Effect of trivalent rare-element doping on structural and optical properties of SnO₂ thin films deposited by dip coating deposition technique

Erbium doped tin oxide thin films (SnO₂:Er) were prepared by the sol–gel method using dip coating technique. X-ray diffraction patterns showed a decrease of crystallinity in the films with increase in erbium doping concentration (0–5 mol%). Scanning electron microscopy analysis revealed an inhibition of grain growth with increase in erbium doping concentration. The film surfaces were uniform with crack free appearance. X-ray photoelectron spectroscopy revealed the presence of erbium, oxygen, tin oxide in the SnO₂:Er films. The resistivity of the SnO₂:Er films decreased and then increased with the increase in erbium doping concentration. The optical properties of the films have been studied from transmission spectra. An average transmittance of 80 % in ultraviolet–visible region was observed for all the films. Optical band gap energy (E_gap) of SnO₂:Er films were observed to increase with the increase in doping concentration. Photoluminescence spectra of the films exhibited an increase in the emission intensity for (0–3 mol%) and decreased for 5 mol% erbium doping film. Such SnO₂:Er films with wide band gap and luminescence efficiency are applicable in blue and ultraviolet optical devices, such as light-emitting diodes and laser diodes.