Two-dimensional emission patterns of secondary electrons from graphene layers formed on SiC(0 0 0 1)

We used spectroscopic photoemission and low-energy electron microscopy to measure two-dimensional (2D) emission patterns of secondary electrons (SEs) emitted from graphene layers formed on SiC(0 0 0 1). The 2D SE patterns measured at the SE energies of 0-50 eV show energy-dependent intensity distributions in the 6-fold symmetry. The SE patterns exhibit features ascribed to energy band structures of 2D free electrons, which would prove that electrons are partially confined in thin graphene layers even above the vacuum level.