Experimental determination of conduction and valence bands of semiconductor nanoparticles using Kelvin probe force microscopy

The ability to predict a semiconductor's band edge positions in solution is important for the design of photocatalyst materials. In this paper, we introduce an experimental method based on Kelvin probe force microscopy (KPFM) to estimate the conduction and valence band edge energies of semiconductors, which has never been demonstrated experimentally. We test the method on six well known semiconductor materials: α-Fe ₂O ₃, CeO ₂, Al ₂O ₃, CuO, TiO ₂, and ZnO. The predicted band edge positions for α-Fe ₂O ₃, Al ₂O ₃, and CuO were not statistically different from the literature values. Except CeO ₂, all other metal oxides had consistent upward bias in the experimental determination of band edge positions probably because of the potential shielding effect of the adsorbed surface water layer. This experimental approach represents a unique way of probing the band edge energy positions of metal oxide materials without using the thermodynamic information (e.g., enthalpy or entropy), which is often not available for new synthetic or complex materials.