Effect of Hydrogen on the Properties of RF-Magnetron Sputtering ZnO:Al Films as an Alternative to Commercially Available TCO Films

Abstract

Transparent conducting ZnO:Al thin films with lowest electrical resistivity and sheet resistance 3.89 × 10−4 Ω cm and 7.65 Ω/□ were developed by RF-magnetron sputtering using Ar + H2 as sputtering gas at 250 °C. ZnO:Al films are highly polycrystalline hexagonal wurtzite, (002) oriented and grain size are around 30 nm. The highest carrier concentration and mobility of our lab deposited ZnO:Al films are (~1021 cm−3) and 8.93 cm2/V s respectively. RF-sputtered ZnO:Al films are self textured and surface roughness of ZnO:Al films varies with H2 dilution ratio and ultimately affects on Haze factor. Haze factor varies from 36 to 42.8 for introducing different gas ambient during deposition. Blue and green photoluminescence emission peaks are observed at 432 nm (2.87 eV) and 541.5 nm (2.29 eV) respectively in H2 gas deposited ZnO:Al films. Both ZnO:Al and commercial TCO films have almost similar electrical properties except mobility and visible optical transmittance maxima, but still show 30 % higher optical transmittance at longer wavelength region of solar spectrum and U-type surface morphology. Systematic analysis of different materials properties, elemental analysis and surface texture of non-stoichiometric ZnO:Al films are studied and latest status on electrical, optical as well as morphological studies of magnetron sputtered ZnO:Al films are reported. Finally, the possible solutions for expected outcomes are discussed.