Linear, non-linear optical properties and magnetic studies of spray pyrolysis nanocrystalline Sn1-xCoxO2 films for multifunctional optoelectronic and spintronic applications

Abstract

Abstract In this paper, the structural, morphological, linear & non-linear optical, and magnetic properties of spray pyrolysis nanostructured Sn1-xCoxO2 thin films (0 ≤ x ≤ 0.08) were studied employing X-ray diffraction (XRD), atomic force microscope (AFM), spectrophotometric, and vibrating sample magnetometer (VSM) techniques, respectively. A tetragonal type structure was observed for films without any sign of impurities. XRD with Rietveld refinement analysis further revealed an increase in lattice parameters and unsystematic changes in crystallite size. AFM micrograph analysis shows that the surface roughness and root mean square roughness of the film are improved with increasing Co doping. Moreover, the spectrophotometry results indicate a direct optical transition for the film with an energy band gap reduces from 3.8 eV (x = 0) to 3.34 eV (x = 0.07) due to the rise in structural disorder and the increase in the density of localized states. The optical constants are calculated from the light transmission spectrum using the envelope method of Swanepoel. It is seen that the overall behavior of the refractive index n(λ) and extinction coefficient k(λ) increase with increasing of Co content. The dispersive oscillator parameters estimated from the single-oscillator Wemple–DiDomenico model were used to determine the non-linear optical parameters, such as the third-order non-linear optical susceptibility χ(3) and non-linear refractive index n2. Finally, intrinsic room temperature ferromagnetism is observed, which is interpreted based on the bound magnetic polarons model. In conclusion, Co doping in SnO2 host semiconductor nanocrystalline films enhances their optical and magnetic characteristics, making it a potential candidate for multifunctional applications like optoelectronics and spintronics devices.