Optical Property and the Relationship between Resistivity and Surface Roughness of Indium Tin Oxide Thin Films

Indium tin oxide (ITO) films with high visible transmittance were fabricated on polymethyl methacrylate (PMMA) flexible substrate at room temperature by radio frequency (RF) magnetron sputtering. The deposition rate, microstructure, surface roughness, electrical and optical properties of these films have been investigated as a function of Ar partial pressure from 0.2- 1.4 Pa. The microstructure and surface morphology of ITO films were studied using X-ray diffraction (XRD) and atomic force microscopy (AFM), the resistivity was investigated by four-point probe technology, and the optical transmittance was determined by UV-Vis spectrophotometer. The results show that the resistivity of the ITO film decreases with increasing Ar partial pressure from 0.2 Pa to 0.8 Pa, and then increases with increasing Ar partial pressure from 0.8 Pa to 1.4 Pa. The resistivity varied from 1.25×10-3 Ω.cm to 2.33 ×10-3 Ω.cm and the average transmission in the visible range was 90%. It was also found that the microstructure is amorphous and the surface roughness decreases from 1.438 nm to 0.813 nm with increasing Ar partial pressure to 1.1 Pa. The most interesting fact is that the resistivity increases with the increasing surface roughness, which indicates that the surface roughness also plays an important role in electrical properties of the ITO films.