful experiences by discussing with him. No list would be complete without thanks to the most important people in my life. My parents, my brother, my sisters can never be thanked enough for the unconditional love. ii The chain of my gratitude would be definitely incomplete if I would forget to thank the first cause of this chain, The Prime Mover who drives the entire world. Winding up with a quote from a Robert Frost’s poem “…And miles to go before I sleep”, I pray to Lord to bestow me with the power to dream and ability to achieve. iii LIST OF PUBLICATIONS International Journals 1. Ram Sevak Singh, Venkatram Nalla, Wei Chen, Andrew Thye Shen Wee, Wee Ji,“Laser Patterning ofEpitaxial Graphene for Schottky Junction Photodetectors”, ACS NANO, 5, 5969 (2011). 2. Ram Sevak Singh, Venkatram Nalla, Wei Chen, Wei Ji, Andrew T. S. Wee, “Photoresponse in epitaxial graphene with asymmetricmetal contacts”, APPLIED PHYSICS LETTERS, 100, 093116 (2012). Selected for the March 19, 2012 issue of virtual journal of nanoscale science and technology. 3. Ram Sevak Singh, Xiao Wang,Wei Chen, Ariando,Andrew. T. S. Wee, “Large room-temperature quantum linear magnetoresistance in multilayered epitaxial graphene: Evidence for two-dimensional magnetotransport.” APPLIED PHYSICS LETTERS, 101, 183105 (2012). 4. Ram Sevak Singh, Qihua Xiong, Wei Chen, Andrew Thye Shen Wee, “High-gain photodetectors based on oxygen plasma treated epitaxial graphene.” (In preparation) Conference Presentation 1. Ram Sevak Singh, Venkatram Nalla, Wei Chen, Wei Ji, Andrew T. S. Wee. (2012) Photoresponse in epitaxial graphene with asymmetricmetal contacts. The 5th MRS-S Conference on Advanced Materials. Nanyang Executive Centre, NTU, Singapore. 2. Ram Sevak Singh) Venkatram Nalla, Wei Chen, Andrew Thye Shen Wee, Wee Ji. Laser Patterning of Epitaxial Graphene for Schottky Junction Photodetectors. (2011) Spintronics in Graphene Conference. University Hall, National University of Singapore, Singapore. iv Patent Ram Sevak Singh,Venkatram Nalla, Chen Wei, Wee ATS, Ji Wei, “Laser Patterning of Graphene/Graphene-oxide Schottky Juction forPhotoconductive and Photovoltaic Applications” US, 61/515,380, Sep 2011 (Provisional). v TABLE OF CONTENTS Chapter 1. Literature background 1.1. Fundamentals of graphene 1.2. Properties of graphene 1.2.1. Crystal and electronic structures 1.2.2. Electronic transport 1.2.3. Graphene optical properties .6 1.3. Potential applications of graphene .8 1.3.1. Spin-valve devices .9 1.3.2. Sensors .10 1.3.3. Graphene based optolectronic devices .11 1.3.4. Other applications 14 1.4. Motivation . 15 1.5. Objectives .16 Chapter 2. Methodology and characterization techniques 18 2.1. Methodology 18 2.2. Overview of ultra high vacuum (UHV) system and characterization techniques………………………………………… .19 2.2.1. UHV systems 19 2.2.2. STM 20 2.3. AFM . 24 2.4. Raman spectroscopy 29 2.4.1. Raman spectroscopy as a characterization tool for graphene vi materials .32 2.5. Hall effect measurement and physical property measurement system (PPMS) . 34 Chapter 3. Synthesis and characterization of epitaxial graphene on Si-face SiC … 40 3.1. Introduction .40 3.2. Temperature-dependent formation of EG on Si-face SiC substrate: in-situ EG growth monitoring by STM 42 3.3. EG film characterization using AFM and Raman spectroscopy measurements 46 3.3.1. AFM measurements .46 3.3.2. Raman singnatures and EG layers determination 47 3.3.3. Evidence of strain in EG 50 3.4. Hall measurements: electrical properties of EG 51 3.4.1. Materials and devices fabrication 51 3.4.2. Hall measurements 52 3.4.3. Results and discussion .53 3.5. Conclusion .55 Chapter 4. Photoconductive devices based on pristine and laser modified epitaxial graphene .57 4.1. Introduction 57 4.1.1. Laser patterning of epitaxial graphene for Schottky junction photodetectors……………………………………… 62 vii 4.1.1.1. Materials and characterization .62 4.1.1.2. Laser patterning and characterization 64 4.1.1.3. EG-LEG-EG photodetector .69 4.1.1.3.1. Position-dependent photoresponse observation .70 4.1.1.3.2. Temporal photocurrent profiles 72 4.1.1.3.3. Spectral photoresponse investigation 74 4.1.1.3.4. Interdigitated EG-LEG-EG device .76 4.1.1.4. Infrared absorption spectrum of LEG .78 4.1.1.5. EG-LEG-EG characteristics summary, comparison and advantages 79 4.1.2. Photoresponse in EG with asymmetric metal contacts… 81 4.1.2.1. Materials and device fabrication . 81 4.1.2.2. Photoconductive response of Au-EG-Al device, and influence of EG active layers 84 4.1.2.3. Au-EG-Al characteristics summary, comparison and advantages 89 4.1.2.4. Conclusion 90 Chapter 5. High-gain photodetectors based on oxygen plasma treated epitaxial graphene 92 5.1. Introduction 92 5.2. Materials and device fabrication 94 5.3. Oxygen plasma treatments of EG device .95 5.4. Device measurements 96 5.5. Results and discussion 97 viii 5.5.1. Photoconductive response .97 5.5.2. Photoelectron spectroscopy (PES) investigation 99 5.5.3. Temperature-dependent resistance and Arrhenius plot 101 5.5.4. Raman measurements 102 5.5.5. Possible photoresponse mechanism .103 5.5.6. Light intensity-dependent photoresponse . 