Energy Level Evolution and Oxygen Exposure of Fullerene/Black Phosphorus Interface

The heteroepitaxial growth of fullerene (C60) on single-crystal black phosphorus (BP) has been studied using low-energy electron diffraction, X-ray and ultraviolet photoelectron spectroscopy, and density functional theory simulation. The occupied orbital features from C60 observed in the photoelectron spectra for C60/BP interface are slightly broadened at higher coverages of C60 and exhibit no direct evidence of hybridization, demonstrating that the C60/BP interaction is physisorption. Oxygen exposure of interface leads to obvious oxidation of BP in which C60 bridges the large electron-transfer barrier from BP to oxygen and plays an important role for the production of O2– and oxidation of BP. Our findings suggest that C60 does not form an ideal protection layer as the other n-type semiconductors. With the assistance of density functional theory calculations, the oxidized phosphorus at the interface prevents further charge transfer from BP to C60.