Scratch behavior, microstructure, resistivity and optical properties of indium tin oxide film grown at low deposition temperature

Indium tin oxide (ITO) films prepared by RF magnetron sputtering were characterized by Hall measurement, optical transmission spectra, X-ray diffraction (XRD), atomic force microscopy (AFM) and scratch testing. Deposition was performed at low temperature in different Ar sputtering pressures. The adhesion between the film and the substrate was estimated quantitatively by a scratch testing, in which a special attention was paid to the different stages. It can be found that the significant adhesion improvement is obtained in the ITO films deposited on the polymethyl methacrylate (PMMA) substrate with decreasing of the Ar sputtering pressure. The surface morphology and the resistivity of the ITO films are also significantly dependent on the Ar sputtering pressure. The low temperature films consist of an amorphous phase, the resistivity (1.25×10^-3 Ω·cm) and high transmittance (90%) in a visible range can be obtained in the Ar pressure 0.8 Pa. The typical resistivities are mainly governed by the carrier concentration in the ITO films at biggish Ar sputtering pressure, and the optical band gap is about 3.85 eV for all the ITO films.