Origin of the Bistability in an Organic Device with a Nano-Scaled Layer

Abstract

Bistability is often observed in thin organic materials, but it is not a typical property of the bulk state. The origin of that bistability was investigated in a 30-nm Polyvinylcarbazole(PVK) device. This device was a reproducible write-once-read-many memory, which changed from the OFF to the ON state at around 2 V in the first forward bias. Its conductivity in the ON state was similar to that of a poor metal, but some of the devices shifted their electric properties into reversible bistability with a small ON/OFF ratio or an open circuit with a, low leakage current during repeated bias scans. The initial change in the conductance was caused by the field-induced metal filament, which originated from the deposition of the top electrode. Because the repeating bias scan led to the oxidation of the filament by joule heating, the device changed into a reversible bistability due to non-stoichiometric aluminum oxide or into an open circuit due to alumina.