P. Zhao, E. Rusli, J. H. Xia, C. M. Tan, Y. Liu, C. C. Tin, S. F. Yoon, W. G. Zhu, and J. Ahn. “Study of carbon in thermal oxide formed on 4H-SiC by XPS,” Silicon Carbide and Related Materials 2004, Materials Science Forum, vol. 483-485, pp. 653-656, 2005.