Electronic structure of C and N co-doped TiO_2: A combined hard x-ray photoemission spectroscopy and density functional theory study

摘要

We have studied the electronic structure of C and N co-doped TiO_2 using hard x-ray photoelectron spectroscopy and first-principles density functional theory calculations. Our results reveal overlap of the 2p states of O, N, and C in the system which shifts the valence band maximum towards the Fermi level. Combined with optical data we show that co-doping is an effective route for band gap reduction in TiO_2. Comparison of the measured valence band with theoretical photoemission density of states reveals the possibility of C on Ti and N on O site.