Substrate temperature effect on structural, optical and electrical properties of vacuum evaporated SnO 2 thin films

Abstract

Tin oxide (SnO 2) thin films were deposited on glass substrates by thermal evaporation at different substrate temperatures. Increasing substrate temperature (T s) from 250 to 450 °C reduced resistivity of SnO 2 thin films from 18×10 -4 to 4×10 -4 Ω cm. Further increase of temperature up to 550 °C had no effect on the resistivity. For films prepared at 450 °C, high transparency (91.5%) over the visible wavelength region of spectrum was obtained. Refractive index and porosity of the layers were also calculated. A direct band gap at different substrate temperatures is in the range of 3.55-3.77 eV. X-ray diffraction (XRD) results suggested that all films were amorphous in structure at lower substrate temperatures, while crystalline SnO 2 films were obtained at higher temperatures. Scanning electron microscopy images showed that the grain size and crystallinity of films depend on the substrate temperature. SnO 2 films prepared at 550 °C have a very smooth surface with an RMS roughness of 0.38 nm. © 2012 Elsevier Ltd. All rights reserved.