•Highly oriented SnO2 film without twinning was deposited at 700 °C.•Substrate temperature strongly affected the surface morphology of SnO2 films.•Electrical properties were studied as a function of substrate temperature.Tin oxide (SnO2) films have been grown on r-cut sapphire substrates by metalorganic chemical vapor deposition (MOCVD). The substrate temperature dependent structural and electrical properties of SnO2 films were investigated. It was found that the films deposited at lower temperatures were polycrystalline while the highly oriented growth occurred above 600 °C. Especially, high-quality SnO2 film with no (101) twin structure was obtained at 700 °C. Scanning electron microscopy showed that the surface morphology was significantly affected by the substrate temperature. A tile-like surface was observed for the film grown at 700 °C. The change in electrical properties for the SnO2 films was associated with the various structures at different substrate temperatures.

Gallium oxide (Ga2O3) films were deposited on MgO (100) substrates by metalorganic vapor phase epitaxy. Structure analyses showed that the films deposited at 550–700 °C were epitaxial β-Ga2O3 films with an out of plane relationship of β-Ga2O3(100)||MgO(100). The film deposited at 650 °C showed the best crystallinity and the microstructure of the film was investigated by high resolution transmission electron microscopy. A theoretical model of the growth mechanism was proposed and the in-plane epitaxial relationship was given to be β-Ga2O3[001]||MgO<011>. A four-domain structure inside the epitaxial film was clarified. The β-Ga2O3 film deposited at 650 °C showed an absolute average transmittance of 95.9% in the ultraviolet and visible range, which had an optical band gap of 4.87 eV.Highlights► Beta Ga2O3 epitaxial films were deposited on MgO(100) substrate. ► A theoretical model of the growth mechanism was proposed. ► The transmittance of the film in the ultraviolet and visible region exceeded 95.9%.

Epitaxial tin oxide (SnO2) thin films have been prepared on MgO (100) substrates at 500–600 °C by metalorganic chemical vapor deposition method. Structural and optical properties of the films have been investigated in detail. The obtained films were pure SnO2 with the tetragonal rutile structure. An in-plane orientation relationship of SnO2 (110) [010]//MgO (200) [110] between the film and substrate was determined. Two variant structure of SnO2 were analyzed. The structure of the film deposited at 600 °C was investigated by high-resolution transmission electron microscopy, and an epitaxial structure was observed. The absolute average transmittance of the SnO2 film at 600 °C in the visible range exceeded 90%. The optical band gap of the film was about 3.93 eV.Highlights► Epitaxial SnO2 films were prepared on MgO by MOCVD. ► The film presented an epitaxial relationship of SnO2 (110) [010]//MgO (200) [110]. ► The average transmittance of the SnO2 sample was over 80% in the visible range.