Influence of tin doping on the structural and physical properties of indium-zinc oxides thin films deposited by pulsed laser deposition

A detailed investigation of the structural and opto-electrical properties of tin-doped indium-zinc oxide thin films prepared by pulsed laser deposition was carried out. The substitution of indium for tin in Zn_kIn₂O_k+3 compounds (k=2, 3 and 5) (which structure is a mixture of homologous phases with different k, but mostly composed of the polytype having the target composition) led to a conductivity enhancement, caused by an increase in carrier concentration at low doping levels, whereas for higher doping levels a decrease in conductivity and carrier concentration together with an amorphisation of the films was noted. The best electrical properties (σ=2500 S/cm) were obtained for the Zn₂In_1.9Sn_0.1O_5+δ doped films having a layered Zn_kIn₂O_k+3-type structure with essentially k=2. Independently of the composition an 85-90% average transmittance in the visible region was obtained. In contrast the band gap of the Sn-doped film slightly increased with tin ratio, in agreement with the Burstein-Moss theory.