Optical studies of layered cobaltate NaxCoO2
thin films
Hsiang-Lin Liu
Department of Physics, National Taiwan Normal University, Taipei 116, Taiwan
The sodium cobalt oxide bilayer-hydrate is the first superconductor in cobalt oxide
systems. Like in the case of the cuprates, the phase diagram of sodium cobaltate
encompasses several competing electronic phases, and there are many indications that
the superconducting state is unconventional. Recently, we have successfully
fabricated NaxCoO2 thin films via lateral diffusion of sodium into Co3O4 (111)
epitaxial films (reactive solid-phase epitaxy). The environment of thermal diffusion is
a key to the control of the sodium content in thin films. From the results of x-ray
diffraction and in-plane resistivity, the epitaxial growth and the sodium contents of
these films were identified. In this talk, I will focus on optical spectroscopy, defined
here as the information gained from the absorption, reflection, transmission, or
scattering of electromagnetic radiation, including models which account for, or
interpret, the experimental results of NaxCoO2 thin films.