Temperature Dependence of Epitaxial Graphene Formation on SiC(0001)
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The formation of epitaxial graphene on SiC(0001) surfaces is studied using atomic force microscopy, Auger electron spectroscopy, electron diffraction, Raman spectroscopy, and electrical measurements. Starting from hydrogen-annealed surfaces, graphene formation by vacuum annealing is observed to begin at about 1150°C, with the overall step-terrace arrangement of the surface being preserved but with significant roughness (pit formation) on the terraces. At higher temperatures near 1250°C, the step morphology changes, with the terraces becoming more compact. At 1350°C and above, the surface morphology changes into relatively large flat terraces separated by step bunches. Features believed to arise from grain boundaries in the graphene are resolved on the terraces, as are fainter features attributed to atoms at the buried graphene/SiC interface.
KeywordsGraphene silicon carbide semiconductor field-effect transistor
The authors are grateful to W.J. Choyke, R.P. Devaty, W. Hu, K. Oman, N. Srivastava, and Y. Yin for useful discussions and for technical assistance. This work was supported by the National Science Foundation (Grant DMR-0503 748), and by the Defense Advanced Research Projects Agency through a contract administered by the Air Force Research Laboratory (Contract FA8650-08-C-7823). The work is approved by DARPA for public release, distribution unlimited. Use of the Center for Nanoscale Materials at Argonne National Laboratory was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. Opinions are those of the authors and are not necessarily endorsed by the funding sources.