UV–vis transparent conducting Ta-doped SnO2 epitaxial films grown by metal-organic chemical vapor deposition

Tantalum (Ta)-doped SnO2 films with different Ta concentrations have been deposited on α-Al2O3 (012) substrates by the metal organic chemical vapor deposition (MOCVD) method at 620 °C. Structural, electrical and optical properties of the obtained films have been investigated in detail. Structural analyses revealed that all the obtained films were rutile SnO2 growing along SnO2 [101] orientation. The 4% Ta-doped SnO2 film exhibited the best crystal quality and the in-plane epitaxial relationship between the film and substrate was SnO2 [010]//Al2O3 [110]. The highest Hall mobility of 58.1 cm2 V−1 s−1 was achieved for the 4 at.% Ta-doped SnO2 film and the minimum resistivity as low as 4.0 × 10-4 Ω cm was obtained at 6 at.% of Ta doping concentration. In the visible light region, all the obtained films showed average transmittances exceeding 88%. With Ta concentration increasing from 0 to 8 at.%, the transparent range of the films extended to the UV-B light region (280–320 nm), while the optical band gap of the films rose from 3.96 to 4.30 eV.