Ordering Phenomena in Transition Metal Oxides

Interface Charge Transport in Organic Transistors   

Interface charge transport in small-molecule-based organic semiconductors has recently attracted considerable attentions in physics as well as in applications involving flexible, large-area electronic devices. Here we present our recent studies on transport mechanism at molecular semiconductor interfaces using field-effect transistor (FET) device structures. First we discuss polaron dynamics at channel/insulator interfaces based on field-induced electron spin resonance (ESR) spectroscopy. The motional narrowing effect is clearly demonstrated in the observed field-induced ESR spectra, which reveals a considerably long trapping time and a trap-dominated conduction in pentacene thin-film FETs and rubrene single crystal FETs.

We also discuss issues for electrical contacts at molecular semiconductor interfaces. Particularly we demonstrate that charge injections in organic FETs are improved and enhanced with use of "intermolecular charge-transfer (CT)" that are known to provide rich electronic functionality to organic molecular solids.