105 5.5.7. Spectral photoresponse .107 5.6. Applications 113 5.7. Conclusion .114 Chapter 6. Magnetotransport studies of multilayer EG on C-face SiC 115 6.1. Introduction .115 6.2. Material synthesis 120 6.3. Device fabrication and characterization .121 6.3.1. Raman characterization 121 6.3.2. Surface morphology and thickness determination using AFM .123 6.4. Magnetotransport measurements .125 6.5. Results and Discussion .125 6.5.1. Room temperature large linear magnetoresistance .125 6.5.2. Evidence for two dimensional (2D) magnetotransport .127 6.5.3. Study of weak localization 133 6.5.4. Resistance (R)-temperature (T) characteristic 136 6.6. Conclusion 137 Chapter 7. Conclusion and future work 139 ix found to exhibit efficient and fast photodetection properties. Specifically, it is observed that the number of layers in EG further influences the photocurrent magnitude and response time regardless of incident photon energy or intensity. The maximum external photoresponsivity ~ 31.3 mA W-1 at a bias voltage ~ 0.7 V under illumination with 632.8 nm wavelength is estimated. I have also developed a simple, dry, effective, economical, and environmentally safe method of mild oxygen plasma treatment in EG devices to produce high-gain ultraviolet (UV) photodetectors. An oxygen plasma treated epitaxial graphene (OPTEG) device shows high selectivity, large photoconductive gain in order of 104, and detectivity of 1.3 × 1012 Jones in the UV spectral range, and that highlight its potential advantages over Si and other semiconductor UV photodetectors. The method’s compatibility with CMOS process flow make it an efficient technique to fabricate graphene based high-gain photodetectors, as well as potential applications in UV photodetection, imaging etc. Multilayer EG on semi insulating C-face SiC substrate, which behave as electronically decoupled single sheets of graphene, shows a large (~ 50 %) linear magnetoresistance (LMR), which is stable at room temperature, distinguishing EG from other carbon materials. A two-dimensional (2D) magnetotransport effect is observed, which gives rise to LMR in EG. The LMR property observed in EG on C-face SiC suggests potential applications as magnetic sensors. Future work 1. Preparation of EG on SiC substrates still needs further optimization to produce single, or tri-layer graphene over large area on the substrate, up to 140 wafer scale. High quality EG on C-face SiC would be of much interest for magnetotransport properties such as spin injection in spin valve devices, in which high mobility EG would be a great advantage. Furthermore, asgrown EG on C-face shows the LMR properties and this material may further be explored in geometrical devices (For example, van der Pauw geometry) to improve the LMR magnitude further. 2. Although the laser patterning is a simple method to fabricate large area devices, it has limitations such as low device efficiency (~ 0.5 mA W-1) at zero-bias. The maximum photoresponsivity ~ 0.1 A W-1 is achieved with the interdigitated device at bias voltage of -10 V. This further provides a practical means to reduce the width of LEG in the device in order to produce low-power consuming and high-efficiency photodetectors. The asymmetric metallization scheme in graphene with reduced channel length in an interdigitated device structure could be interesting to explore it on wafer scale and hence leading to high perfomance photodetectors. Nevertheless, graphene can also be incorporated in highly light absorbing materials such as quantum dots (QDs), or other semiconductor materials to produce high efficiency photoconductive or photovoltaic devices. 3. To investigate the effect of thermal annealing, reduction of channel length and asymmetric metallization scheme in oxygen plasma treated epitaxial graphene devices. These strategies can be implemented with the OPTEG devices to further enhance its performance. For example, the device response time (of the order of seconds) is slower and a device with 141 narrower channel length (reducing carrier transit time) may shorten the response time. 4. Altering the electronic and optical properties of single layer/few layer graphene via oxygen plasma treatments. For example, further in-depth studies could be done to investigate adsorbed oxygen-related doping or bandgap opening, many body effects (such as electron-electron, or electronhole interactions), and 2D saddle-point excitons. Future work can also be done by varying the number of graphene layers for the photodetector studies, and more in-depth studies of the mechanisms involved (e.g. using optical ellipsometry, TEM) in OPTEG devices. 142 Bibliography 1. K. I. Bolotin, K. J. Sikes, Z. Jiang, M. Klima, G. Fudenberg, J. Hone, P. Kim and H. L. Stormer, Solid State Commun., 2008, 146, 351. 2. S. V. Morozov, K. S. Novoselov, M. I. Katsnelson, F. Schedin, D. C. Elias, J. A. Jaszczak and A. K. Geim, Phys. Rev. Lett., 2008, 100, 016602. 3. J. Hass, R. Feng, T. Li, X. Li, Z. Zong, W. A. de Heer, P. N. First, E. H. Conrad, C. A. Jeffrey and C. Berger, Appl. Phys. Lett., 2006, 89, 143106. 4. Y. B. Zhang, Y. W. Tan, H. L. Stormer and P. Kim, Nature, 2005, 438, 201. 