Substrate-induced anisotropy of c-axis textured Na_xCoO_2 thin films

摘要

N_axCoO_2 [x = 0.51, 0.54, and 0.59] thin films have been grown on SrTiO_3 (100)-oriented single crystals with a 5° vicinal cut towards [010] by pulsed laser deposition. We analysed the films by X-ray diffractometry, atomic force microscopy (AFM), and dc-transport measurements. X-ray diffraction patterns of the films show single phase and c-axis textured growth with the film plane closely aligned to the [001]-direction of 5° miscut SrTiO_3 (001) substrates. In addition to the structural analysis of these films we performed transport measurements along and perpendicular to the substrate tilt direction and determined the resistivity anisotropy as a function of temperature. The results enable the development of a strategy for the fabrication of Na_xCoO_2 based thermoelectric thin film devices.