Electrical properties of Ta-doped SnO 2 thin films epitaxially grownon TiO 2 substrate

We report electrical properties of Ta-doped SnO 2 ( Sn 1 − x Ta x O 2 ) films epitaxially grown on (110) surfaces of rutile TiO 2 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. Sn 0.95 Ta 0.05 O 2 films exhibited the resistivity as low as 1.1 × 10 − 4 Ω cm that is comparable to the lowest value for an epitaxial In 2 O 3 film doped with Sn.