Large Polarons Photodoped in Pure CuO

Hall mobility µ H of photocarriers in pure CuO refined by floating zone melting (FZ) method has been studied by adopting a pulsed technique for photoconductivity measurements between T =25 K and 110 K. Dominant photocarriers turn out to be positive holes. Value of µ H of holes increases with decreasing T and reaches 8×10 3 cm 2 V -1 s -1 at 25 K. Scattering mechanisms of photocarriers are due to the high-frequency LO-phonon, acoustical phonon and neutral impurity. The experimental results on the temperature dependence and the absolute value of µ H ( T ) clearly indicate that a relatively wide valence band may exist in CuO, where large polarons are mobile.