ELECTRONIC-PROPERTIES OF METAL POLY(PYRROLE) JUNCTIONS

In recent years there has been a growing interest in the use of molecu lar organic materials in microelectronic devices, such as polymer diod es, transistors and gas sensors. Conducting polymers form an important class of organic materials that are being investigated as a substitut e for conventional inorganic semiconductor materials. Electrodeposited conducting polymers, such as the pyrrole-based family, have some dist inct advantages in their ease of microdeposition and in situ doping, ' tunable' band-gap and high electronic mobility. In this paper we repor t on the fabrication and properties of novel poly(pyrrole)-tosylate/me tal PPy(pTSA)/metal junctions. Thin (approximately 0.5 mum) PPy(pTSA) films were electrochemically deposited onto small gold electrodes on s ilicon microelectronic substrates. The PPy(pTSA)/Au junction always fo rms an ohmic junction. Low work function metal contacts (e.g. Cu and A g) were either physically evaporated onto the poly(pyrrole) or electro chemically deposited to form the junction. Poor reproducibility was ob served in both types of junction with about half the devices exhibitin g weakly rectifying junctions (ideality factor of about eight). There was no discernible difference in the characteristics of the evaporated and electrodeposited junctions. The electronic characteristics of the junctions were not consistent with conventional Schottky theory; for example, PPy(pTSA)/Ag always showed an ohmic contact. Instead, the poo r stability and general behaviour seems consistent with the formation of an MOS junction following reaction at the interface. Our observatio ns suggest that the development of electrodeposited pyrrole-based micr oelectronic devices is inherently difficult.