Structural, optical and electrical properties studies of ultrasonically deposited tin oxide (SnO2) thin films with different substrate temperatures

Abstract Undoped thin films of tin oxide (SnO 2 ) were deposited onto microscopic glass substrates using an ultrasonic spray pyrolysis technique. The thin films were deposited on glass at large scale of temperature ranged in 400–500 °C and stepped by 20 °C. The effect of substrate temperature on structural, electrical and optical properties was studied using X-ray diffraction (XRD), UV–visible spectrophotometer and a conventional four point probe technique. XRD showed that all the films were polycrystalline with major reflex along (1 1 0) plane, manifested with amelioration of grain size from 6.51 to 29.80 nm upon increasing substrate temperature. Lattice constant ‘ a ’, ‘ c ’, microstrains and dislocation densities were affected by the substrate temperature. Transmittance of about 75% at more than 800 nm for films prepared at 480 °C has been observed. With increasing the substrate temperature the direct band gap energy was averaged in 4.03–4.133 eV. Plasma frequency ( ω p ) was estimated to be 4 ⋅ 10 14  Hz and optically estimated free electrons number N leading to predict that, in SnO 2 material, the effective density of conduction band states is about 5 ⋅ 10 19  cm −3 . Among all the samples the film that deposited at 480 °C exhibited lowest resistivity of about 9.19 × 10 −3  Ω cm.