Effects of two kinds of intercalated In films on quasi-free-standing monolayer graphene formed above SiC(0001)

The effects of In atoms intercalated between the n-type 6H-SiC(0001) substrate and the (6 root 3 x 6 root 3)R30 degrees zero layer (ZL) on the interface morphology, chemical composition and electron band structure were investigated by scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), core-level/valence-band photoemission spectroscopy (PES) and angle-resolved photoemission spectroscopy (ARPES). As a result of In intercalation, two kinds of ordered In films depending on the thickness of In as well as the annealing temperature were formed under quasi-free-standing monolayer graphene (QFMLG) transformed from ZL. One is a bilayer film, which is stable under 800 degrees C. The other is a monolayer film composed of In adatoms of a (root 3 x root 3)R30 degrees structure, which survives over 800 degrees C. The latter induces electron doping of the QFMLG stronger than the former. In addition, the QFMLG on the (root 3 x root 3)R30 degrees film becomes more n-doped under higher annealing temperature, which is due to a vacancy increment of the In film. (C) 2019 Elsevier Ltd. All rights reserved.