5. K. S. Novoselov, D. Jiang, F. Schedin, T. J. Booth, V. V. Khotkevich, S. V. Morozov and A. K. Geim, P. Natl. Acad. Sci. USA, 2005, 102, 10451. 6. K. S. Novoselov, A. K. Geim, S. V. Morozov, D. Jiang, Y. Zhang, S. V. Dubonos, I. V. Grigorieva and A. A. Firsov, Science, 2004, 306, 666. 7. K. S. Novoselov, A. K. Geim, S. V. Morozov, D. Jiang, M. I. Katsnelson, I. V. Grigorieva, S. V. Dubonos and A. A. Firsov, Nature, 2005, 438, 197. 8. H. Shioyama, J. Mater. Sci. Lett., 2001, 20, 499. 9. M. Lotya, Y. Hernandez, P. J. King, R. J. Smith, V. Nicolosi, L. S. Karlsson, F. M. Blighe, S. De, Z. M. Wang, I. T. McGovern, G. S. Duesberg and J. N. Coleman, J. Am. Chem. Soc., 2009, 131, 3611. 10. Y. Hernandez, V. Nicolosi, M. Lotya, F. M. Blighe, Z. Y. Sun, S. De, I. T. McGovern, B. Holland, M. Byrne, Y. K. Gun'ko, J. J. Boland, P. Niraj, G. Duesberg, S. Krishnamurthy, R. Goodhue, J. Hutchison, V. Scardaci, A. C. Ferrari and J. N. Coleman, Nat. Nanotechnol., 2008, 3, 563. 11. S. Marchini, S. Gunther and J. Wintterlin, Phys. Rev. B, 2007, 76, 075429. 12. C. Berger, Z. M. Song, X. B. Li, X. S. Wu, N. Brown, C. Naud, D. Mayou, T. B. Li, J. Hass, A. N. Marchenkov, E. H. Conrad, P. N. First and W. A. de Heer, Science, 2006, 312, 1191. 13. T. A. Land, T. Michely, R. J. Behm, J. C. Hemminger and G. Comsa, Surf. Sci., 1992, 264, 261. 14. H. Ueta, M. Saida, C. Nakai, Y. Yamada, M. Sasaki and S. Yamamoto, Surf. Sci., 2004, 560, 183. 15. A. K. Geim and K. S. Novoselov, Nat. Mater., 2007, 6, 183. 143 16. Luxmi, S. Nie, P. J. Fisher, R. M. Feenstra, G. Gu and Y. G. Sun, J. Electron. Mater., 2009, 38, 718. 17. C. Faugeras, A. Nerriere, M. Potemski, A. Mahmood, E. Dujardin, C. Berger and W. A. de Heer, Appl. Phys. Lett., 2008, 92, 011914. 18. A. H. Castro Neto, F. Guinea, N. M. R. Peres, K. S. Novoselov and A. K. Geim, Rev. Mod. Phys., 2009, 81, 109. 19. P. R. Wallace, Phys. Rev., 1947, 71, 476. 20. J. C. Charlier, P. C. Eklund, J. Zhu and A. C. Ferrari, Top. Appl. Phys., 2008, 111, 673. 21. P. Avouris, Z. H. Chen and V. Perebeinos, Nat. Nanotechnol., 2007, 2, 605. 22. Y. B. Zhang, T. T. Tang, C. Girit, Z. Hao, M. C. Martin, A. Zettl, M. F. Crommie, Y. R. Shen and F. Wang, Nature, 2009, 459, 820. 23. Y. M. Lin and P. Avouris, Nano Lett., 2008, 8, 2119. 24. J. H. Chen, C. Jang, S. Adam, M. S. Fuhrer, E. D. Williams and M. Ishigami, Nat. Phys., 2008, 4, 377. 25. F. Schedin, A. K. Geim, S. V. Morozov, E. W. Hill, P. Blake, M. I. Katsnelson and K. S. Novoselov, Nat. Mater., 2007, 6, 652. 26. B. Seradjeh and M. Franz, Phys. Rev. Lett., 2008, 101, 246404. 27. B. Dlubak, M. B. Martin, C. Deranlot, B. Servet, S. Xavier, R. Mattana, M. Sprinkle, C. Berger, W. A. De Heer, F. Petroff, A. Anane, P. Seneor and A. Fert, Nat. Phys., 2012, 8, 557. 28. J. Hass, F. Varchon, J. E. Millan-Otoya, M. Sprinkle, N. Sharma, W. A. De Heer, C. Berger, P. N. First, L. Magaud and E. H. Conrad, Phys. Rev. Lett., 2008, 100, 125504. 29. A. B. Kuzmenko, E. van Heumen, F. Carbone and D. van der Marel, Phys. Rev. Lett., 2008, 100, 117401. 30. R. R. Nair, P. Blake, A. N. Grigorenko, K. S. Novoselov, T. J. Booth, T. Stauber, N. M. R. Peres and A. K. Geim, Science, 2008, 320, 1308. 31. C. Casiraghi, A. Hartschuh, E. Lidorikis, H. Qian, H. Harutyunyan, T. Gokus, K. S. Novoselov and A. C. Ferrari, Nano Lett., 2007, 7, 2711. 32. F. Wang, Y. B. Zhang, C. S. Tian, C. Girit, A. Zettl, M. Crommie and Y. R. Shen, Science, 2008, 320, 206. 33. K. F. Mak, C. H. Lui, J. Shan and T. F. Heinz, Phys. Rev. Lett., 2009, 102, 256405. 34. J. McClain and J. Schrier, J. Phys. Chem. C, 2010, 114, 14332. 144 35. L. Dossel, L. Gherghel, X. L. Feng and K. Mullen, Angew Chem. Int. Edit., 2011, 50, 2540. 36. T. Gokus, R. R. Nair, A. Bonetti, M. Bohmler, A. Lombardo, K. S. Novoselov, A. K. Geim, A. C. Ferrari and A. Hartschuh, ACS Nano, 2009, 3, 3963. 37. Z. T. Luo, P. M. Vora, E. J. Mele, A. T. C. Johnson and J. M. Kikkawa, Appl. Phys. Lett., 2009, 94, 111909. 38. J. V. Frangioni, Curr. Opin. Chem. Biol., 2003, 7, 626. 39. X. M. Sun, Z. Liu, K. Welsher, J. T. Robinson, A. Goodwin, S. Zaric and H. J. Dai, Nano Res., 2008, 1, 203. 40. M. I. Katsnelson, K. S. Novoselov and A. K. Geim, Nat. Phys., 2006, 2, 620. 41. E. V. Castro, K. S. Novoselov, S. V. Morozov, N. M. R. Peres, J. M. B. L. Dos Santos, J. Nilsson, F. Guinea, A. K. Geim and A. H. C. Neto, Phys. Rev. Lett., 2007, 99, 216802. 42. W. Chen, S. Chen, D. C. Qi, X. Y. Gao and A. T. S. Wee, J. Am. Chem. Soc., 2007, 129, 10418. 43. X. C. Miao, S. Tongay, M. K. Petterson, K. Berke, A. G. Rinzler, B. R. Appleton and A. F. Hebard, Nano Lett., 2012, 12, 2745. 44. Z. Y. Chen, I. Santoso, R. Wang, L. F. Xie, H. Y. Mao, H. Huang, Y. Z. Wang, X. Y. Gao, Z. K. Chen, D. G. Ma, A. T. S. Wee and W. Chen, Appl. Phys. Lett., 2010, 96, 193302. 45. D. C. Elias, R. R. Nair, T. M. G. Mohiuddin, S. V. Morozov, P. Blake, M. P. Halsall, A. C. Ferrari, D. W. Boukhvalov, M. I. Katsnelson, A. K. Geim and K. S. Novoselov, Science, 2009, 323, 610. 46. V. Abdelsayed, S. Moussa, H. M. Hassan, H. S. Aluri, M. M. Collinson and M. S. El-Shall, J. Phys. Chem. Lett., 2010, 1, 2804. 47. E. W. Hill, A. K. Geim, K. Novoselov, F. Schedin and P. Blake, IEEE T. Magn., 2006, 42, 2694. 48. N. Tombros, C. Jozsa, M. Popinciuc, H. T. Jonkman and B. J. van Wees, Nature, 2007, 448, 571. 