Influence of Substrate Bias Voltage on the Electrical and Optical Properties of IWO Thin Films

Transparent conductive tungsten (W) doped indium oxide (In2O3; IWO) films were deposited at different substrate bias voltage (-V-b) conditions at room temperature on glass substrates by radio frequency (RF) magnetron sputtering and the influence of the substrate bias voltage on the optical and electrical properties was investigated. As the substrate bias voltage increased to -350 V-b, the IWO films showed a lower resistivity of 2.06 x 10(-4) Omega cm. The lowest resistivity observed for the film deposited at -350 V-b could be attributed to its higher mobility, of 31.8 cm(2)/Vs compared with that (6.2 cm(2)/Vs) of the films deposited without a substrate bias voltage (0 V-b). The highest visible transmittance of 84.1 % was also observed for the films deposited at the -350 V-b condition. The X-ray diffraction observation indicated the IWO films deposited without substrate bias voltage were amorphous phase without any diffraction peaks, while the films deposited with bias voltage were polycrystalline with a low In2O3 (222) diffraction peak and relatively high intensity (431) and (046) diffraction peaks. From the observed visible transmittance and electrical properties, it is concluded that the opto-electrical performance of the polycrystalline IWO film deposited by RF magnetron sputtering can be enhanced with effective substrate bias voltage conditions.