C. Daniel Frisbie Group
Chemical Engineering & Materials Science
University of Minnesota - Twin Cities
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Films & Interfaces,
Molecular Crystals,
Molecular Electronics,
Organic Semiconductors,
Scanning Probe Microscopy
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Paul Pesavento
Hutchinson Technology, Inc.
Ph.D. Materials Science, 2005
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Field Effect Electrical Characterization of
Thin-Film And Single Crystal Molecular Organic Semiconductors
My research centers on molecular, morphological, and electrical properties of molecular organic semiconductors in an attempt to understand the electronic processes occurring within. Morphology and crystal packing of polycrystalline thin-films and single crystalline materials are examined via atomic force microscopy and x-ray diffraction (XRD) techniques for their effect on electrical properties. Electrical characteristics of both thin-films and single crystals are characterized via current-voltage measurements in a two- and three-terminal fashion, i.e. in space charge limited and field-effect geometries. Time-of-flight and temperature-dependent measurements are also performed. In particular, charge carrier mobility and threshold voltage are studied for dependence on molecular and crystal structure, morphology, temperature, gate field, and trap concentration. Additional probes are used to examine and remove contact resistance dependence from the electrical measurements. Each material studied is also tested for ambipolar operation and dopant sensitivity. Since only ultra-high quality single crystals and thin-films have proven ambipolar, the ability to conduct both holes and electrons is a measure of the amount of disorder present within a film or single crystal. Sensitivity to possible atmospheric dopants and others intentionally introduced is examined via electrical characterization of each material in air, under gaseous dopant atmospheres, and vacuum.
Publications
"Gated Four-Probe Measurements on Pentacene Thin-Film Transistors: Contact Resistance as a Function of Gate Voltage and Temperature," Pesavento, P. V.; Chesterfield, R. J.; Newman, C. R.; Frisbie, C. D., J. Appl. Phys. 2004, 96 (12) 7312-7324.
"Surface Potential Profiling and Contact Resistance Measurements on Operating Pentacene Thin-Film Transistors by Kelvin Probe Force Microscopy," Puntambekar, K. P.; Pesavento, P. V.; Frisbie, C. D., Appl. Phys. Lett. 2003, 83 (26) 5539-5541.
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