Electronic properties of nickel-doped TiO₂ anatase

Atomistic details of electron transfer in semiconductor materials are characterized for TiO₂ thin film surfaces doped with nickel. A periodic slab model of eight atomic layers exposes the (1 0 0) crystallographic surface and is covered with a monolayer of water. The density of states, absorption spectra, partial charge densities, molecular dynamics, and non-adiabatic couplings are compared between doped and undoped models. Our results show that Ni doping improves several electronic properties including lowering the band gap, increasing visible light absorption, and shortening the relaxation time of holes rather than electrons, which maximizes charge separation. The different mechanisms of electron and hole dynamics are discussed. The computed characteristics of a doped semiconductor material have practical potential for increasing efficiency of a photo-electrochemical cells. (paper)