Twinned domains in epitaxial ZnO/SnO2-cosubstituted In2O3 thin films

Zn0.3In1.4Sn0.3O3−δ (ZITO) thin films were grown by computer-controlled pulsed laser deposition (PLD) on (0 0 0 1) Al2O3 substrate. Cross-section and plan-view transmission electron microscopy (TEM) revealed that the ZITO films were composed of twin-related domains with their (2 2 2) planes parallel to (0 0 0 1) planes of the Al2O3 substrate. ZITO {55¯0} planes fitted well to Al2O3{33¯00} planes with a lattice mismatch of approximately 2.8%. Remarkable enhancement of electrical conductivity, about one order of magnitude higher than that of bulk ZITO, was found. The formation of twin-related domains and its effects on electrical and optical properties of ZITO films were also discussed.