Nanoprobing Electrical Properties of Organic Semiconductors and Molecular Assemblies

0084404

Frisbie

These projects exploit the atomic force microscope (AFM) to measure electrical potentials and current-voltage characteristics of materials with high spatial resolution. The work focuses on organic semiconductors and self-assembled monolayers (SAMs). The first project, Kelvin Probe Force Microscopy (KPFM) of metal-organic semiconductor interfaces and operating organic field effect transistors (OFETs), employs metal-coated AFM tips to sense surface potentials. Frisbie will use KPFM to measure the contact potential difference (CPD) at metal-organic interfaces to determine the extent of interfacial charge-transfer. He will also use KPFM to map voltage 'drops' in operating OFETs to determine the bottlenecks to electrical transport in these devices. These KPFM studies will quantify the importance of film microstructure and metal-organic interfaces to organic semiconductor transport.

The second project, fabrication and electrical characterization of metal-molecule-metal junctions, will use conducting AFM tips to contact single monolayers of molecules assembled on surfaces. The objective of these studies is to characterize transport in molecules as a function of bonding and functional group architecture.

It is expected that fundamental understanding stemming from this work about the roles of microstructure, metal-organic interfaces, and molecular architecture on transport will impact efforts to improve electronic devices based on molecular films. These studies involve training of graduate students in the areas of organic thin film electronics, transport physics, and scanning probe microscopy, all of which are areas of high interest to industry.