Electrical properties and surface morphology of heteroepitaxial-grown tin-doped indium oxide thin films deposited by molecular-beam epitaxy

Heteroepitaxial growth of nondoped indium oxide (IO) and Sn-doped indium oxide (ITO) thin films was carried out on optically polished single-crystalline yttria-stabilized zirconia (YSZ) substrates by molecular-beam epitaxy. The surface morphology of the epitaxial films was analyzed by field-emission-type scanning electron microscopy. The IO and ITO films showed quite different surface morphology, implying that the crystal-growth mechanisms were strongly affected by the Sn doping. The surface migration of In on the (111) plane should be suppressed with increasing Sn concentration, resulting in the relatively large growth rate along the 〈111〉 direction. The epitaxial IO film deposited on YSZ(001) substrate showed very high mobility (μ=86 cm 2 /V s ) and low carrier density (n=3.5×10 18 cm −3 ). Sn doping by 2.6 at. % increased the carrier density by 6.5×10 20 cm −3 , where doping efficiencies were about 81%.