Structural and electrical studies on highly conducting spray deposited fluorine and antimony doped SnO2 thin films from SnCl2 precursor

Tin oxide thin films doped with fluorine, antimony and both have been prepared by spray pyrolysis from SnCl2 precursor. The respective deposition temperatures of SnO2:F, SnO2:Sb and SnO2:(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 SnO2:F and SnO2: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 (Rsh) of 5.65 Ω/□ obtained for a SnO2:F sample, is even lower than the values reported for the spray deposited tin oxide thin films prepared from SnCl2 precursor. The resistivity (ρ) and mobility (μ) are in the range of 10−4–10−3 Ω-cm and 7–17.2 cm2 V−1 s−1. The electron density lies between 1.3×1020 and 13.2×1020 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.