Biography

Dr. Geohegan is currently a Research Professor in the Department of Materials Science and Engineering at the University of Tennessee where he continues to develop and apply real-time diagnostics for the fundamental understanding of growth mechanisms of nanomaterials, thin films, and atomically-thin 2D materials. He is a highly-cited researcher with over 330 peer-reviewed publications and was recognized in 2011 as a Fellow of the American Physical Society for his pioneering work in understanding and controlling nonequilibrium growth processes of thin films and nanomaterials through real-time laser spectroscopy, imaging, and plasma diagnostic investigations.

He earned his Ph.D. in Physics at the University of Illinois in Urbana-Champaign in 1987 with Prof. J. Gary Eden on experimental atomic and molecular laser photophysics of excimer molecules. After a postdoctoral appointment with Prof. Eden on laser chemical vapor deposition, he was hired as a research staff member in 1988 in the Solid State Division at Oak Ridge National Laboratory in the research group of Dr. Douglas H. Lowndes. There he co-developed the first pulsed laser deposition (PLD) system at ORNL for the growth of high-Tc superconductor thin films, and utilized his gas phase laser spectroscopy training to understand the unique features of pulsed laser ablation plasmas by coordinating high-speed ICCD photography, ion probe analysis, and optical spectroscopy diagnostics during film growth by PLD, working on the growth of amorphous diamond and luminescent porous silicon.

At ORNL his attention shifted to nanomaterials when he worked with Dr. Alex Puretzky in Prof. Bob Compton’s seminal LDRD on carbon fullerenes focusing on understanding and controlling their synthesis by laser ablation. This led to in situ measurements and growth models of how single-wall carbon nanotubes grow by laser ablation at high temperatures, and later, in situ diagnostics and growth models for carbon nanotube, carbon nanohorn, and graphene growth by chemical vapor deposition (CVD). These synthesis and optical characterization capabilities were integrated into Center for Nanophase Materials Sciences (CNMS) at ORNL which opened in 2006 he was a Group Leader of the Functional Hybrid Nanomaterials group, Distinguished Scientist, and Distinguished Inventor. More recently, work has focused on the growth of atomically-thin 2D materials by PLD, and their doping by controlling the kinetic energy of PLD plasmas for the growth of Janus monolayer transition metal dichalcogenides.

Education

PhD, Physics, University of Illinois, Urbana-Champaign, 1987

Professional Service

• Co-chair and organizing committee of focused conferences on synthesis science, including Co-chair (2004–2021) of SPIE Photonics West ‘Synthesis and Photonics of Nanoscale Materials’ Symposium, International Conference on Laser Ablation (COLA) Advisory Committee, “Distinguished Service Award” (2009), Guadalupe Workshop on SWCNT Growth Mechanisms Co-Chair (2011; 2013; 2015; 2019; 2021), Spring Materials Research Society Symposium “Co-Chair” (2008; 2010),past chair of GRC on Laser Interactions with Materials.
• Reviewer for Peer-Reviewed Journals: Nature Materials, Nature Communications, Nano Letters, ACS Nano, Small, Journal of Physical Chemistry C, Applied Physics Letters, Journal of Applied Physics, Applied Physics A, Applied Physics B, Carbon, Journal of Nanophotonics, etc

Awards and Recognitions

• UT-Battelle Outstanding Scholarly Output Award (2020)
• ORNL Distinguished Inventor Award (2018)
• American Physical Society Fellow (2011)

Research Publications

A full list of publications is available on Google Scholar.