Structural, optical and non-linear optics properties of highly doped molybdenum indium oxide thin film

Molybdenum (Mo)-doped In₂O₃ thin film with 10 wt% was successfully prepared by evaporation method. After annealing at 600 °C the film changes it colour from very dark to a clear transparent film. SEM and AFM analysis reveal that the film is continuous with high metallic coverage >98 % and exhibits a granular structure with typical grain size of 50 nm. More interestingly, the film shows more than 90 % transparency from visible to near infrared region and with wide optical band gap of 4.26 eV. The widening of the band gap is due to the Burstein–Möss (BM) effect as Mo will occupy In sites within the structure of the film thus increasing the carrier concentration thus enhancing its electrical properties. The nonlinear optical properties of Mo-doped In₂O₃ film with glass substrate were investigated using z-scan technique. Under cw excitation the film exhibits large reverse saturation absorption and negative nonlinearities. The real and imaginary parts of third order susceptibility of the film were measured and found that the imaginary part which arises from the change in absorption is dominant.