Enhanced optoelectronic and catalytic properties of Sm doped SnO2 thin films

Herein, we report the optoelectronic and malachite green (MG) aqueous dye model pollutant degradation characteristics of samarium (Sm) doped tin oxide (SnO2:Sm) thin films deposited on glass substrate by chemical spray pyrolysis technique. The tetragonal crystal structure and polycrystalline nature were elucidated from X-ray diffraction (XRD) analysis, and the calculated crystallite size using Scherrer's relation was found to vary between 36 and 45 nm. A high optical transparency of 92 % was achieved for SnO2:Sm (3 wt%). The extrapolation of linear fit indicates a slight decrement in the band gap. Energy dispersive X-ray analysis (EDAX) confirmed the presence of Sn, O and Sm elements and their composition. The quantitative compositional percentage of Sn, O and Sm was determined by X-ray photoelectron spectroscopy (XPS) analysis. The scanning electron micrographs (SEM) showed polyhedron-like shaped grains with cracks and void-free film surface. The 3 wt% Sm:SnO2 thin film exhibited a higher average surface roughness (19.63 nm) than other films. Strong ultraviolet (365 nm), blue (493 nm), and green (520 nm) emissions were observed for all the films, as recorded by photoluminescence (PL) studies. High electron concentration (7.9 x 1020/cm3), low resistivity (0.356 x 10-3 Omega cm), and a high figure of merit (FOM, 5.11 x 10-2 Omega- 1) were obtained for 3 wt % of SnO2:Sm thin films. Furthermore, a relatively high photocurrent (8.22 mA) was attained for the 3 wt% Sm:SnO2 thin film. Enhanced photocatalytic efficiency (95 %) was achieved for the 4 wt% Sm:SnO2 film against MG dye aqueous solution. The results obtained in the present study demonstrate high optical transparency, electrical conductivity, enhanced FOM, and photocatalytic degradation efficiency for 3 and 4 wt% Sm-doping, respectively. Therefore, Sm-doped SnO2 could be useful for developing and designing novel devices for optoelectronic and photocatalytic applications.