| Major Professsional Experience |
01/08-present Henry Burlage Jr. Professor of Engineering and Department Head,
Materials
Science and Engineering, Rensselaer Polytechnic Institute
01/08-present Visiting Professor, University of Virginia
08/02-12/07 Director, University of Virginia Institute for Nanoscale and Quantum Science
08/02-12/07 Charles Henderson Professor of Engineering, University of Virginia
09/00-present Director, UVa Materials Research Science and Engineering Center
06/99-present Professor, Department of Materials Science and Engineering, UVA
10/97-08/02 Heinz and Doris Wilsdorf Distinguished Research Chair
10/97-present Courtesy appointment in Department of Electrical Engineering, UVA
11/94-06/99 Associate Professor, Department of Materials Science and Engineering, UVA
12/92-3/93 Visiting Associate Professor, University of Tokyo, Japan (NEC Chair
1987-1994 Member of Technical Staff, AT&T Bell Laboratories
1985-1987 Member of Technical Staff, Hewlett Packard Laboratories
1983-1985: Postdoctoral Member of Technical Staff, AT&T Bell Laboratories
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The over-arching themes of our research efforts are the fields of nanoscience and nanotechnology.
Within these broad themes, my group’s research activities focus upon structure-property relationships in electronic materials, fundamental mechanisms of thin film growth, self-assembly of nanoscaled structures, degradation modes in electronic and optoelectronic devices, the properties of dislocations in semiconductors, nanoscale fabrication techniques, nanoscale tomographic reconstruction techniques, and the theory and application of electron and ion beams.
A primary emphasis is upon developing programs centered upon the applications of focused ion beam (FIB) and transmission electron microscope (TEM) techniques to the nanostructural study of electronic materials and devices, and to nanofabrication of electronic materials. My group has developed techniques for direct correlation of microstructure and chemistry with materials and device degradation, thereby providing new interfaces between materials science and electrical engineering. Another emphasis is upon development of techniques to directly image dopant distributions with nm-scale resolution in the TEM. These combined FIB-TEM programs have been funded by IBM (high speed GeSi/Si devices and circuits), Sandia National Laboratories (surface emitting visible and infra-red lasers), the Semiconductor Industry Association (nanoscale stress mapping and tomographic reconstructions in next generation Si device architectures), and the National Science Foundation (quantum device structures, and imaging of dislocations at heteroepitaxial interfaces).
We are also developing FIB-based techniques for fabrication of electronic devices which are compatible with operation directly inside the transmission electron microscope. This would allow us to directly observe those microstructural processes which initiate device degradation mechanisms. Experimental facilities are being developed which allow for simulatneous application of thermal, mechanical, electrical and optical stresses to such structures, in-situ in the TEM.
Another major thrust in FIB-based research is the development of nanoscale printing technologies based upon direct contacting of FIB-fabricated printheads with thin film “print media”. Such a technology has potential for extending lithography far beyond current optically-based systems to new materials, dimensions and geometries. We have been awarded a $2.7 million program by DARPA to explore this potential technology. We have been able to demonstrate pattern FIB patterning of printheads with feature sizes of 100 nm over fields up to 1 mm2, containing hundreds of thousands of features. Pattern transfers at the deep sub-micron scale (best result to date: 90 nm) have been achieved using self assembling organic monolayers, mechanical imprinting into resist, and seeded anodic etching. In the past year, we have also received an additional grant from ONR to explore applications of these approaches to nano-magnetic devices.
We are also developing new FIB-based analytical techniques including ultra-high resolution secondary ion mass spectroscopy, tomographic image reconstruction techniques and rapid nanostructural prototyping. These tools are central to large programs (funded by NSF and DARPA) together with collaborators from MIT, Notre Dame and other institutions to understand three dimensional materials structure and chemistry at the nanoscale.