49. W. A. de Heer, C. Berger, M. Ruan, M. Sprinkle, X. B. Li, Y. K. Hu, B. Q. Zhang, J. Hankinson and E. Conrad, P. Natl. Acad. Sci. USA, 2011, 108, 16900. 50. A. Locatelli, K. R. Knox, D. Cvetko, T. O. Mentes, M. A. Nino, S. C. Wang, M. B. Yilmaz, P. Kim, R. M. Osgood and A. Morgante, ACS Nano, 2010, 4, 4879. 51. H. B. Heersche, P. Jarillo-Herrero, J. B. Oostinga, L. M. K. Vandersypen and A. F. Morpurgo, Nature, 2007, 446, 56. 145 52. X. Q. Liu, R. Aizen, R. Freeman, O. Yehezkeli and I. Willner, ACS Nano, 2012, 6, 3553. 53. L. M. Zhu, L. Q. Luo and Z. X. Wang, Biosens. Bioelectron., 2012, 35, 507. 54. B. M. Venkatesan, D. Estrada, S. Banerjee, X. Z. Jin, V. E. Dorgan, M. H. Bae, N. R. Aluru, E. Pop and R. Bashir, ACS Nano, 2012, 6, 441. 55. P. K. Ang, A. Li, M. Jaiswal, Y. Wang, H. W. Hou, J. T. L. Thong, C. T. Lim and K. P. Loh, Nano Lett., 2011, 11, 5240. 56. S. Mao, K. H. Yu, G. H. Lu and J. H. Chen, Nano Res., 2011, 4, 921. 57. S. Gilje, S. Han, M. Wang, K. L. Wang and R. B. Kaner, Nano Lett., 2007, 7, 3394. 58. X. Wang, L. J. Zhi and K. Mullen, Nano Lett., 2008, 8, 323. 59. S. Bae, H. Kim, Y. Lee, X. F. Xu, J. S. Park, Y. Zheng, J. Balakrishnan, T. Lei, H. R. Kim, Y. I. Song, Y. J. Kim, K. S. Kim, B. Ozyilmaz, J. H. Ahn, B. H. Hong and S. Iijima, Nat. Nanotechnol., 2010, 5, 574. 60. T. T. Feng, D. Xie, Y. X. Lin, Y. Y. Zang, T. L. Ren, R. Song, H. M. Zhao, H. Tian, X. Li, H. W. Zhu and L. T. Liu, Appl. Phys. Lett., 2011, 99, 132904. 61. G. F. Fan, H. W. Zhu, K. L. Wang, J. Q. Wei, X. M. Li, Q. K. Shu, N. Guo and D. H. Wu, ACS Appl. Mater. Inter., 2011, 3, 721. 62. C. Xie, J. S. Jie, B. A. Nie, T. X. Yan, Q. Li, P. Lv, F. Z. Li, M. Z. Wang, C. Y. Wu, L. Wang and L. B. Luo, Appl. Phys. Lett., 2012, 100, 193103. 63. X. W. Fu, Z. M. Liao, Y. B. Zhou, H. C. Wu, Y. Q. Bie, J. Xu and D. P. Yu, Appl. Phys. Lett., 2012, 100, 223114. 64. H. X. Chang, Z. H. Sun, K. Y. F. Ho, X. M. Tao, F. Yan, W. M. Kwok and Z. J. Zheng, Nanoscale, 2011, 3, 258. 65. H. Lee, K. Heo, J. Park, Y. Park, S. Noh, K. S. Kim, C. Lee, B. H. Hong, J. Jian and S. Hong, Journal of Materials Chemistry, 2012, 22, 8372. 66. H. Y. Yang, D. I. Son, T. W. Kim, J. M. Lee and W. I. Park, Org. Electron., 2010, 11, 1313. 67. G. Konstantatos, M. Badioli, L. Gaudreau, J. Osmond, M. Bernechea, F. P. G. de Arquer, F. Gatti and F. H. L. Koppens, Nat. Nanotechnol., 2012, 7, 363. 68. K. K. Manga, S. Wang, M. Jaiswal, Q. L. Bao and K. P. Loh, Adv. Mater., 2010, 22, 5265. 69. F. N. Xia, T. Mueller, Y. M. Lin, A. Valdes-Garcia and P. Avouris, Nat. Nanotechnol., 2009, 4, 839. 146 70. P. A. George, J. Strait, J. Dawlaty, S. Shivaraman, M. Chandrashekhar, F. Rana and M. G. Spencer, Nano Lett., 2008, 8, 4248. 71. J. M. Dawlaty, S. Shivaraman, M. Chandrashekhar, F. Rana and M. G. Spencer, Appl. Phys. Lett., 2008, 92, 042116. 72. A. N. Cao, Z. Liu, S. S. Chu, M. H. Wu, Z. M. Ye, Z. W. Cai, Y. L. Chang, S. F. Wang, Q. H. Gong and Y. F. Liu, Adv. Mater., 2010, 22, 103. 73. B. E. A. T. Saleh, M. C. Fundamentals of Photonics Ch. 18, 784-803 (Willey, 2007). 74. A. R. Wright, J. C. Cao and C. Zhang, Phys. Rev. Lett., 2009, 103. 75. Z. P. Sun, T. Hasan, F. Torrisi, D. Popa, G. Privitera, F. Q. Wang, F. Bonaccorso, D. M. Basko and A. C. Ferrari, ACS Nano, 2010, 4, 803. 76. T. Mueller, F. N. A. Xia and P. Avouris, Nat. Photonics, 2010, 4, 297. 77. C. S. Lin, R. H. Yeh, C. H. Liao and J. W. Hong, Solid State Electron., 2002, 46, 2027. 78. H. C. Luan, K. Wada, L. C. Kimerling, G. Masini, L. Colace and G. Assanto, Opt. Mater., 2001, 17, 71. 79. C. Berger, Z. M. Song, T. B. Li, X. B. Li, A. Y. Ogbazghi, R. Feng, Z. T. Dai, A. N. Marchenkov, E. H. Conrad, P. N. First and W. A. de Heer, J. Phys. Chem. B, 2004, 108, 19912. 80. Y. Takahashi, Y. Ono, A. Fujiwara and H. Inokawa, J. Phys.-Condens. Mat., 2002, 14, R995. 81. X. Z. Zhou, G. Lu, X. Y. Qi, S. X. Wu, H. Li, F. Boey and H. Zhang, J. Phys. Chem. C, 2009, 113, 19119. 82. D. Li, M. B. Muller, S. Gilje, R. B. Kaner and G. G. Wallace, Nat. Nanotechnol., 2008, 3, 101. 83. X. Huang, X. Y. Qi, F. Boey and H. Zhang, Chem. Soc. Rev., 2012, 41, 666. 84. A. Abouimrane, O. C. Compton, K. Amine and S. T. Nguyen, J. Phys. Chem. C, 2010, 114, 12800. 85. P. C. Lian, X. F. Zhu, H. F. Xiang, Z. Li, W. S. Yang and H. H. Wang, Electrochim. Acta, 2010, 56, 834. 86. D. Y. Pan, S. Wang, B. Zhao, M. H. Wu, H. J. Zhang, Y. Wang and Z. Jiao, Chem. Mater., 2009, 21, 3136. 87. C. Y. Wang, D. Li, C. O. Too and G. G. Wallace, Chem. Mater., 2009, 21, 2604. 88. G. X. Wang, X. P. Shen, J. Yao and J. Park, Carbon, 2009, 47, 2049. 89. Z. M. Ao and F. M. Peeters, Phys. Rev. B, 2010, 81, 205406. 147 90. C. Ataca, E. Akturk, S. Ciraci and H. Ustunel, Appl. Phys. Lett., 2008, 93, 043123. 91. Y. Chan and J. M. Hill, Nanotechnology, 2011, 22, 305403. 92. V. Tozzini and V. Pellegrini, J. Phys. Chem. C, 2011, 115, 25523. 93. B. H. Kim, W. G. Hong, H. Y. Yu, Y. K. Han, S. M. Lee, S. J. Chang, H. R. Moon, Y. Jun and H. J. Kim, Phys. Chem. Chem. Phys., 2012, 14, 1480. 94. G. Binnig, H. Rohrer, C. Gerber and E. Weibel, Appl. Phys. Lett., 1982, 40, 178. 95. M. F. Crommie, C. P. Lutz and D. M. Eigler, Science, 1993, 262, 218. 