Luminescence of Cr-doped ZnGa2O4 thin films deposited by pulsed laser ablation

Chromium-doped zinc gallate powder is synthesized via a solid-state reaction and subsequently deposited as a thin film on quartz substrates by using a pulsed laser deposition technique under two different deposition conditions. The films are characterized with X-ray diffraction, scanning electron microscopy, UV-vis spectrophotometry and luminescent measurements. As the oxygen pressure is changed from 0 to 1 Pa, we find that the grain size gets smaller, the crystallinity improves, the band-gap energy increases, the excitation peaks of the charge transfer band exhibit a remarkable blue-shift from 263 to 247 nm and the intensity of the red emission (694 nm) is enhanced. The results suggest that the structural and luminescent properties of ZnGa₂O₄:Cr^3 + thin film phosphors are improved by deposition at an oxygen pressure of 1 Pa.