Chromaticity(b^*), Sheet Resistance and Transmittance of SiO_2-ITO Thin Films Deposited on PET Film by Using Roll-to-Roll Sputter System

Abstract

【This paper has relatively high technical standard and experimental skill. The fabrication of TCO film with high transparency, low resistance and low chromaticity require exact control of several competing factors. This paper has resolved these problems reasonably well, thus recommended for publication. Indium tin oxide(ITO) thin films were by D.C. magnetron roll-to-roll sputter system utilizing ITO and $SiO_2$ targets of ITO and $SiO_2$ . In this experiment, the effect of D.C. power, winding speed, and oxygen flow rate on electrical and optical properties of ITO thin films were investigated from the view point of sheet resistance, transmittance, and chromaticity( $b^*$ ). The deposition of $SiO_2$ was performed with RF power of 400W, Ar gas of 50 sccm and the deposition of ITO, DC power of 600W, Ar gas of 50 sccm, $O^2$ gas of 0.2 sccm, and winding speed of 0.56m/min. High quality ITO thin films without $SiO_2$ layer had chromaticity of 2.87, sheet resistivity of 400 ohm/square, and transmittance of 88% and $SiO_2$ -doped ITO Thin film with chromaticity of 2.01, sheet resistivity of 709 ohm/square, and transmittance of more than 90% were obtained. As a result, $SiO_2$ was coated on PET before deposition of ITO, their chromaticity( $b^*$ ) and transmittance were better than previous results of ITO films. These results show that coating of $SiO_2$ induced arising chromaticity( $b^*$ ) and transmittance. If the thickness of $SiO_2$ is controlled, sheet resistance value of ITO film will be expected to be better for touch screen. A four point probe and spectrophotometer are used to investigate the properties of ITO thin films.】