Local chemical states and thermal stabilities of nitrogen dopants in ZnO film studied by temperature-dependent x-ray photoelectron spectroscopy

Local chemical states and thermal stabilities of N dopants in ZnO:N film are investigated by temperature-dependent x-ray photoelectron spectroscopy. Different types of N local states are detected, including N2 molecules occupying O sites [(N2)O], –NO species, substitutional N atoms in O- and N-rich local environments (α- and β-NO). Compared to the β-NO, the α-NO shows a better thermal stability up to 723 K. However, the transformation from α-NO acceptor to undesirable (N2)O donor occurs above 743 K. The variation of N local states also affects Zn and O binding energies. Photoluminescence studies indicate the shallow acceptor nature of α-NO.