Bandgap narrowing in high dopant tin oxide degenerate thin film produced by atmosphere pressure chemical vapor deposition

Antimony-doped tin oxide (SnO₂:Sb) thin films were prepared by atmospheric pressure chemical vapor deposition. Precursors were mixed with gaseous SnCl₄, SbCl₅, and oxygen. Both antimony and chlorine ions became involved in doping and reduced resistivity. The figure of merit suggested that films deposited at 500 °C with the ratio of SnCl ₄/SbCl₅ equals to 0.5 have the best quality. The dopant in the degenerate films narrowed the bandgap because of interaction between electrons and impurities. A mathematical model of the shifting in bandgap is proposed with the consideration of the effective mass of the carriers and well fitted to the experimental results.