Properties of Highly Transparent Conductive Ga-Doped ZnO Films prepared on Polymer Substrates by Reactive Plasma Deposition with DC Arc Discharge

Highly transparent conductive polycrystalline Ga-doped ZnO (GZO) films with a thickness of about 100nm prepared on cyclo-olefin polymer (COP) or glass substrates at various temperatures below 90 degrees C by ion plating with DC-arc discharge were investigated. A systematic study has been made of the influence of substrate temperature T(s) on the structural, electrical, optical and residual stress properties of GZO films. An increase in T(s) resulted in a beneficial effect on the crystallinity, electrical conductivity and transmission in the visible (VIS) range regardless of the type of substrate. The minimum resisitivity for GZO on glass and COP substrates was as low as 5.0 mu ohm m and 5.8 mu ohm m, respectively. For all the GZO films with average optical transmission above 90% in the VIS region, with increasing T(s), the optical absorption loss in the visible range decreased according in order of increasing Hall mobility. All the GZO films were found to be compressively stressed. The residual stresses, evaluated from the XRD spectrum, in GZO films on glass substrates are a decreasing function of T(s), whereas they are an increasing function of T(s) for GZO films on COP substrates. This finding indicates that for the GZO films on COP substrates deposited at higher temperature, thermal stress is dominant.