Tailoring of inclined crystal orientation in layered cobaltite thin films for the development of off-diagonal thermoelectric effect

摘要

A highly inclined CoO_2 plane orientation was realized in Ca_xCoO_2 thin films grown on sapphire single crystal substrates. The inclination angle of the CoO_2 plane orientation was controlled by changing the inclination angle of the sapphire(0001) plane with respect to the substrate surface and additionally by introducing an epitaxial buffer layer of hematite. We demonstrate that the highly inclined crystal orientation results in a unique off-diagonal thermoelectric effect with a potential to produce a voltage signal of up to 600 mV along the film in-plane direction by a unit temperature difference along the film out-of-plane direction.