Van der waals epitaxial growth of graphene on sapphire by chemical vapor deposition without a metal catalyst

Jeonghyun Hwang, Moonkyung Kim, Dorr Campbell, Hussain A. Alsalman, Joon Young Kwak, Shriram Shivaraman, Arthur R. Woll, Arunima K. Singh, Richard G. Hennig, Sandeep Gorantla, Mark H. Rümmeli, Michael G. Spencer