Nonlinear optical effects in In2O3:Sn-glass nano-interfaces

Nano-sized thin layers (1-2 nm) between In2O3:Sn (ITO) crystalline films and glass substrates were studied using photo-induced optical and second-order nonlinear optical (second harmonic generation) effects. Photo-induced changes in the effective energy gap were found for the first time in In2O3 films doped using different amounts of Sn deposited on the glass substrates. The photo-induced second-order nonlinear optical susceptibilities show a good correlation with the behaviour of the fundamental absorption edge. The maximal response of the photo-induced signal was observed for pump-probe delay times equal to approximately 26 ps. The experimental measurements performed indicate that the observed effects are stimulated by two factors: the first one is connected with the interface potential gradients on the boarder glass-ITO film. The second one is a consequence of the additional polarization due to the insertion of differing amounts of Sn atoms. The observed phenomenon may be proposed as a sensitive tool for the investigation of thin semiconducting-glass interface layers.