96. V. W. Brar, Y. Zhang, Y. Yayon, T. Ohta, J. L. McChesney, A. Bostwick, E. Rotenberg, K. Horn and M. F. Crommie, Appl. Phys. Lett., 2007, 91, 122102. 97. F. J. Giessibl, Rev. Mod. Phys., 2003, 75, 949. 98. N. A. Geisse, Mater. Today, 2009, 12, 40. 99. http://www.andor.com/learn/applications/?docID=64. 100. http://www.chm.bris.ac.uk/pt/diamond/stuthesis/chapter2.htm. 101. A. C. Ferrari, Solid State Commun., 2007, 143, 47. 102. D. Graf, F. Molitor, K. Ensslin, C. Stampfer, A. Jungen, C. Hierold and L. Wirtz, Nano Lett., 2007, 7, 238. 103. D. S. Lee, C. Riedl, B. Krauss, K. von Klitzing, U. Starke and J. H. Smet, Nano Lett., 2008, 8, 4320. 104. P. Lespade, R. Aljishi and M. S. Dresselhaus, Carbon, 1982, 20, 427. 105. P. Lespade, A. Marchand, M. Couzi and F. Cruege, Carbon, 1984, 22, 375. 106. Z. H. Ni, W. Chen, X. F. Fan, J. L. Kuo, T. Yu, A. T. S. Wee and Z. X. Shen, Phys. Rev. B, 2008, 77, 115416. 107. Z. H. Ni, H. M. Fan, Y. P. Feng, Z. X. Shen, B. J. Yang and Y. H. Wu, J. Chem. Phys., 2006, 124, 204703. 108. H. Wilhelm, M. Lelaurain, E. McRae and B. Humbert, J. Appl. Phys., 1998, 84, 6552. 109. M. A. Pimenta, G. Dresselhaus, M. S. Dresselhaus, L. G. Cancado, A. Jorio and R. Saito, Phys. Chem. Chem. Phys., 2007, 9, 1276. 110. R. Saito, A. Jorio, A. G. Souza, G. Dresselhaus, M. S. Dresselhaus and M. A. Pimenta, Phys. Rev. Lett., 2002, 88, 027401. 111. C. Thomsen and S. Reich, Phys. Rev. Lett., 2000, 85, 5214. 112. W. Kohn, Phys. Rev. Lett., 1959, 2, 393. 113. S. Piscanec, M. Lazzeri, F. Mauri, A. C. Ferrari and J. Robertson, Phys. Rev. Lett., 2004, 93, 185503. 148 114. R. Sevak Singh, V. Nalla, W. Chen, W. Ji and A. T. S. Wee, Appl. Phys. Lett., 2012, 100, 093116. 115. R. S. Singh, V. Nalla, W. Chen, A. T. S. Wee and W. Ji, ACS Nano, 2011, 5, 5969. 116. J. A. Robinson, M. Wetherington, J. L. Tedesco, P. M. Campbell, X. Weng, J. Stitt, M. A. Fanton, E. Frantz, D. Snyder, B. L. VanMil, G. G. Jernigan, R. L. Myers-Ward, C. R. Eddy and D. K. Gaskill, Nano Lett., 2009, 9, 2873. 117. http://www.mrl.ucsb.edu/mrl/centralfacilities/chemistry/resPPMS.pdf. 118. http://www.qdusa.com/products/ppms.html. 119. P. N. First, W. A. de Heer, T. Seyller, C. Berger, J. A. Stroscio and J. S. Moon, Mrs Bull., 2010, 35, 296. 120. Y. M. Lin, C. Dimitrakopoulos, K. A. Jenkins, D. B. Farmer, H. Y. Chiu, A. Grill and P. Avouris, Science, 2010, 327, 662. 121. A. A. Lebedev, A. M. Strel'chuk, D. V. Shamshur, G. A. Oganesyan, S. P. Lebedev, M. G. Mynbaeva and A. V. Sadokhin, Semiconductors, 2010, 44, 1389. 122. A. Charrier, A. Coati, T. Argunova, F. Thibaudau, Y. Garreau, R. Pinchaux, I. Forbeaux, J. M. Debever, M. Sauvage-Simkin and J. M. Themlin, J. Appl. Phys., 2002, 92, 2479. 123. S. W. Poon, W. Chen, E. S. Tok and A. T. S. Wee, Appl. Phys. Lett., 2008, 92, 104102. 124. A. Das, S. Pisana, B. Chakraborty, S. Piscanec, S. K. Saha, U. V. Waghmare, K. S. Novoselov, H. R. Krishnamurthy, A. K. Geim, A. C. Ferrari and A. K. Sood, Nat. Nanotechnol., 2008, 3, 210. 125. N. Ferralis, R. Maboudian and C. Carraro, Phys. Rev. Lett., 2008, 101, 156801. 126. D. Z. Feng, S. R. Liao, P. Dong, N. N. Feng, H. Liang, D. W. Zheng, C. C. Kung, J. Fong, R. Shafiiha, J. Cunningham, A. V. Krishnamoorthy and M. Asghari, Appl. Phys. Lett., 2009, 95, 261105. 127. A. Ghasempour Ardakani, M. Pazoki, S. M. Mahdavi, A. R. Bahrampour and N. Taghavinia, Appl. Surf. Sci., 2012, 258, 5405. 128. A. Muller, G. Konstantinidis, M. Androulidaki, A. Dinescu, A. Stefanescu, A. Cismaru, D. Neculoiu, E. Pavelescu and A. Stavrinidis, Thin Solid Films, 2012, 520, 2158. 129. M. Currie, F. Quaranta, A. Cola, E. M. Gallo and B. Nabet, Appl Phys Lett, 2011, 99. 130. Y. Liang, H. Liang, X. Xiao and S. Hark, Journal of Materials Chemistry, 2012, 22, 1199. 149 131. A. K. Geim, Science, 2009, 324, 1530. 132. 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 and K. S. Novoselov, Nano Lett., 2008, 8, 1704. 133. Z. Q. Li, E. A. Henriksen, Z. Jiang, Z. Hao, M. C. Martin, P. Kim, H. L. Stormer and D. N. Basov, Nat. Phys., 2008, 4, 532. 134. T. Winzer, A. Knorr and E. Malic, Nano Lett., 2010, 10, 4839. 135. F. N. Xia, T. Mueller, Y. M. Lin and P. Avouris, 2010 Conference on Lasers and Electro-Optics (Cleo) and Quantum Electronics and Laser Science Conference (Qels), 2010. 136. B. Chitara, S. B. Krupanidhi and C. N. R. Rao, Appl.Phys. Lett., 2011, 99, 113114. 137. B. Chitara, L. S. Panchakarla, S. B. Krupanidhi and C. N. R. Rao, Adv. Mater., 2011, 23, 5419. 138. T. Mueller, F. Xia, M. Freitag, J. Tsang and P. Avouris, Phys Rev B, 2009, 79. 139. S. Wang, Q. S. Zeng, L. J. Yang, Z. Y. Zhang, Z. X. Wang, T. A. Pei, L. Ding, X. L. Liang, M. Gao, Y. Li and L. M. Peng, Nano Lett., 2011, 11, 23. 140. H. T. Liu, S. M. Ryu, Z. Y. Chen, M. L. Steigerwald, C. Nuckolls and L. E. Brus, J. Am. Chem. Soc., 2009, 131, 17099. 141. S. Ryu, L. Liu, S. Berciaud, Y. J. Yu, H. T. Liu, P. Kim, G. W. Flynn and L. E. Brus, Nano Lett., 2010, 10, 4944. 142. Y. L. Zhang, L. Guo, S. Wei, Y. Y. He, H. Xia, Q. D. Chen, H. B. Sun and F. S. Xiao, Nano Today, 2010, 5, 15. 143. D. A. Sokolov, K. R. Shepperd and T. M. Orlando, J. Phys. Chem. Lett., 2010, 1, 2633. 