Properties of indium tin oxide films deposited by RF magnetron sputtering at various substrate temperatures

Polycrystalline indium tin oxide (ITO) is one of the important materials as transparent conducting oxide layer in thin film solar cells, digital displays and other similar applications. In this study, ITO films were deposited onto float glass substrates by RF magnetron sputtering method at different substrate temperatures (50-175°C) with discharge power of 60 W and work pressure of 0.25 Pa. The ITO films were characterised by X-ray diffraction, scanning electron microscope analysis, optical and electrical measurement. The structural, optical and electrical properties of the ITO films show a strong dependence on the substrate temperatures. The structural and electrical measurement results indicate that the donor impurities are due to the substitution of Sn into In sites, which causes an expansion of the lattice. As the temperature is increased from 50 to 175°C, the preferred crystal orientation changes from [222] to [100], the transmittance in the visible wave band is beyond 80%, and the electrical resistivity decreases to 7.32 × 10^-4 Ω.cm at 175°C substrate temperature. However, the optical bandgap is slightly increasing with the increasing of the substrate temperature.