Photovoltage characterization of CuAlO2 crystallites

The delafossite phase of CuAlO2 has been prepared by ion exchange reaction at 475degreesC. The samples were characterized by x-ray diffraction, transmission electron microscopy, electron diffraction, transient and spectral photovoltage (PV), and diffuse reflectance spectroscopy. The produced CuAlO2 crystallites are p-type and of high electronic quality, i.e., no electronic transitions induced by deep states in the forbidden gap have been observed by PV. The temperature dependence of the optical band gap of CuAlO2 was measured between 80 and 600 K. The band gap of CuAlO2 approximated to 0 K amounts to 3.61 eV. The quenching of the PV signal is thermally activated with an activation energy of 1.8 eV. (C) 2004 American Institute of Physics.