Electrical properties of Ta-doped SnO2 thin films epitaxially grown on TiO2 substrate

We report electrical properties of Ta-doped SnO2 (Sn1−xTaxO2) films epitaxially grown on (110) surfaces of rutile TiO2 single crystalline substrates by a pulsed laser deposition method. Due to the large in-plane lattice mismatches (3.0% along [1¯10] and 7.7% along [001]), the films had almost relaxed crystalline structure. With increasing x, electron density was systematically enhanced to undergo the insulator-metal transition between x=0.0004 and 0.004. Sn0.95Ta0.05O2 films exhibited the resistivity as low as 1.1×10−4 Ω cm that is comparable to the lowest value for an epitaxial In2O3 film doped with Sn.