Mist Chemical Vapor Deposition of Single-Phase Metastable Rhombohedral Indium Tin Oxide Epitaxial Thin Films with High Electrical Conductivity and Transparency on Various α-Al2O3 Substrates

Metastable rhombohedral-structured indium tin oxide (rh-ITO) epitaxial films were successfully grown on c -, a -, m -, and r -plane α-Al 2 O 3 substrates with α-Fe 2 O 3 buffer layers using mist chemical vapor deposition. X-ray diffraction measurements showed the growth of rh-ITO epitaxial films with various orientations on the correspondingly oriented substrates with buffer layers. The electron carrier concentrations of the rh-ITO reached (3.8–5.1) × 10 20 cm –3 with Sn impurity doping. Optical transmittance tests showed that the rh-ITO thin films were highly transparent to visible light. The results suggested that the rh-ITO thin films featured both high electrical conductivity and high optical transparency. The band gaps and band gap shifts by the Burstein–Moss effect on the various α-Al 2 O 3 substrates showed different orientation-dependent values. The demonstrated epitaxial rh-ITO thin films with various orientations permit the physical characterization of rare rh-ITO thin films.