144. X. S. Wu, M. Sprinkle, X. B. Li, F. Ming, C. Berger and W. A. de Heer, Phys. Rev. Lett., 2008, 101, 026801. 145. K. N. Kudin, B. Ozbas, H. C. Schniepp, R. K. Prud'homme, I. A. Aksay and R. Car, Nano Lett., 2008, 8, 36. 146. D. Yang, A. Velamakanni, G. Bozoklu, S. Park, M. Stoller, R. D. Piner, S. Stankovich, I. Jung, D. A. Field, C. A. Ventrice and R. S. Ruoff, Carbon, 2009, 47, 145. 147. N. Wang, B. D. Yao, Y. F. Chan and X. Y. Zhang, Nano Lett., 2003, 3, 475. 148. L. Liu, S. M. Ryu, M. R. Tomasik, E. Stolyarova, N. Jung, M. S. Hybertsen, M. L. Steigerwald, L. E. Brus and G. W. Flynn, Nano Lett., 2008, 8, 1965. 150 149. S. Ryu, M. Y. Han, J. Maultzsch, T. F. Heinz, P. Kim, M. L. Steigerwald and L. E. Brus, Nano Lett., 2008, 8, 4597. 150. F. N. Xia, T. Mueller, R. Golizadeh-Mojarad, M. Freitag, Y. M. Lin, J. Tsang, V. Perebeinos and P. Avouris, Nano Lett., 2009, 9, 1039. 151. E. G. Mishchenko, Phys. Rev. Lett., 2009, 103, 246802. 152. X. D. Xu, N. M. Gabor, J. S. Alden, A. M. van der Zande and P. L. McEuen, Nano Lett., 2010, 10, 562. 153. G. C. Xing, H. C. Guo, X. H. Zhang, T. C. Sum and C. H. A. Huan, Opt. Express, 2010, 18, 4564. 154. K. Berndt, H. Durr and D. Palme, Opt. Commun., 1983, 47, 321. 155. D. M. Rayner, A. E. Mckinnon, A. G. Szabo and P. A. Hackett, Can. J. Chem., 1976, 54, 3246. 156. S. M. N. Sze, K. K. Physics of Semiconductor Devices, 3rd and I. N. Y. ed.; John Wiley & Sons, 2007. 157. N. Toyama, J. Appl. Phys., 1988, 64, 2515. 158. M. S. Arnold, J. D. Zimmerman, C. K. Renshaw, X. Xu, R. R. Lunt, C. M. Austin and S. R. Forrest, Nano Lett., 2009, 9, 3354. 159. M. Freitag, Y. Martin, J. A. Misewich, R. Martel and P. H. Avouris, Nano Lett., 2003, 3, 1067. 160. X. Lv, Y. Huang, Z. B. Liu, J. G. Tian, Y. Wang, Y. F. Ma, J. J. Liang, S. P. Fu, X. J. Wan and Y. S. Chen, Small, 2009, 5, 1682. 161. H. B. Michaelson, J. Appl. Phys., 1977, 48, 4729. 162. D. M. Rayner, A. E. Mckinnon and A. G. Szabo, Rev. Sci. Instrum., 1977, 48, 1050. 163. D. A. Dikin, S. Stankovich, E. J. Zimney, R. D. Piner, G. H. B. Dommett, G. Evmenenko, S. T. Nguyen and R. S. Ruoff, Nature, 2007, 448, 457. 164. S. Park, N. Mohanty, J. W. Suk, A. Nagaraja, J. H. An, R. D. Piner, W. W. Cai, D. R. Dreyer, V. Berry and R. S. Ruoff, Adv. Mater., 2010, 22, 1736. 165. H. A. Becerril, J. Mao, Z. Liu, R. M. Stoltenberg, Z. Bao and Y. Chen, ACS Nano, 2008, 2, 463. 166. A. Bagri, C. Mattevi, M. Acik, Y. J. Chabal, M. Chhowalla and V. B. Shenoy, Nat. Chem., 2010, 2, 581. 167. J. B. Zhang, N. Xi, K. W. C. Lai, H. Z. Chen, Y. L. Luo and G. Y. Li, 2007 7th IEEE Conference on Nanotechnology, Vol 1-3, 2007, 1164. 168. S. Liu, J. Ye, Y. Cao, Q. Shen, Z. Liu, L. Qi and X. Guo, Small, 2009, 5, 2371. 151 169. Y. Lin, K. Zhang, W. F. Chen, Y. D. Liu, Z. G. Geng, J. Zeng, N. Pan, L. F. Yan, X. P. Wang and J. G. Hou, ACS Nano, 2010, 4, 3033. 170. X. M. Geng, L. Niu, Z. Y. Xing, R. S. Song, G. T. Liu, M. T. Sun, G. S. Cheng, H. J. Zhong, Z. H. Liu, Z. J. Zhang, L. F. Sun, H. X. Xu, L. Lu and L. W. Liu, Adv. Mater., 2010, 22, 638. 171. G. Kalita, S. Adhikari, H. R. Aryal, M. Umeno, R. Afre, T. Soga and M. Sharon, Appl. Phys. Lett., 2008, 92, 063508. 172. T. Sugino, D. Hirata, I. Yamamura, K. Matsuda and J. Shirafuji, J. Electron. Mater., 1996, 25, 733. 173. U. Cvelbar, B. Markoli, I. Poberaj, A. Zalar, L. Kosec and S. Spaic, Appl. Surf. Sci., 2006, 253, 1861. 174. N. Xiao, X. C. Dong, L. Song, D. Y. Liu, Y. Tay, S. X. Wu, L. J. Li, Y. Zhao, T. Yu, H. Zhang, W. Huang, H. H. Hng, P. M. Ajayan and Q. Y. Yan, ACS Nano, 2011, 5, 2749. 175. C. Soci, A. Zhang, B. Xiang, S. A. Dayeh, D. P. R. Aplin, J. Park, X. Y. Bao, Y. H. Lo and D. Wang, Nano Lett., 2007, 7, 1003. 176. A. Bera and D. Basak, Appl. Phys. Lett., 2008, 93, 053102. 177. H. Y. Jeong, J. Y. Kim, J. W. Kim, J. O. Hwang, J. E. Kim, J. Y. Lee, T. H. Yoon, B. J. Cho, S. O. Kim, R. S. Ruoff and S. Y. Choi, Nano Lett., 2010, 10, 4381. 178. Z. Q. Luo, J. Z. Shang, S. H. Lim, D. H. Li, Q. H. Xiong, Z. X. Shen, J. Y. Lin and T. Yu, Appl. Phys. Lett., 2010, 97, 233111. 179. D. J. Bishop, D. C. Tsui and R. C. Dynes, Phys. Rev. Lett., 1980, 44, 1153. 180. G. J. Dolan and D. D. Osheroff, Phys. Rev. Lett., 1979, 43, 721. 181. D. J. Thouless, Phys. Rev. Lett., 1977, 39, 1167. 182. E. McCann, K. Kechedzhi, V. I. Fal'ko, H. Suzuura, T. Ando and B. L. Altshuler, Phys. Rev. Lett., 2006, 97, 146805. 183. B. L. Altshuler, A. G. Aronov and P. A. Lee, Phys. Rev. Lett., 1980, 44, 1288. 184. X. S. Wu, X. B. Li, Z. M. Song, C. Berger and W. A. de Heer, Phys. Rev. Lett., 2007, 98, 136801. 185. P. A. N. V. Joshi, Science, and Technology ( Marcel Dekker, New Yark, 1990). 186. K. W. Liu, M. Sakurai and M. Aono, Sensors-Basel, 2010, 10, 8604. 187. A. Behnam, J. Johnson, Y. Choi, L. Noriega, M. G. Ertosun, Z. C. Wu, A. G. Rinzler, P. Kapur, K. C. Saraswat and A. Ural, J. Appl. Phys., 2008, 103, 114315. 188. H. L. Xue, X. Z. Kong, Z. R. Liu, C. X. Liu, J. R. Zhou, W. Y. Chen, S. P. Ruan and Q. Xu, Appl. Phys. Lett., 2007, 90, 201118. 152 189. Y. Liu, C. R. Gorla, S. Liang, N. Emanetoglu, Y. Lu, H. Shen and M. Wraback, J Electron Mater., 2000, 29, 69. 190. H. Ohta, M. Hirano, K. Nakahara, H. Maruta, T. Tanabe, M. Kamiya, T. Kamiya and H. Hosono, Appl. Phys. Lett., 2003, 83, 1029. 