Highly transparent conducting and enhanced near-band edge emission of SnO2:Ba thin films and its structural, linear and nonlinear optical properties

Abstract

In this paper, we reported the investigations of the structural, optical and photoluminescence properties of 3 at % Ba-doped SnO2 (SnO2:Ba) thin films under various annealing temperatures. X-ray diffraction analysis exhibits that the SnO2:Ba thin films have a polycrystalline tetragonal rutile structure of SnO2 phase and a nanometric dimension. The post-annealing treatment improves the crystallinity and decreases the crystal imperfections such as lattice strain and dislocation density. Field emission scanning electron microscopy analysis shows that the annealing treatment increases the crystallites agglomeration and minimizes the void fraction in the films. Based on the results, the maximum transmittance of 90%, the lowest resistivity of 6.95 × 10−4 Ω cm and the highest Haacke's figure of merit of 5.02 × 10−3 Ω−1 are obtained for the film annealed at 873 K. The UV–Vis spectra reveal that as the annealing temperature increases from 673K to 873 K, the transmittance threshold is blue-shifted which indicates the systematic increase in the optical band gap (3.19–3.85 eV) of the SnO2:Ba samples. Moreover, we have discussed the dispersion parameters, dielectric constants, nonlinear refractive index and third-order nonlinear susceptibility. A dominant visible emission band at ~ 486 nm is observed for the as-deposited sample, whereas the samples annealed at 773 and 873 K exhibit a high intense near band edge emission in the ultraviolet region.