C. Daniel Frisbie Group
Chemical Engineering & Materials Science
University of Minnesota - Twin Cities 		Films & Interfaces,
Molecular Crystals,
Molecular Electronics,
Organic Semiconductors,
Scanning Probe Microscopy

Jeff_Merlo Jeff Merlo
DuPont Corporation
Ph.D. Chemical Engineering, 2005

Field Effect Transport in Organic Semiconductor Films and Nanostructures

My research focuses on correlating microstructure and charge transport in semicrystalline conducting polymers and small molecule organic semiconductors. In the first facet of my research, I use advanced nanofabrication techniques such as electron beam lithography to probe the mobility in sub-micron ordered domains of conducting polymers. The chief goal is to establish the fundamental limit of mobility in these materials and the connection of this limit to structure at the nanoscale.

Nanofibers of regioregular poly(3-hexylthiophene) are my current system of study. Microscopy techniques such as AFM and TEM are employed to characterize the microstructure in this system. Electrical measurements as a function of temperature allow calculation of the activation energy in these polymer nanofibers. From these data, the role of charge trapping and the polymer-dielectric interface are being studied. Fundamental understanding of the relationship between electrical transport and structure in conducting polymers will be gained through these studies.

The second aspect of my research examines charge transport in single grains and single grain boundaries of crystalline organic semiconductors such as pentacene and sexithiophene. By probing charge transport in these systems the limit of mobility in crystalline organic semiconductors can be determined as well as the effect of grain boundaries as a possible bottleneck to transport in thin films.

Publications
"Ambipolar Transport in Heterostructured Organic Thin Film Transistors," Mohapatra, S.; Merlo, J. A.; Holmes, B. T.; Newman, C. R.; Chesterfield, R. J.; Frisbie, C. D.; Ward, M. D., J. Phys. Chem. B (submitted).

"P-Channel Organic Semiconductors Based on Hybrid Acene-Thiophene Molecules for Thin Film Transistor Applications," Merlo, J. A.; Newman, C. R.; Gerlach, C. P.; Kelley, T. W.; Muyres, D. V.; Fritz, S. E.; Toney, M. F.; Frisbie, C. D., J. Amer. Chem. Soc. 2005, 127 3997-4009.

"Field Effect Transport and Trapping in Regioregular Polythiophene Nanofibers," Merlo, J. A.; Frisbie C. D., J. Phys. Chem. B 2004, 108 19169-19179.

"Transport Properties of Single Crystal Tetracene Field Effect Transistors," Newman, C. R.; Chesterfield, R. J.; Merlo, J. A.; Frisbie, C. D., Appl. Phys. Lett. 2004, 85 422-424.

"Field Effect Conductance of Conducting Polymer Nanofibers," Merlo, J. A.; Frisbie, C. D., J. Polym. Sci. Part B: Polym. Phys. 2003, 41 2674-2680.

Frisbie Home Page