191. I. S. Jeong, J. H. Kim and S. Im, Appl. Phys. Lett., 2003, 83, 2946. 192. M. Martens, J. Schlegel, P. Vogt, F. Brunner, R. Lossy, J. Wurfl, M. Weyers and M. Kneissl, Appl. Phys. Lett., 2011, 98, 211114. 193. M. Sofos, J. Goldberger, D. A. Stone, J. E. Allen, Q. Ma, D. J. Herman, W. W. Tsai, L. J. Lauhon and S. I. Stupp, Nat. Mater., 2009, 8, 68. 194. http://www.eoc-inc.com/UV_detectors_silicon_carbide_photodiodes.htm. 195. http://www.eoc-inc.com/ifw/JEP%205-365%200408.pdf. 196. C. K. Wang, S. J. Chang, Y. K. Su, Y. Z. Chiou, C. S. Chang, T. K. Lin, H. L. Liu and J. J. Tang, Semicond. Sci. Tech., 2005, 20, 485. 197. Y. Yamamoto, T. Fukushima, Y. Suna, N. Ishii, A. Saeki, S. Seki, S. Tagawa, M. Taniguchi, T. Kawai and T. Aida, Science, 2006, 314, 1761. 198. G. Mazzeo, J. L. Reverchon, J. Y. Duboz and A. Dussaigne, IEEE Sens. J., 2006, 6, 957. 199. I. Rodionov, J. M. Bidault, I. Crotty, P. Fonte, F. Galy, V. Peskov and O. Zanette, in 2005 IEEE Nuclear Science Symposium Conference Record, Vols 1-5, ed. B. Yu, 2005, 3045. 200. J. Hass, W. A. de Heer and E. H. Conrad, J. Phys.-Condens. Mat., 2008, 20, 323202. 201. J. Hass, R. Feng, J. E. Millan-Otoya, X. Li, M. Sprinkle, P. N. First, W. A. de Heer, E. H. Conrad and C. Berger, Phys. Rev. B, 2007, 75, 214109. 202. F. Varchon, P. Mallet, J. Y. Veuillen and L. Magaud, Phys. Rev. B, 2008, 77, 165415. 203. T. Ohta, A. Bostwick, J. L. McChesney, T. Seyller, K. Horn and E. Rotenberg, Phys. Rev. Lett., 2007, 98, 206802. 204. S. Latil, V. Meunier and L. Henrard, Phys. Rev. B, 2007, 76, 201402(R). 205. M. Sprinkle, D. Siegel, Y. Hu, J. Hicks, A. Tejeda, A. Taleb-Ibrahimi, P. Le Fevre, F. Bertran, S. Vizzini, H. Enriquez, S. Chiang, P. Soukiassian, C. Berger, W. A. de Heer, A. Lanzara and E. H. Conrad, Phys. Rev. Lett., 2009, 103, 226803. 206. D. L. Miller, K. D. Kubista, G. M. Rutter, M. Ruan, W. A. de Heer, P. N. First and J. A. Stroscio, Science, 2009, 324, 924. 153 207. Y. Kopelevich, J. H. S. Torres, R. R. da Silva, F. Mrowka, H. Kempa and P. Esquinazi, Phys. Rev. Lett., 2003, 90, 156402. 208. Y. F. Chen, M. H. Bae, C. Chialvo, T. Dirks, A. Bezryadin and N. Mason, Journal of physics. Condensed matter : an Institute of Physics journal, 2010, 22, 205301. 209. J. S. Hu and T. F. Rosenbaum, Nat. Mater., 2008, 7, 697. 210. J. H. Ngai, Y. Segal, D. Su, Y. Zhu, F. J. Walker, S. Ismail-Beigi, K. Le Hur and C. H. Ahn., Phys. Rev. B, 2010, 81, 241307. 211. T. Ando, A. B. Fowler and F. Stern, Rev. Mod. Phys., 1982, 54, 437. 212. Z. M. Liao, H. C. Wu, S. Kumar, G. S. Duesberg, Y. B. Zhou, G. L. W. Cross, I. V. Shvets and D. P. Yu, Adv. Mater., 2012, 24, 1862. 213. E. T. i. M. I. J. L. Olsen, New York, 1962). 214. W. R. Branford, A. Husmann, S. A. Solin, S. K. Clowes, T. Zhang, Y. V. Bugoslavsky and L. F. Cohen, Appl. Phys. Lett., 2005, 86, 202116. 215. A. Husmann, J. B. Betts, G. S. Boebinger, A. Migliori, T. F. Rosenbaum and M. L. Saboungi, Nature, 2002, 417, 421. 216. A. Patane, W. H. M. Feu, O. Makarovsky, O. Drachenko, L. Eaves, A. Krier, Q. D. Zhuang, M. Helm, M. Goiran and G. Hill, Phys. Rev. B, 2009, 80, 115207. 217. H. Xu, J. Lu, Y. Xia, J. Yin and Z. Liu, Solid State Commun., 2012, 152, 1150. 218. P. P. Freitas, R. Ferreira, S. Cardoso and F. Cardoso, J. Phys.-Condens. Mat., 2007, 19, 165221. 219. X. Zhang, Q. Z. Xue and D. D. Zhu, Phys. Lett. A, 2004, 320, 471. 220. Y. F. Chen, M. H. Bae, C. Chialvo, T. Dirks, A. Bezryadin and N. Mason, J. Phys.-Condens. Mat., 2010, 22, 205301. 221. B. Li, C. Y. Kao, J. W. Yoo, V. N. Prigodin and A. J. Epstein, Adv. Mater., 2011, 23, 3382. 222. N. P. Raju, V. N. Prigodin, K. I. Pokhodnya, J. S. Miller and A. J. Epstein, Synthetic Met., 2010, 160, 307. 223. H. G. Johnson, S. P. Bennett, R. Barua, L. H. Lewis and D. Heiman, Phys. Rev. B, 2010, 82, 085202. 224. T. J. McArdle, J. O. Chu, Y. Zhu, Z. H. Liu, M. Krishnan, C. M. Breslin, C. Dimitrakopoulos, R. Wisnieff and A. Grill, Appl. Phys. Lett., 2011, 98, 132108. 225. T. A. Len, L. Y. Matzui, I. V. Ovsienko, Y. I. Prylutskyy, V. V. Andrievskii, I. B. Berkutov, G. E. Grechnev and Y. A. Kolesnichenko, Low Temp. Phys., 2011, 37, 819. 154 226. Y. Oshima, T. Takenobu, K. Yanagi, Y. Miyata, H. Kataura, K. Hata, Y. Iwasa and H. Nojiri, Phys. Rev. Lett., 2010, 104, 168803. 227. R. Mahendiran, A. K. Raychaudhuri, A. Chainani and D. D. Sarma, Rev. Sci. Instrum., 1995, 66, 3071. 228. J. W. Bai, R. Cheng, F. X. Xiu, L. Liao, M. S. Wang, A. Shailos, K. L. Wang, Y. Huang and X. F. Duan, Nat. Nanotechnol., 2010, 5, 655. 229. K. Eto, Z. Ren, A. A. Taskin, K. Segawa and Y. Ando, Phys .Rev. B, 2010, 81, 195309. 230. A. A. Abrikosov, Phys. Rev. B, 1998, 58, 2788. 231. P. N. Argyres and E. N. Adams, Phys. Rev., 1956, 104, 900. 232. R. T. Bate, R. K. Willardson and A. C. Beer, J. Phys. Chem. Solids, 1959, 9, 119. 233. T. J. Diesel and W. F. Love, Phys. Rev., 1961, 124, 666. 234. J. W. Mcclure and W. J. Spry, Phys. Rev., 1968, 165, 809. 235. H. Tang, D. Liang, R. L. J. Qiu and X. P. A. Gao, ACS Nano, 2011, 5, 7510. 236. M. M. Parish and P. B. Littlewood, Nature, 2003, 426, 162. 237. V. I. Falko, J. Phys.-Condens. Mat., 1990, 2, 3797. 