Characterization of SnO2 obtained from the thermal oxidation of vacuum evaporated Sn thin films

• 50 nm thick thermal evaporated tin films were annealed at 600 °C in air.
• The transformation from Sn to SnO2 was direct.
• The thickness of the oxidized films increases with the annealing time.
• The energy band gap decreases with the annealing time.
• The electrical resistivity decreases with the annealing time.

Tin oxide has been prepared by thermal oxidation of evaporated tin thin films onto pyrex glass substrates. Films oxidation was achieved in air at a temperature of 600 °C with varied duration from 20min to 3 h. Structural, optical and electrical properties of the films were characterized by means of X-ray diffraction, UV–vis spectroscopy and electrical resistivity measurements respectively. The X-ray analysis revealed the transformation of Sn into SnO2 with preferential orientation along (101) plans. No intermediate phases such as SnO and Sn3O4 were evidenced. It was also found that the SnO2 crystallites orientation changed with the annealing time due to the strain energy effect. Both band gap energy and electrical resistivity decrease with annealing time due to the crystalline quality improvement and films densification. We have noticed that oxidation at 600 °C for 3 h leads to transparent and conductive films with suitable properties for photovoltaic applications.