Local electronic structure of phosphorus-doped ZnO films investigated by X-ray absorption near-edge spectroscopy

Using X-ray absorption near-edge structure spectroscopy (XANES), we investigate the local electronic structure of phosphorus (P) and its chemical valence in laser-ablated n-type (as-grown), and p-type (annealed) P-doped ZnO thin films. Both the P L 1- and P L 2,3-edge XANES spectra reveal that the valence state of P is 3− (P3−) in the p-type as well as in the n-type P-doped ZnO. However, the peak intensity is stronger in the former than that in the latter, suggesting that P replaces O (O2− sites with the P3−) after rapid thermal annealing. The Zn and O K-edges XANES spectra consistently demonstrate that, in the p-type state, P ions substitutionally occupy O sites in the ZnO lattice.