Crystal growth and transport properties of CuAlO2 single crystal

The transport properties of the delafossite CuAlO2 single crystal, grown by the flux method, are confined in (a)[AlO2] layers extending in the (001) plans. The dielectric properties are measured up to 490 K in the frequency range (10(2)-10(5) Hz). The small variation of the dielectric loss tan(delta) is attributed to the wide space charge region. The linear plot log (conductivity) vs. 1000/T follows an Arrhenius type law and the results are discussed in terms of electron hopping among localized states. The activation energy (0.18 eV) gives an effective mass of 16m (0) indicating that the levels in the vicinity of the Fermi level are strongly localized. Hence, the increase of the conductivity (sigma) results from a thermal activation of the mobility (mu(300 K) = 1.2 x 10(-5) cm(-2) V-1 s(-1)). The sign of hole like small polarons is that of p type carriers originating from oxygen intercalation. The thermopower is little temperature dependent and characteristic of non degenerate conductivity with a low holes concentration and a large concentration of surface states within the gap region.