Improvement of CuAlO2 thin film electrical conduction by the anisotropic conductivity

CuAlO2 thin films with (015) preferential orientation growth have been synthesized on quartz substrates using radio frequency (rf) magnetron sputtering at low temperature. Via the optimized postannealing condition (in N-2 preserved ambient at 900 degrees C for 5 h), the preferential orientation of the films changes from (015) to (001) direction. The use of a higher conductivity at the ab plane of CuAlO2 compared with that along the c axis, reduces the resistivity of the film at room temperature to 37 Omega.cm from that of the as-deposited, 4.62 x 10(4) Omega.cm. The positive Hall coefficient (+183.6 cm(3)/C) and the large mobility (4.07 cm(2)/V.s) suggest that CuAlO2 thin films are p-type semiconductors with good conduction path. The temperature dependence of conductivity indicates that CuAlO2 thin films obey a thermal-activation theory when the temperature is above 190 K, but below 185 K a two-dimension variable-range hopping mechanism becomes dominant.