Raman Spectrum of Epitaxial Graphene Grown on Ion Beam Illuminated 6H-SiC (0001)
ZHOU Zhi1, HU Ying1, SHAN Xin-Yan1, LU Xing-Hua1,2**
1Beijing National Laboratory for Condensed-Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190 2Collaborative Innovation Center of Quantum Matter, Beijing 100190
Abstract：Patterning SiC substrates with focused ion beam for growth of confined graphene nanostructures is interesting for fabrication of graphene devices. However, by imposing an ion beam, the morphology of illuminated SiC substrate surface is inevitably damaged, which imposes significant effects on the subsequent growth of graphene. By using confocal Raman spectroscopy, we investigate the effects of ion beam illumination on the quality of graphene layers that are grown on 6H-SiC (0001) substrates with two different growth methods. With the first method, the 6H-SiC (0001) substrate is flash annealed in ultra-high vacuum. Prominent defects in graphene grown on illuminated areas are revealed by the emergence of Raman D peak. Significant changes in D peak intensity are observed with Ga+ ion fluence as low as 105 μm?2. To eliminate the damage from the ion beam illumination, hydrogen etching is employed in the second growth method, with which prominent improvement in the quality of crystalline graphene is revealed by its Raman features. The defect density is significantly reduced as inferred from the disappearance of D peak. The Raman shift of G peak and 2D peak indicates strain-released graphene layers as grown in such a method. Such results provide essential information for patterning graphene nano-devices.
2014, Vol. 31 
