Structural, optical and transport studies of nanocomposite SnOx thin films grown by DC sputter deposition and post-annealing

Abstract

In this paper, we report on the systematic variation in structural, optical and transport properties of SnOx films prepared by DC sputter deposition followed by post-deposition annealing in air for 15 min each, firstly at 200 °C, and subsequently at 250, 275 and 300 °C. The formation of Sn rich SnO crystalline phase with annealing at 200 °C, its increase with annealing at 250 °C due to oxidation of Sn, and its partial decomposition to amorphous SnO2 phase upon annealing at and above 275 °C, were identified by x-ray diffraction and Raman spectroscopy studies. The bandgap value was 2.63 eV for the film with highest SnO crystalline phase obtained with annealing at 250 °C, and it was higher at 2.67 eV and 2.71 eV for films subsequent annealed at 275 °C and 300 °C, respectively. The transmittance of the films in the 400–650 nm wavelength range increased from a minimum of 0.15 to a maximum of 0.82 upon increment in annealing temperature. Rutherford backscattering spectroscopy study revealed an increase of oxygen in the films with annealing. Transport measurements performed on the annealed films show that they exhibit n-type conductivity with resistivity in the 1.05 − 0.01 × 10+1 Ω cm range and a very weak photo-response to visible light. Our results indicate the potential use of the n-type SnOx films as high-resistivity transparent (HRT) buffer layer in flexible solar cells.