Structural, photoelectrical and photoluminescence properties of Ta-doped SnO2 monocrystal films grown on MgF2 (110) substrates

Abstract

Epitaxial Ta-doped SnO2 films with Ta concentrations from 0 to 8 at.% have been deposited on MgF2 (110) substrates by the metal-organic chemical vapor deposition (MOCVD) method. The effects of Ta doping on the structural, photoelectrical and photoluminescence (PL) properties of the obtained films were studied in detail. The results showed that the single crystal rutile SnO2 films were obtained and the heteroepitaxial relationship was SnO2 (110) || MgF2 (110) with SnO2 [001] || MgF2 [001]. The highest Hall mobility of 74.2 cm2 V−1 s−1 was achieved for the 5 at.% Ta-doped SnO2 film and the minimum resistivity as low as 2.5 × 10−4 Ω cm was obtained at 6 at.% of Ta-doping. In the visible region, all the obtained films had average transmittances exceeding 87%. As the Ta concentration increased from 0 to 8 at.%, the optical band gap of the films rose from 3.89 to 4.32 eV. The room temperature PL spectra of Ta-doped SnO2 films showed intense green emission, weak violet and yellow emissions. The corresponding PL mechanisms were discussed.