Reciprocity Failure in ZnO-Binder Systems

Paper presented at a symposium on Electrophotography organized by the Science committee of The Royal Photographic Society on ]2-17 September 1976 in Cambridge.

Abstract

In a recent publication [J. Phot. Sci. 23, 193 (1975)] the electrical behaviour of ZnO-binder layers has been studied on a model system, in which an insulator layer up to 5 gm thick, representing a binder, was interpersed between the ZnO-layer proper and the conducting base. Surprisingly, provided the time of exposure is sufficiently short, such double layers (DLs) will discharge completely: the ZnO acts as an “injecting electrode”, and the charges then traverse the insulator. The critical role in the discharge of DLs is played by the interface between ZnO and insulator; here surface states are assumed to act as recombination centres impeding transfer of charges into the insulator, details of which are described by assuming that a Schottky barrier exists in the insulator along the interface.

Reciprocity failure (RF) data for ZnO systems are important characteristics in checking the validity of the model. Motion of charge carriers in commercial ZnO layers shows little RF. The discharge into the insulator sutlers from RF at low and high intensities. If in a ZnO-layer the binder/ZnO ratio is increased, its RF is similar to that of a DL. There is strong indication that even in the conventional Zno layers, charge transport through the binder is an important feature of the discharge process.

The model for the discharge of a DL has been developed further. For exposures at very high intensities discharge through the insulator seems to be eased by a Poole-Frenkel phenomenon in a “high-field” situation.

Notes

Paper presented at a symposium on Electrophotography organized by the Science committee of The Royal Photographic Society on ]2-17 September 1976 in Cambridge.