238. S. V. Morozov, K. S. Novoselov, M. I. Katsnelson, F. Schedin, L. A. Ponomarenko, D. Jiang and A. K. Geim, Phys. Rev. Lett., 2006, 97, 016801. 239. W. R. Anderson, D. R. Lombardi, R. G. Wheeler and T. P. Ma, IEEE Electr. Device. L., 1993, 14, 351. 240. G. Bergmann, Int. J. Mod. Phys. B, 2010, 24, 2015. 241. T. E. R. o. M. a. A. C. U. P. P L Rossiter, Cambridge, 1987). 242. G. Bergmann, Phys. Rev. B, 1983, 28, 2914. 243. R. S. Markiewicz and L. A. Harris, Phys. Rev. Lett., 1981, 46, 1149. 244. Z. Ovadyahu and Y. Imry, Phys. Rev. B, 1981, 24, 7439. 245. P. A. Lee and T. V. Ramakrishnan, Rev. Mod. Phys., 1985, 57, 287. 155 [...]... surfaces and requires transferring of graphene onto a desired substrate 1.2 Properties of graphene 1.2.1 Crystal and electronic structures Graphene comprises a single or few layers of carbon tightly packed into a hexagonal honeycomb lattice.6 Depending on the number of carbon layers graphene has various names: single layer graphene (SLG), bilayer graphene (BLG) 2 and few layer graphene (FLG) and multilayer... molecular plane and hybridizes to form π (valence band) and π* (conduction band) bands The bands form conical valleys that touch at two of high-symmetry points, conventionally labeled K and K’ called Dirac points, in the Brillouin zone As such, graphene has zero energy bandgap, and hence called semimetal Thus, the E-k relation is linear at low energies near the zero effective mass for electrons and holes.19,... strengthening of G-band and D-band in LEG, as compared to them in EG (b) Gaussian fit to the G-band in LEG to reveal two SiC peaks and a G-peak of graphene (c) Gaussian fit to the D-band in LEG to reveal a SiC peak (green) and a D-peak (blue) of graphene Both Raman analyses and non-linear I-V characteristics xv (Figure 4.8) suggest that LEG exhibits characteristics similar to reduced graphene oxide ... interesting because it shows some properties different from those observed in single layer graphene Unlike the linear energy band structure of single layer graphene, bilayer graphene has a parabolic energy band structure.18 A gap can open between the conduction band and valence band.22 BLG has been proven to be less noisy for devices. 23 3 FLG FLG consists of more than two layers (≤ 6 layers) of carbon stacked... devices such as light emitting diodes (LEDs) Zero-gap graphene lacks photoluminescence property Therefore, bandgap opening or defect incorporation to graphene would be of much interest for these devices and several potential optoelectronic devices where interband transitions play an important role One route to opening the band gap is cutting the graphene into ribbons or quantum dots Another route involves... Zero-gap graphene is not suitable for applications in switching devices or in optoelectronics Adsorption of gases such as hydrogen, oxygen on graphene surface has resulted in opening of a bandgap45 or alteration of its optical properties.36 Laser induced heating was used to reduce graphene oxide into graphene. 46 1.3.1 Spin-valve devices Spin-valve devices represent another route for possible graphene. .. ordering in graphene can be complex The subband structure of a trilayer with Bernal stacking includes two touching parabolic bands, and one with Dirac dispersion, combining the features of bilayer and monolayer graphene A gap can open in a stack with Bernal ordering and four layers if the electronic charge at the two surface layers is different from that the two inner ones.18 No gap is observed in graphene. .. processable graphene is needed to allow integration of devices over wafer scales As such, photodetector research on large area graphene7 9, 80 would be of much interest The reported low efficiency (6.1 mA W-1) could be due to the absorption by only a single layer of graphene, and the use of FLG or MLG with high mobility graphene should further improve the performance To commercialize graphene based devices, ... timeconsuming and not suitable for practical applications because of its small size.15 The second method involves epitaxial growth of graphene on substrate and is the first approach towards large area graphene growth Due to large defect densities, the sample quality is generally inferior and needs to be improved.16, 17 The chemical vapour deposition has become the most used method to grow graphene on... observed that graphene becomes metallic with increasing number of layers due to a gradual increase of charge carrier concentration at zero energy and they appear as electron-like or hole-like carriers An inhomogeneous charge distribution between layers lead to 2D electrons and holes that occupy a few graphene layers near the surface, and affect the transport properties of graphene stacks The graphene layers . the G-band in LEG to reveal two SiC peaks and a G-peak of graphene. (c) Gaussian fit to the D-band in LEG to reveal a SiC peak (green) and a D-peak (blue) of graphene. Both Raman analyses and. Materials and devices fabrication 51 3.4.2. Hall measurements 52 3.4.3. Results and discussion 53 3.5. Conclusion 55 Chapter 4. Photoconductive devices based on pristine and laser modified epitaxial. EPITAXIAL GRAPHENE: SYNTHESIS, CHARACTERIZATION, AND DEVICES RAM SEVAK SINGH (M.Tech., IIT Kharagpur)