Mechanisms for current-induced conductivity changes in a conducting polymer

A layer of polyethylene dioxythiophene:polystyrene sulfonic acid (PEDT:PSS) spun onto the surface of an inorganic semiconductor forms a highly asymmetric rectifying junction when a small current is applied and can be permanently open circuited with application of a high current density. This allows the polymer/semiconductor junction to function as a write-once-read-many-times memory element. We use x-ray photoelectron spectroscopy and temperature induced conductivity measurements to study the morphological and chemical changes responsible for the large current-induced conductivity changes. It is found that by applying a large current to the organic-inorganic semiconductor rectifying heterojunction structure AuPEDT:PSSSi, the ratio of PEDT+ to PSS- near the interface changes due to phase segregation in the presence of both high electric field (> 105 Vcm) and temperature. This leads to a decrease in film conductivity by up to six orders of magnitude from its value in the conductive state.