Epitaxial growth of CuScO2 thin films on sapphire a-plane substrates by pulsed laser deposition -: art. no. 083535

An epitaxial film of CuScO2, a transparent oxide semiconductor with a delafossite structure, was grown on an alpha-Al2O3(11(2) over bar 0) substrate by a pulsed laser deposition method using a single-phase Cu2Sc2O delta target. A two-dimensional x-ray reciprocal space mapping measurement revealed that the film was single phase with a rhombohedral crystal structure. The film showed six-fold rotational symmetry in the basal plane, indicating that the film had a twinned domain structure. The epitaxial growth of CuScO2[3R](0001) thin films on alpha-Al2O3(11(2) over bar 0) substrates is caused by the uniaxial locked epitaxy mechanism along the <<(1)over bar2<(1)over bar 0>> direction of the film, and the orientation relationships of the film with respect to the substrate were CuScO2[3R](0001)//alpha-Al2O3(11(2) over bar 0) and CuScO2[3R][(1) over bar2 (1) over bar 0]//alpha-Al2O3[8(8) over bar 01]. The optical transmittance of the film was larger than 65% in the visible/near-infrared regions, while the energy gap for direct allowed transition was estimated as 3.7 eV. The resistivity of the film, 9.3x10(6) Omega cm at room temperature, significantly decreased to 4.0 Omega cm after both substituting Mg2+ ions for Sc3+ and intercalating excess oxygen. The Mg-doped CuScO2+X(0001) thin film showed optical transmittance of larger than 65% in the visible region, and the Seebeck coefficient was positive, indicating a p-type conductivity. (C) 2005 American Institute of Physics.