Structural and electrical studies on highly conducting spray deposited fluorine and antimony doped SnO 2 thin films from SnCl 2 precursor

Abstract

Tin oxide thin films doped with fluorine, antimony and both have been prepared by spray pyrolysis from SnCl 2 precursor. The respective deposition temperatures of SnO 2:F, SnO 2:Sb and SnO 2:(F+Sb) are 400 °C, 350 °C and 375 °C. The as-prepared films are polycrystalline with a tetragonal crystal structure. The lattice parameter values are not changed by the addition of dopants. The films are preferentially oriented along the (200) direction. The grain sizes vary between 200 and 650 Å. The films have moderate optical transmission (up to 70% at 800 nm) and the calculated reflectivity in the infra-red region is in the range of 88–95%. The figure of merit (φ) values of SnO 2:F and SnO 2:Sb samples are 2.5×10 −3 (Ω) −1 and 1.4×10 −4 (Ω) −1, respectively. The films are heavily doped, degenerate and exhibit n-type electrical conductivity. The lowest sheet resistance ( R sh) of 5.65 Ω/□ obtained for a SnO 2:F sample, is even lower than the values reported for the spray deposited tin oxide thin films prepared from SnCl 2 precursor. The resistivity (ρ) and mobility (μ) are in the range of 10 −4–10 −3 Ω-cm and 7–17.2 cm 2 V −1 s −1. The electron density lies between 1.3×10 20 and 13.2×10 20 cm −3. A thorough electrical investigation reveals that the film's conductivity depends only on carrier concentration. It is found that ionised impurity scattering is the dominant mechanism, which limits the mobility of the carriers.