Si diffusion path for pit-free graphene growth on SiC(0001)

G. F. Sun, Y. Liu, S. H. Rhim, J. F. Jia, Q. K. Xue, M. Weinert, and L. Li
Phys. Rev. B 84, 195455 – Published 23 November 2011

Abstract

Density functional theory calculations reveal that the interfacial 63 × 63 structure [a warped graphene layer with periodic inclusions of pentagon-hexagon-heptagon (H5,6,7) defects] facilitates a Si diffusion path vertically through the interface layer during epitaxial growth of graphene on SiC(0001). The calculated diffusion barrier is 4.7 eV, competitive with Si interstitial diffusion of ∼3.5 eV in SiC [M. Bockstedte et al., Phys. Rev. B 68, 205201 (2003)]. Scanning tunneling microscopy study shows that, for growth in an Ar background, where Si desorption is suppressed and all diffusion channels contribute, graphene films with reduced pit density can be grown on nominally flat SiC substrates. On the other hand, for Si diffusion-limited growth in ultrahigh vacuum, the Si interstitial diffusion is the energetically favorable path where the step edges serve as the necessary outlet toward Si desorption. The much higher density of step edges on vicinal substrates also facilitates the growth of pit-free graphene.

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  • Received 16 June 2011

DOI:https://doi.org/10.1103/PhysRevB.84.195455

©2011 American Physical Society

Authors & Affiliations

G. F. Sun1,2, Y. Liu1, S. H. Rhim1, J. F. Jia3,4, Q. K. Xue2,3, M. Weinert1, and L. Li1,*

  • 1Department of Physics and Laboratory for Surface Studies, University of Wisconsin, Milwaukee, Wisconsin 53211, USA
  • 2Institute of Physics, Chinese Academy of Sciences, Beijing 100190, P. R. China
  • 3Department of Physics, Tsinghua University, Beijing 100084, P. R. China
  • 4Department of Physics, Shanghai Jiaotong University, Shanghai 200240, P. R. China

  • *lianli@uwm.edu

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Issue

Vol. 84, Iss. 19 — 15 November 2011

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