Ph.D. Materials Science (Electronic Materials); Massachusetts Institute of Technology, 1992
B.S. Physics; Colorado State University, 1983
Department of Materials Science & Engineering
University of Virginia
PO Box 400745
395 McCormick Road
Charlottesville, VA 22904-4745
Office: Wilsdorf Hall Room 122
My research engages many aspects of thin film growth, with a current focus on self-assembly at the nanoscale. Film growth continues to be a fascinating and important area of research - fascinating because of our ability to grow novel structures far from thermodynamic equilibrium by a variety of processing techniques with exquisite control, and important for the vast range of current and potential applications that employ thin films. I define "thin films" rather broadly, from the traditional two-dimensional layer-on-a-substrate, to supported arrays of quantum dots, nanorods and nanotubes. My work takes a physical metallurgist's view of electronic materials, with an emphasis on the interaction of stress, structure and surface morphology. As my interests in the fundamental materials science of nanostructures continues to grow, so too does my interest in seeing whether useful new functionalities can be achieved using the novel properties of nanostructured materials.
My central research effort is on heteroepitaxial self-assembly of nanostructures in GeSi strain-layers grown on Si (001) substrates. Alloying Ge and Si alloys allow us to take advantage of elastic strain and bandgap engineering techniques to create high performance devices, similar to III-V technology, but using Si-based materials that dominate the semiconductor industry. I employ MBE growth, combined with in situ diagnostics, to probe the detailed evolution of quantum nanostructures. My recent research manipulates the kinetics of MBE growth to produce unusual metastable structures. In particular, we've learned how to self-assemble "quantum dot molecules" (QDMs) - symmetric assemblies consisting of four proximal quantum dots that are elastically bound by a central pit in the epilayer. We're investigating pit nucleation, size selection, compositional inhomogeneities, and how to deterministically direct self-assembly using precision patterning with a focused ion beam. We've also begun to explore whether QDMs can exhibit logic-state and single-electron transistor behavior, in the scheme known as quantum cellular automata - a new approach that could keep computer CPU's on the Moore's Law curve beyond the inevitable end of CMOS-based logic. Our ultimate goal is to gain a deep scientific understanding of how QDMs self-assemble, and to employ this understanding to tailor useful structures for nanologic applications.
Professonal Experience and Memberships
Associate Professor, Dept. of Materials Science and Engineering, UVa
1994-2006: Member of the Technical Staff, Sandia National Labs
1992-1994: Post-doctoral member of the Technical Staff, Sandia National Labs
1984-86: Associate Engineer, IBM Thomas Watson Research Center
Honors and Awards
Chair of the Materials Research Society Public Outreach Committee, 2005-current
Elected to Materials Research Society Board of Directors, 2002-2004.
Co-Chair of the Materials Research Society Fall Meeting, 2001.
Member of team winning the DOE Basic Energy Sciences Award for Outstanding Sustained Research in Metallurgy and Ceramics, 1994.
AT&T Bell Labs Graduate Fellowship, 1990-1992.
BEYOND THE HETEROEPITAXIAL QUANTUM DOT: SELF-ASSEMBLING COMPLEX NANOSTRUCTURES CONTROLLED BY STRAIN AND GROWTH KINETICS, J. L. Gray, R. Hull, Chi-Hang Lam, P. Sutter, J. Means, and J. A. Floro, Phys. Rev. B 72, 155323 (2005).
KINETIC SIZE SELECTION MECHANISMS IN HETEROEPITAXIAL QUANTUM DOT MOLECULES, J. L. Gray, N. Singh, D. M. Elzey, R. Hull, and J. A. Floro, Phys. Rev. Lett. 92, 135504 (2004).
MISFIT DISLOCATION FORMATION IN THE AlGaN/GaN HETEROINTERFACE, J.A. Floro, D. M. Follstaedt, P. Provencio, S. J. Hearne, and S. R. Lee, J. Appl. Phys. 96, 7087 (2004).
THE ORIGINS OF GROWTH STRESSES IN AMORPHOUS SEMICONDUCTOR THIN FILMS, J. A. Floro, P. G. Kotula, S. C. Seel, and D. J. Srolovitz, Phys. Rev. Lett. 91, 096101 (2003).
THE DYNAMIC COMPETITION BETWEEN STRESS GENERATION AND RELAXATION MECHANISMS DURING VOLMER-WBER THIN FILM GROWTH, J. A. Floro, S. J. Hearne, J. A. Hunter, P. Kotula, E. Chason, S. C. Seel, and C. V. Thompson, J. Appl. Phys. 89, 4886 (2001).
CURVATURE-BASED TECHNIQUES FOR REAL-TIME STRESS MEASUREMENT DURING THIN FILM GROWTH, Jerrold A. Floro and Eric Chason, in In Situ and Real Time Characterization of Thin Films, Orlando Auciello and Alan R. Krauss, eds. (John Wiley and Sons, NY 2001), pp. 191-216.
BRITTLE-DUCTILE RELAXATION KINETICS OF STRAINED ALGAN/GAN HETEROSTRUCTURES, S. J. Hearne, J. Han, S. R. Lee, J. A. Floro, and D. M. Follstaedt, Appl. Phys. Lett. 76, 1534 (2000).
NOVEL SIGE ISLAND COARSENING KINETICS: OSTWALD RIPENING AND ELASTIC INTERACTIONS, J. A. Floro, M. B. Sinclair, E. Chason, L. B. Freund, R. D. Twesten, R. Q. Hwang, and G. A. Lucadamo, Phys. Rev. Lett. 84, 701 (2000).
SiGe ISLAND SHAPE TRANSITIONS INDUCED BY ELASTIC REPULSION, J. A. Floro, G. A. Lucadamo, E. Chason, L. B. Freund, M. Sinclair, R. D. Twesten, and R. Q. Hwang, Phys. Rev. Lett. 80, 4717 (1998).
SiGe COHERENT ISLANDING AND STRESS RELAXATION IN THE HIGH MOBILITY REGIME, J. A. Floro, E. Chason, R. D. Twesten, R. Q. Hwang, and L. B. Freund, Phys. Rev. Lett. 79, 3946 (1997)