Event Scheduled for Feb 9, 2018
Event: MSE Seminar Speaker - Dr. Raymond Phaneuf
Time: 09:45 am
Details of Event:
Materials Science and Engineering Invites you to a seminar by
Dr. Ray Phaneuf
Professor and Interim Chair, Department of Materials Science and Engineering, University of Maryland
Friday, February 9, 2018
Institute of Materials Science Building, Room 20, at 9:45 a.m.
Refreshments will be served at 9:30 a.m.
“A Patterning Approach to Direct Self Assembly of Nanostructures at the Mesoscale”
Abstract: The next frontier beyond nanotechnology is arguably assembly at the meso-scale: that range of sizes from 10’s to 100’s of nm, with expectations of emergent properties at this scale. It has been argued that a hybrid approach combining top-down, and bottom-up aspects will be needed to accomplish assembly of nanostructures into meso-scale assemblies on a practical time scale. In this talk I present an example of just such an approach – using an artificially fabricated template along with molecular beam epitaxial growth in the presence of a kinetic barrier to direct the assembly on nm-scale growth mounds into mesoscale arrays. We show via both kinetic Monte Carlo (kMC) simulations and molecular beam epitaxial (MBE) growth experiments that patterning in the presence of an “Ehrlich_Schwoebel” diffusion barrier at step edges can be used to direct assembly of a series of “higher-order commensurate” mound-on-template structures. We find that in the initial stage of growth, the pattern directs the spontaneous formation of multilayer islands at 2-fold bridge sites between neighboring nanopits along  crystal orientation. However, as growth continues, the height of mounds at 2-fold bridge “self-limits”: the mounds cease to grow. Beyond this point an initially less favored 4-fold bridge site for mounds dominates and a different pattern of self assembled mounds begins. We find that the transient pattern amplification during growth proposed by Tadayyon-Eslami et al. is correlated with self-limiting behavior of mounds. We also propose that a minimum, ‘critical terrace size’ at the top of each mound is responsible for the observed self-limiting growth (SLG) behavior. *Work supported by NSF #DMR0705447
Bio: Ray Phaneuf is Professor and Interim Chair in the Department of Materials Sciences and Engineering at the University of Maryland. He earned his PhD in Physics at the University of Wisconsin-Madison in 1985. He then joined the Physics Department at the University of Maryland, where he used electron diffraction to study phase transformations on stepped Si(111) surfaces, resulting in the identification of a thermodynamically driven faceting associated with the formation of the (7x7) reconstruction. In 1989 he was a visiting scientist with Ernst Bauer’s group in Clausthal, Germany, using low energy electron microscopy (LEEM) to image this faceting in real time. In 2000 he joined the Materials Science and Engineering Department, and began studies of directed self-organization during growth, etching and sublimation on semiconductor, insulator and polymer surfaces, using lithographic patterning as a means of controlling the length scale. He was an original member of the UM NSF-MRSEC. In 2006 he was a visiting professor at the National Nanotechnology Laboratory, in Lecce, Italy. He is the founding director of the Interdisciplinary Minor in Nanoscience and Technology at the UM. He is the author of more than 100 journal articles, and has given over 40 invited talks on his work in the US, Europe and Japan. He was named the Laboratory for Physical Sciences Faculty Researcher of the year in 2002. He was named Interim Chair of MSE in 2015. He also holds affiliate professor positions in Physics and ECE. His current research is in the fields of directing self-assembly of nanostructures at the mesoscale, plasmonics, and the application of nanotechnology to the conservation of cultural heritage.
Target Audience: Not Available
Sponsored By: Materials Science and Engineering Department
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