Another primary focus of our group is upon improved understanding of the fundamental mechanisms of strained layer epitaxy, particularly upon the role of surface morphology and dislocations in strain relief. A substantial program in this area is being funded by the National Science Foundation. We are developing new experimental techniques to significantly enhance our understanding of dislocations in epitaxial structures and in semiconductors in general. Experimental measurements are being combined into a comprehensive predictive program for dislocation relaxation during growth, annealing, processing and operation of strained layer heterostructure devices.
Other research efforts are focusing upon development of electron microscopy techniques. One goal is to develop higher time-resolution transmission electron microscopy techniques, via collection of images by charge-coupled devices at rates much higher than conventional TV rates. We hope to be able to obtain image acquisition times in the millisecond regime, enabling us to study a wide range of rapid solid state phenomena in real time in the TEM. We have recently developed a new technique for rapid evaluation of polycrystalline thin film texture and grain size using annular objective apertures fabricated in the focused ion beam. We have also been collaborating with colleagues at IBM studying thin film (GeSi/Si and Ti/SiO2) growth processes in-situ in a specially modified TEM, and novel high spatial- and temporal- resolution experiments using a cell designed for nanoscale studies of liquid-solid interfaces in the TEM
A major initiative is the funding of a large NSF Center, the “Center for Nanoscopic Materials Design”, of which I am the Director, for studying controlled nucleation and attachment of nano-scaled structures onto semiconductor surfaces. This program incorporates extensive modeling and characterization studies to understand the fundamental mechanisms of atom-by-atom growth upon topographically or chemically patterned semiconductor surfaces. Applications being explored for such structures are “quantum cellular automata” (which are nanoscaled single electron transfer electronic device architectures offering the promise of far higher computational speeds and complexities than for conventional microelectronic circuits, in collaboration with Greg Snider at Notre Dame University ), controlled adhesion of proteins for biomedical applications (with Brian Hemlke, BME), and templating of ordered gel structures with applications as viral filters and for biological threat detection (with Pam Norris, MAE)
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Fellow, American Physical Society
Elected, Member of European Academy of Sciences.
Chair, Gordon Research Conference on Thin Films, 1993
Elected President of Materials Research Society, 1997
Chair of Committee of Visitors for NSF Division of Materials Research, 1999
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“Lateral control of self-assembled island nucleation by focused-ion-beam-micropatterning”, M. Kammler, R. Hull, M.C. Reuter, and F.M. Ross, Appl. Phys. Lett. 82, 1093 (2003).
“Control of surface morphology through variation of growth rate in SiGe/Si(100) epitaxial films: Nucleation of quantum fortresses"; J. L. Gray, R. Hull and J.A. Floro, Appl. Phys. Lett. 81, 2445-7 (2002)
“Precision Placement of Heteroepitaxial Semiconductor Quantum Dots”, R. Hull, J.L. Gray, M. Kammler, S. Atha, P. Kumar, T. Vandervelde, J.C. Bean, J.A. Floro, and F.M. Ross, Mater. Sci. Eng. B101, 1-8 (2003)
“Misfit Strain Accommodation in SiGe Heterostructures”, R. Hull, in “Germanium Silicon: Physics and Materials” R. Hull and J.C. Bean, eds., Semiconductor and Semimetals Series Vol. 56 (Academic Press, San Diego, CA, 1998), pp102-168
“Nanoscale Characterization of Stresses in Semiconductor Devices by Quantitative Electron Diffraction”, J. Demarest, R. Hull , K. Schonenberg, and K. Janssens, Appl. Phys. Lett. 77 412-4 (2000)
“Ultrarapid nanostructuring of poly(methylmethacrylate) films using Ga+ focused ion beams,”Y. Liu, D.M. Longo, and R. Hull , Appl. Phys. Lett. 82, 346-8 (2003)
"Reconstruction of Three-Dimensional Chemistry and Geometry using Focused Ion Beam Microscopy”, D.N. Dunn and R. Hull, Appl. Phys. Lett., 75, 3414-6 (1999)
“A new mechanism for dislocation blocking in strained layer epitaxial growth”, E. A. Stach, K.W. Schwarz, R. Hull, F. M. Ross, and R.M. Tromp, Phys. Rev. Lett. 84, 947-50 (2000)
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