Monte Carlo modelling of carrier transport within amorphous materials used in the electrophotography process

• Main Author: Elmer, S. J.
• Published: Swansea University 1995
• Subjects: 537.622
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636793

Monte Carlo techniques have been applied to the field of electrophotography in order to simulate a variety of xerographic dark discharge mechanisms. The work is divided into two sections, each of which concentrates on a particular discharge mechanism. The first is concerned with the transport of surface carriers that drift through the bulk of a sample under the influence of a local internal field (Surface Injection model). Simulations were performed for both trap-free carrier transport and trap-limited band transport in which the trapping centres were distributed over a range of energies. Results for these simulations were found to be in agreement with both the experimental and the theoretical findings of other workers. The surface injection model was also used to account for the cross-over effect observed in xerographic dark decay experiments performed upon polyethylene photoconductors. It was found that the field dependent partial injection of carriers from the sample surface accounted for such a phenomenon. The second part of this work concentrates on the xerographic dark decay associated with the build up of thermally generated charge in the bulk (Bulk Generation model). A bipolar bulk generation (BBG) model was suggested in which both carrier types generated within the bulk are mobile. The results from the BBG simulations produce a dark decay that occurs within a continuous time regime. Such a feature is found to occur within experimental dark decays within <I>a</I>-Si:H and <I>a</I>-Si<SUB>1-x</SUB>C<SUB>x</SUB>:H photoreceptors. It was also shown that the BBG model possessed the same thickness and initial surface charge dependencies as found experimentally. Therefore, it was suggested that dark discharge within <I>a</I>-Si:H and <I>a</I>-Si<SUB>1-x</SUB>C<SUB>x</SUB>:H occurs due to the BBG mechanism.