Phosphorus doping of insulating metal-oxide surfaces

Achieving control over the electronic properties of the oxide surfaces is of pivotal importance to extend the applicability of the materials and also to improve on current applications. Serious limitations affect the extent of this control mainly since processes typically employed in industry to engineer oxide-containing materials result in complex morphologies and a priori unpredictable behavior of the generated materials. Based on pseudopotential DFT and in-situ characterization techniques, we tackled this problem for the specific goal of generating electron-rich surfaces through Group 5A doping (P atoms). We sought theory–experiment correlation on several levels: electronic density of states, electronic properties (NMR and surface workfunction (WF)), predicted surface morphology, and doping level. We focus on an atomic-level understanding of the morphology and the structure-properties relationships of realistic (hydroxylated) surfaces of P doped gamma Al₂O₃. We find that P doping leads to an enhanced surface electron density and a weakening of the WF of the oxide. The results provide a clear picture of the effect of P doping at the surface of gamma Al₂O₃, also predicting that the highest concentration of P atoms should occur at surface sites rich in undercoordinated O atoms.