Charge transport in grain size tuned CuO nanocrystal films

CuO nanocrystal (NC) films of different grain sizes were synthesized through the oxidation of Cu films deposited by controlling the supersaturation in the deposition chamber. The films were characterized by XRD, HRTEM, AFM and optical absorption measurements. Charge transport through the films was investigated by measuring the grain size dependent D C electrical conductivity at different temperatures. The conductivity increased and activation energy for conduction decreased with increase in the size of the primary grains of the films. The charge transport through the NC films was explained considering the films to be equivalent to films of primary CuO NCs made up of a core in which the charge carriers were confined and a surrounding grain boundary region (shell) through which charge transport was not hindered by any potential barrier, with the shells of the primary particles merged together so that the there was no inter particle spacing.