Microstructure and properties of indium tin oxide thin films deposited by RF-magnetron sputtering

Tin-doped indium oxide (ITO) thin films were prepared using conventional radio frequency (RF) planar magnetron sputtering equipped with IR irradiation using a ceramic target of In2O3/SnO2 with a mass ratio of 1:1 at various IR irradiation temperatures TI (from room temperature to 400°C). The refractive index, deposited ratio, and resistivity are functions of the sputtering Ar gas pressure. The microstructure of ITO thin films is related to IR TI, the crystalline seeds appear at TI = 300°C, and the films are amorphous at the temperature ranging from 27°C to 400°C. AFM investigation shows that the roughness value of peak-valley of ITO thin film (Rp-v) and the surface microstructure of ITO thin films have a close relation with TI. The IR irradiation results in a widening value of band-gap energy due to Burstein-Moss effect and the maximum visible transmittance shifts toward a shorter wavelength along with a decrease in the film's refractive index. The plasma wavelength and the refractive index of ITO thin films are relative to the TI. XPS investigation shows that the photoelectrolytic properties can be deteriorated by the sub-oxides. The deterioration can be decreased by increasing the oxygen flow rate (fo2), and the mole ratio of Sn/In in the samples reduces with an increase in fo2.