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SiC surface orientation and Si loss rate effects on epitaxial graphene

Moonkyung Kim1, Jeonghyun Hwang1, Virgil B Shields1, Sandip Tiwari1, Michael G Spencer1* and Jo-Won Lee2*

Author Affiliations

1 School of Electrical and Computer Engineering, Cornell University, 410 Thurston Avenue, Ithaca, NY 14850-2488, USA

2 Department of Convergence Nanoscience, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul, 133-791, South Korea

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Nanoscale Research Letters 2012, 7:186  doi:10.1186/1556-276X-7-186

Published: 12 March 2012


We have explored the properties of SiC-based epitaxial graphene grown in a cold wall UHV chamber. The effects of the SiC surface orientation and silicon loss rate were investigated by comparing the characteristics of each formed graphene. Graphene was grown by thermal decomposition on both the silicon (0001) and carbon (000-1) faces of on-axis semi-insulating 6H-SiC with a "face-down" and "face-up" orientations. The thermal gradient, in relation to the silicon flux from the surface, was towards the surface and away from the surface, respectively, in the two configurations. Raman results indicate the disorder characteristics represented by ID/IG down to < 0.02 in Si-face samples and < 0.05 in C-faces over the 1 cm2 wafer surface grown at 1,450°C. AFM examination shows a better morphology in face-down surfaces. This study suggests that the optimum configuration slows the thermal decomposition and allows the graphene to form near the equilibrium. The Si-face-down orientation (in opposition to the temperature gradient) results in a better combination of low disorder ratio, ID/IG, and smooth surface morphology. Mobility of Si-face-down orientation has been measured as high as approximately 1,500 cm2/Vs at room temperature. Additionally, the field effect transistors have been fabricated on both Si-face-down and C-face-down showing an ambipolar behavior with more favorable electron conduction.