The transition metal-oxide thin films of WO3 have been prepared by thermal evaporation at a low deposition rate. The material characterization shows that the thin films have stoichiometric composition and the tungsten ions were fully oxidised into W6+. The surface of the WO3 thin films became smoother when the thickness increased. The results show that the deposition of WO3 thin film follows island growth. The flatband voltage of WO3/Si was extracted. The values on n-Si and p-Si were about 0.75 eV and 0 eV, respectively. It was also found that large amounts of negative charges were accumulated at the interface of WO3/n-Si because of electron transfer. (C) 2017 Elsevier B.V. All rights reserved.