Electrical and Thermal Transport Properties of Bi$_{2}$Sr$_{2}$Co$_{2}$O$_{9-\delta }$ Single Crystals and Thin Films

Layered Bi$_{2}$Sr$_{2}$Co$_{2}$O$_{9-\delta }$ possesses rich physical properties, promising for thermoelectric applications. We have successfully synthesized Bi$_{2}$Sr$_{2}$Co$_{2}$O$_{9-\delta }$ in both single crystal and epitaxial thin film forms by applying various oxygen pressures. We found that their electrical and thermal transport properties are sensitive to the oxygen content, suggesting that the oxidation state of Co plays an important role in thermoelectric properties. Comparison of power factor between single crystals and thin films will be presented.