Selective faceting induced by Hexagonal Boron Nitride on curved Platinum substrate
This work combines experimental investigations and first-principles calculations to study hexagonal boron nitride (hBN) growth on a curved Pt(331) substrate. Low-energy electron diffraction (LEED) and scanning tunnelling microscopy (STM) were employed to investigate the structural properties, observing that hBN growth led to faceting with several stable facets: Pt(111), Pt(221), Pt(441), Pt(881), and Pt(110). Additionally, the electronic properties were examined by X-ray photoemission spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS), revealing an increase in the hBN-substrate interaction strength, from the weakest at the Pt(111) to the strongest at the Pt(110). Density functional theory (DFT) calculations confirm that the selective faceting mechanism is induced by hBN, which changes the order of relative stability of the uncovered facets. Although a complete understanding of the process is not achievable using only thermodynamical arguments, the comparison between hBN adhesion energies and clean surface free energies clearly indicates that some facets are stabilized with respect to others by stronger overlayer-substrate interaction, whereas for others the clean surface energetics plays the dominant role.