Organic semiconductors are of core importance to Organic Thin Film Devices (OLED, OTFT). Research in Molecular Electronics explores the fundamentals of electron transport in transition to nanometer scale assemblies and individual molecules. Our research is geared at the transition between the transport through individual molecules typically measured by Break-Junction and SPM techniques and larger close to macroscopic thin film devices. For this purpose, two different experimental set-ups have been developed.

Electronic Transport in Monolayer Films

Field-effect transistors enable the investigation of charge transport properties of organic semiconductors by gate modulation of the carrier density in the organic semiconductor channel. Very thin channels made of few monolayer (1-2 ML) thin film are used as ultra-sensitive probe for studying the effect of environment (oxygen from air, moisture, etc) and dopant molecules (electron acceptor/donor) on the carrier concentration and mobility.

Fig 1: scheme of a field effect transistor based on organic molecules

Electronic Transport in Self-Assembled Nanostructures

Metallic nanogaps with tunable gap spacing (100 – 1 nm) are obtained by a new manufacturing method [1]. These nanogaps are used as a template for the self-organized growth of pentacene nanorods (combined top-down/bottom-up approach). Temperature dependent electrical transport of the contacted nanorods is investigated. By using different gap spacing, the transition from a diffusive to a ballistic transport regime will give insight into the physical phenomena that govern the electronic transport at the nanometer scale. This research contributes to future applications of organic materials on the nanometer scale.

Fig 2: Nanojunction device made of self-assembled pentacene molecules bridging a 10 nm gap between metallic electrodes.

Reference
[1] Vanoni C., Tsujino S. and Jung T.A., submitted to Nanotechnology (2006)

Contact
C. Vanoni: claudio.vanonipsi.ch
Dr. T.A. Jung: thomas.jungpsi.ch
Dr. S. Tsujino: soichiro.tsujinopsi.ch

Academic partner
Prof. C. Schoenenberger, Nano-Electronics, University of Basel

Financal support:
PSI, NCCR Nanosciences