Amorphous HfO2 films prepared by e-beam deposition exhibited room-temperature photoluminescence  in the visible range, i.e., at ~620 and 700nm, due to O vacancies involved during deposition. This photoluminescence could be enhanced by two orders in intensity by crystallizing the amorphous films in flowing argon, where a large amount of O vacancies were introduced, and could be diminished by removal of the O vacancies by annealing HfO2 films in O. This was expected to help to understand the defect-property relationship and provide ways of tuning the photoluminescence properties of HfO2 films.

Oxygen Defect Induced Photoluminescence of HfO2 Thin Films. J.Ni, Q.Zhou, Z.Li, Z.Zhang: Applied Physics Letters, 2008, 93[1], 011905