The possibility of a defect-related mechanism in laser-deposited thin films was studied by using 4-point resistivity and photoluminescence techniques. It was found that there was a correlation between the photoluminescence spectrum and the wavelength dependence of the photo-induced conductivity. Peaks in the luminescence spectrum changed their intensity upon initiation of the photo-induced state. The results supported an O vacancy defect model, for photo-induced persistent conductivity and superconductivity, in which the O vacancies acted as weakly luminescent F-centers under illumination.

J.F.Federici, D.Chew, B.Welker, W.Savin, J.Gutierrez-Solana, T.Fink, W.Wilber: Physical Review B, 1995, 52[21], 15592-7