Nature of microscopic electrical defects in organic photoreceptors

Abstract

A recently described scanning stylus instrument1 has been used to investigate the electrical properties of individual microscopic electrical defects in organic xerographic photoreceptors. Using a shielded scanning stylus with an effective diameter of 85 pm we have mapped the shape of individual microscopic electrical defects with 5 im resolution and measu red thei r cu rrent-voltage characteristics. H ig h resolution ma ps reprod uced the shape of the stylus indicating that the underlying defect is much smaller than the stylus size. The observed current-voltage characteristics were approximately quadratic in the applied voltage and the currents were basically constant on the time scale of tens of seconds. This observation is an indication of charge injection from the substrate and space charge limited (SCL) currentflow. The magnitude ofthe current enables an estimate of the upper limit of the size of the injecting spot of about 4 pm. This conclusion is derived on the basis of one dimensional SCL current flow and the argument is presented which indicates thatthe defects may be much smaller, possibly point-like in nature.