Electrical and band-gap properties of amorphous zinc–indium–tin oxide thin films

Zinc–indium–tin oxide (ZITO) films were grown by pulsed-laser deposition. Three different material compositions were investigated: ZITO-30, ZITO-50 and ZITO-70 in which 30%, 50% and 70%, respectively, of the indium in the In2O3 structure was replaced by substitution with zinc and tin in equal molar proportions (co-substitution): In2−2xZnxSnxO3, where x=0.3, 0.5, 0.7. All ZITO films grown at room temperature were amorphous. The first evidence of crystallinity was observed at higher deposition-temperature as the degree of co-substitution was increased. A decrease in mobility and conductivity was also observed as the degree of co-substitution was increased. The highest mobility for ZITO-30 and ZITO-50 was observed at deposition temperatures just prior to crystallization. The effect of deposition temperature on carrier concentration was minor compared to the effect of oxygen partial pressure during deposition.