Electronic work function modulation of phosphorene by thermal oxidation

Abstract

In this study, we evaluate the variation of the work function of phosphorene during thermal oxidation at different temperatures. The ultraviolet photoelectron spectroscopy results show an N-shaped behaviour that is explained by the oxidation process and the dangling-to-interstitial conversion at elevated temperatures. The exfoliation degree and x-ray photoelectron spectroscopy confirm the formation of native oxides in the top-most layer that passivates the material. Ex-situ XPS reveals the full oxidation of monolayers at temperatures higher than 140 C, but few-layer phosphorene withstands the thermal oxidation even up to 200 C with slight modifications of the A 2g/A 1g and A 2g/B 2g vibrational mode ratios and a weak fluorescence in the Raman spectra of the heat-treated samples.