Measuring Impact of Light on the Resistance of Non-Doped ZnO Films

This paper demonstrates the significant impact of light on non-doped ZnO films during resistance measurement. A very long time constant of the order of 103 sec is observed. Based on the wave-length dependence of the charging and discharging time constant, possible physical mechanisms are discussed. It is suggested that the energy offset between the top electrode and ZnO film and the charged grain boundaries are responsible for the long time constant. In addition, the paper addresses the possible physical image of defects around the grain boundary and the film surface.