2D graphitic-like gallium nitride and other structural selectivity in confinement at the graphene/SiC interface

Beyond the predictions routinely achievable by first-principles calculations and using metal-organic chemical vapor deposition (MOCVD), we report a GaN monolayer in a buckled geometry obtained in confinement at the graphene/SiC interface. Conductive atomic force microscopy (C-AFM) was used to investigate vertical current injection across the graphene/SiC interface and to establish the uniformity of the intercalated regions. Scanning transmission electron microscopy (S/TEM) was used for atomic resolution imaging and spectroscopy along the growth direction. The experimentally obtained value of the buckling parameter, 1.01 +/- 0.11 angstrom, adds to the existing knowledge of buckled GaN monolayers, which is based solely on predictive first-principles calculations. Our study reveals a discontinuity in the anticipated stacking sequence attributed to a few-layer graphitic-like GaN structure. Instead, we identify an atomic order suggestive of ultrathin gallium oxide Ga2O3, whose formation is apparently mediated by dissociative adsorption of oxygen onto the GaN monolayer.