Effect of erbium on the structural, morphological, and optical properties of SnO2 thin films deposited by spray pyrolysis

In the present work numerous compositions of Er-doped SnO2 thin films were made at 425 degrees C on a quartz glass substrate using spray pyrolysis method. The powder X-ray diffraction and X-ray photoelectron spectroscopy analysis confirms the tetragonal phase and surface chemical composition of as made Sn1-xErxO2 (x = 0.0, 0.01, 0.02, 0.03, 0.04, and 0.05) thin films. The grain size and RMS roughness of the films were estimated from the AFM measurements and the film surface has a saw-tooth-like morphology. The transmission spectra of the films are fallen in the visible range having between 60% and 80% transmittance with different Er concentration. The optical direct, indirect band gap and phonon energy values have been estimated. The photo-luminescence measurements under excitation at 325 nm show three distinct emission peaks, a broad hump positioned at 390 nm, two sharp peaks at 420 nm related to fin interstitials, and a sharp peak at 700 nm related to oxygen vacancies. The ER3+ in SnO2 increased the oxygen vacancies to maintain charge balance and as a result the intensity of emission peaks increases with Er content.