Electrical and optical properties of tin-doped CdO films deposited by atmospheric metalorganic chemical vapor deposition

Abstract

Highly conductive and transparent tin-doped CdO:Sn were deposited via atmospheric metalorganic chemical vapor deposition. Dimethylcadmium (DMCd), tetramethyltin (TMT), and O 2 were used to deposit the CdO:Sn films. The structural, electrical, and optical properties of the fabricated films were influenced by the partial pressures of DMCd and TMT, substrate temperature, film thickness, and annealing conditions. A sheet resistance of 14–17 Ω/sq was obtained for as-deposited CdO:Sn films with a thickness of 120–150 nm. The high conductivity of the films was mainly due to their high carrier concentration (2–3×10 21/cm 3) and moderate mobility (12–13 cm 2/V s). The transmission of the films in the visible range was high (80–95%) and shifted towards the blue region due to the Moss-Burstein (M-B) effect. The films exhibited direct and indirect band-to-band transitions, which corresponded to optical bandgaps of ∼3.0 and ∼2.5 eV, respectively. The electro-optical properties of as-deposited CdO:Sn films were further improved by post-deposition annealing. A resistivity value of 1.4–1.6×10 −4 Ω cm has been obtained after annealing in He and H 2 ambients, which is the lowest value ever reported for CdO films.