Improved optoelectronic properties of Gd doped cadmium oxide thin films through optimized film thickness for alternative TCO applications

Abstract

Transparent and conducting thin films of pure and gadolinium(Gd) doped cadmium oxide (CdO) were deposited on glass substrates by RF magnetron sputtering at ambient temperature to develop indium free, alternate transparent conducting electrode for optoelectronic devices. The impacts of Gd doping and film thickness on physical properties of the deposited films were investigated. Mechanism of transmittance, conduction and the scattering process were also discussed. The films showed cubic structure with predominant orientation along (111) plane. All the deposited films were smooth and homogeneous with decreasing roughness from 2.23 nm to 1.69 nm for Gd doped CdO thin film. Pristine CdO film showed peculiar morphology of nano pyramidal shaped grains on the surface. The average transmittance of the films increased from 79% to 88% with the doping of Gd. The Gd doped CdO (GCO) film at a thickness of 900 nm exhibits a maximum transmittance of 93% in visible range. The Gd doped CdO film deposited at a thickness of 900 nm showed the best optoelectronic properties with high average transmittance (88%) and low resistivity (7.203 × 10−5 Ω cm). This result indicates that the Gd doped CdO thin films deposited with suitable thickness can be used as an alternative for high performance TCO in various optoelectronic devices.