Joint Associate Professor
Dr. Fowlkes is currently a scientific staff member at the Center for Nanophase Materials Sciences located at Oak Ridge National Laboratory. He is a member of the Nanofabrication Research Laboratory research group at the Center for Nanophase Materials Sciences. The Nanofabrication Research Laboratory houses a 10,000 ft2 of class 100/1000 clean room space for carrying out material modification using advanced lithographic, etching, thin–film deposition, and characterization tools. Dr. Fowlkes has authored or co-authored over 100 refereed journal articles.
Charged Particle Beam-Induced, Direct-Write Deposition/Etching Nanoscale direct-write assembly methods, such as focused particle beam processing, require precise understanding and control of the relevant electron/ion–vapor precursor–solid interactions where energy beams on the order of 1–10 nm dictate the assembly/removal of material at the confluence of the particle beam, adsorbed precursor and substrate. We determine precursor–substrate interaction parameters relevant for the electron/ion beam induced deposition methods through a combination of experiments and simulations. Monte Carlo simulations of the electron–substrate interaction are combined with finite difference simulations of precursor–substrate interactions to unravel the parameters by fitting to experimental results.
Self and Directed Assembly of Thin, Liquid Metallic Films Physical vapor deposition combined with nanolithography methods are used to deposit metallic materials with highly non-equilibrium shapes. Capillary, inertial and viscous forces dictate the mass transport of the metal once liquefied. The initial shape of the metallic feature is used to harness liquid surface instabilities for the self-assembly of metallic nanoparticles. Pulsed laser irradiation is used to liquefy the metal features where rapid heating and cooling rates and nanosecond melt lifetimes are achievable. Directed assembly is possible by imposing periodic fluctuations onto the initial metal geometry which translates into highly precise arrays of metallic nanoparticles/nanocaps.
Ph.D., The University of Tennessee: Laser–Induced Nanostructures in Silicon
International Society for Optics and Photonics (SPIE)
American Vacuum Society (AVS)
American Chemical Society (ACS)
J. D. Fowlkes, N. A. Roberts, Y. Wu., J. A. Diez, A. G. Gonzalez, C. Hartnett, K. Mahady, S. Afkhami, L. Kondic and P. D. Rack, “Hierarchical nanoparticle ensembles synthesized by liquid phase directed self–assembly”, Nano Letters 14, 774 (2014)
J. D. Fowlkes and P. C. Collier, “Single-molecule mobility in confined and crowded femtoliter chambers”, Lab on a Chip 13, 877 (2013)
J. D. Fowlkes, L. Kondic, J. A. Diez, A. G. Gonzalez, Y. Wu, N. A. Roberts, C. E. McCold and P. D. Rack, “Parallel assembly of particles and wires on substrates by dictating instability evolution in liquid metal films”, Nanoscale 4, 7376 (2012)
J. D. Fowlkes, S. Horton, M. Fuentes–Cabrera and P. D. Rack, “Signatures of the Rayleigh–Plateau Instability Revealed by Imposing Synthetic Perturbations on Nanometer–Sized Liquid Metals on Substrates”, Angewandte Chemie International Edition 51, 8768 (2012)
J. D. Fowlkes, L. Kondic, J. Diez, Y. Wu and P. D. Rack, “Self–Assembly versus Directed Assembly of Nanoparticles via Pulsed Laser Induced Dewetting of Patterned Metal Films”, Nano Letters 11, 2478 (2011)