Study of light-emitting defects induced by 100 MeV Ag ion irradiation in potassium sodium niobate thin films

Here, we report the effects of swift heavy ion (SHI) irradiation on the photoluminescence (PL) properties of (K, Na)NbO3 (KNN) films deposited using RF magnetron sputtering in mixed atmosphere of argon and oxygen gas. In order to comprehend the role of defects created by SHI irradiation on PL properties, films were irradiated using 100 MeV Ag ions by varying ion fluence. X-ray photoelectron spectroscopy (XPS) results show the enhancement in oxygen vacancies upon irradiation with ion fluence which is confirmed from the reduction in contribution of Nb5+ state as well as lattice oxygen. The enhanced hump towards lower binding energy of Nb 3d XPS spectra indicates the increase in sub-oxides after irradiation. PL results revealed the band-to-band or near-band-edge transition in near ultraviolet region along with blue emission associated with defects present in KNN. PL results show that the deep-traps between the valence band maximum and conduction band minimum are increased with ion fluence, and the transitions from defect states are enhanced due to increase in the density of defects at higher fluence. The decay lifetime is found to improve with ion fluence up to 5 x 10(12) ions/cm(2) and is decreased at higher fluence. In this report, SHI irradiation induced variation in the defect emission with decay lifetime of KNN films is explained.