Kelvin probe force microscopy of defects in ZnO nanocrystals associated with emission at 3.31 eV

The surface potential variations on ZnO nanocrystal surfaces were investigated by using Kelvin probe force microscopy. It was found that the nanocrystal surface contains randomly distributed circular pits with a diameter of ∼100nm and a depth of ∼30 nm and that the surface potential within the pits is lower than that in the vicinity of the pits. We discuss the correlation between the observed pits and speck-like defects on a ZnO nanocrystal surface associated with the emission at 3.31 eV. We suggest that the reduced surface potential is caused by the local acceptor-like states concentrated near the structural defects.