Atmospheric plasma discharge chemical vapor deposition of SnOx thin films using various tin precursors

A series of 0.2–0.6 μm thick SnOx films were deposited onto borosilicate and sodalime silica glass substrates by atmospheric plasma discharge chemical vapor deposition at 80 °C. SnOx films deposited from monobutyltin trichloride contained a large percentage of SnCl2:2H2O, and therefore were partially soluble in water. SnOx coatings deposited from tetrabutyltin were not soluble in water or organic solvents, had good adhesion even at growth rates as high as 2.3 nm/s, had high transparency of ∼ 90% and electrical resistivity of 107 Ω cm. As-grown tin oxide coatings were amorphous with a small concentration of SnO2, SnO and Sn crystalline phases as determined by grazing angle X-ray diffraction and X-ray photoelectron spectroscopy measurements. Upon annealing in air at 600 °C the resistivity of SnOx films decreased to 5–7 Ω cm. Furthermore, optical and X-ray measurements indicated that SnOx was converted into SnO2 (cassiterite) with a direct band gap of 3.66 eV. Annealing of as-grown SnOx films in vacuum at 340 °C led to formation of the p-type conductor SnO/SnOx. The indirect band gap of SnO was calculated from the optical spectra to be 0.3 eV.