The invariance of the initial potential of ZnO xerographic layers with respect to the potential of the corona source, and the increase of the initial potential with increasing layer thickness appear to be a consequence of the dielectric breakdown of small regions of the layer during charging. The variation of initial potential with the layer thickness seems to be a result of a positive space charge in the volume of the layer. This space charge probably comes from normally full electron traps withinkTof the dark Fermi level which are ionized during charging. Typical space‐charge densities are about 1014/cm3.