Anisotropic carrier transport properties in layered cobaltate epitaxial films grown by reactive solid-phase epitaxy

作者：Sugiura Kenji^*; Ohta Hiromichi; Nakagawa Shin ichi; Huang Rong; Ikuhara Yuichi; Nomura Kenji; Hosono Hideo; Koumoto Kunihito

来源：Applied Physics Letters, 2009, 94(15): 152105.

DOI：10.1063/1.3119631

• electrical resistivity
• scanning electron microscopy
• Seebeck effect
• semiconductor epitaxial layers
• semiconductor materials
• sodium compounds
• transmission electron microscopy

Herein we report the anisotropic carrier transport properties of a layered cobaltate, NaxCoO2 epitaxial film grown on the m-plane of an alpha-Al2O3 substrate using reactive solid-phase epitaxy. Scanning and transmission electron microscopy analyses revealed that NaxCoO2 was heteroepitaxially grown with the CoO2 conducting planes inclined by similar to 43 degrees against the alpha-Al2O3 substrate surface. The electrical resistivity parallel to the CoO2 planes was similar to 1/5 of the perpendicular one, but the parallel Seebeck coefficient was about twice as large as the perpendicular one. Hence, a higher thermoelectric efficiency in the cobaltates can be obtained within the CoO2 planes.

• 出版日期2009-4-13