The effect of Ar:O2 gas ratios on the structural and optical properties of RF sputter-deposited La2O3-doped ZnO thin films

Abstract

Due to their unique scintillation, phosphorescence, magnetic, and catalytic properties, rare earth oxide compounds have recently become one of the most in-demand materials used in different ways. The current study investigated the impact of Ar:O2 gas flow variation on the deposition of La2O3-doped zinc oxide thin films (TFs) on silicon dioxide (SiO2) substrates using the radio frequency sputtering technique. FE-SEM analysis has shown a smooth surface topology and purity of La2O3-doped ZnO TFs. X-ray diffraction analysis exhibited a single-phase hexagonal wurtzite-type structure in TFs. A UV–Vis–IR spectrophotometer examined the optical characteristics of ZnO and La2O3-doped ZnO TFs in 300–800 nm wavelength range. The bandgap of La2O3 doped ZnO TFs changed from 2.9 to 3.1 eV as argon and oxygen concentrations in (Ar:O2) gas flow changed. A variation in optical constants such as dielectric constants, refractive index, and extinction coefficient was observed when ZnO and La2O3-doped ZnO TFs were exposed to variable (Ar:O2) gas flow ratios. The photoluminescence analysis of ZnO and La2O3-doped ZnO TFs was performed at an excitation wavelength of 330 nm. Atomic force microscopy further revealed that La2O3 doping resulted in smoother surfaces and smaller grain sizes. This comprehensive study provides valuable insights into the relationship between doping, gas composition, and the optical and structural properties of ZnO TFs. The obtained results on the optimal flow rate of argon gas provide valuable insights for determining the appropriate deposition conditions of La2O3-doped ZnO TFs, specifically for their application in solar thermal systems.