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Table of Contents
Introduction The condensed matter group studies the fundamental nature of classical and quantum solids and liquids, of complex materials, and of nanostructures over a wide range of experimental conditions. The structure and dynamics of the phases and phase transitions of bulk matter and its surfaces are examined by means of diverse microscopic and thermodynamic techniques, including x- ray, electron, and neutron scattering, optical, electron and gamma ray spectrometry, scanning probe microscopy, flourescence microscopy, low temperature calorimetry, and electrical transport. The interplay between theory and experiment is particularly lively. Members of the condensed-matter group also frequently collaborate with researchers in other disciplines -- such as Chemistry, Earth & Space Sciences (previously Geophysics) , Atmospheric Sciences, Electrical Engineering, Applied Physics Laboratory, and Materials Science and Engineering -- and with groups at several other universities and laboratories in the US and other nations. Experimental condensed matter research at the UW can be loosely divided into three overlapping areas: fabrication and properties of nanostructures and surfaces, structural aspects of materials, and ice physics. Nanostructures: Surfaces, Interfaces and Lower-Dimensional Systems A reduction in dimensionality of a condensed matter system can cause profound changes in its properties. Very thin films and their interfaces with bulk solids and liquids display unusual phases and phase transitions -- some of which resemble theoretical models of two- dimensional matter and many of which have no analogues in ordinary bulk materials. Key questions remain unanswered about the synthesis and properties of heterostructures whose dimensions can be measured by the number of atoms. Work at the University of Washington involves synthesis of these quantum nanostructures, analysis of their structures, thermodynamics, and mechanical properties on the atomic scale, and measurement of the optical properties, phase behavior, electronic states, and transport in these structures. The Low Temperature Laboratory (Vilches) probes the phases and phase transitions of quasi two- and one-dimensional films and lines of classical and quantum substances. Current interest is in the thermal and structural properties of films of hydrogen, deuterium, the helium stable isotopes and their mixtures deposited on well-characterized crystalline substrates (exfoliated graphite, MgO), and in the properties of lines of atoms and/or molecules (helium, hydrogen, argon, nitrogen and oxygen) formed by low temperature deposition in the interstitial channels or carbon nanotube bundles. The principle techniques are calorimetry and adsorption isotherms, done in Seattle, and elastic and quasi-elastic neutron scattering done in Europe in collaboration with French, German, and American scientists. The Nanodevice Physics Laboratory contains facilities for fabricating and studying electronic and electrooptic devices made from individual chemically derived nanostructures, including hollow carbon nanotubes, solid nanowires of semiconductors and metals, and elongated polymer structures. The focus is on employing these devices to search for new quantum phenomena specific to nanostructures, often requiring the use of millikelvin temperatures and high magnetic fields. The research program of the Surface Properties Laboratory(Fain) is currently concentrating on the use of scanning probe microscopy to investigate surface forces and interactions. Of particular interest are the nanoscale mechanical properties of the ice surface and its interface with solid materials, forces involved in intermittent-contact force microscopy, and the use of carbon nanotubes attached to force microscopy probes for high resolution imaging. Research in the Heteroepitaxial Growth Laboratory (Olmstead) focuses on understanding both the mechanisms of thin film growth and the unique properties of the resultant low-dimensional structures. Experiments probe the development of electronic, optical and atomic structure during growth of crystalline films on dissimilar substrates, using combined facilities for molecular beam epitaxy and materials characterization. Of particular interest are nanostructures combining silicon with another material of very different atomic and electronic structure,for example an ionic insulator or a van der Waals semiconductor. The X-Ray Scattering Laboratory (Sorensen) focuses on structural and dynamical studies of surfaces under electrochemical conditions, crystalline superlattices, and freely suspended liquid crystal films. Research performed at the UW uses a high intensity rotating anode x-ray generator and two high precision computer- controlled goniometers in combination with scanning probe microscopy. The research also employs very intense synchrotron x- ray sources at national laboratories to study the same systems. Several adjunct faculty members also study nanostructures and surfaces. Research projects in chemistry, biophysics, bioengineering and materials science involving physics graduate students include: growth morphologies of metal films of interest in microelectronics or as model catalysts, using adsorption microcalorimetry, scanning probe microscopy and various ion and electron spectroscopies (Campbell); formation of domains in vesicle models of cell membranes and thin surfactant films, including spinodal decomposition (Keller); etching of semiconductor surfaces, using molecular beam scattering and scanning probe microscopy (Engel); growth and properties of semiconductor nanostructures, using chemical vapor deposition, molecular beam epitaxy, and a number of optical, electronic, x-ray, and microscopic characterization tools (Pearsall); fabrication processes for nanoscale integrated circuits, characterization of carrier and impurity distributions in semiconductors, nanostructure fabrication via self-limiting stress dependent film growth (Dunham). Structural Aspects of Materials The structural arrangements of atoms and how these arrangements change in phase transitions or during growth are among the most basic information for understanding the properties of materials. The techniques of x- ray absorption fine structure (XAFS), x-ray holography, photoemission, and photoelectron diffraction can give detailed information on short range order and the structural and chemical environments of specific atomic species. X-ray and electron diffraction yield complementary information on long range order. By combining these structural studies with optical and electronic spectroscopies, the interplay between structure and properties is investigated. In the XAFS Laboratory (Stern), x-ray absorption and scattering techniques are being applied to study the nucleation of melting by impurities, the structural changes in ferroelectric and anti ferroelectric displacive transitions, the local structure in disordered materials, and the local structural variation in high temperature superconductors. Anomalous diffuse x- ray scattering and Raman scattering (Seidler) are used as complementary probes in measurements of ion-pairing in chemical solutions where the solvent is beyond the liquid-vapor critical point; these studies have immediate relevance for the use of supercritical chemistry in toxic waste remediation. In the X-Ray Scattering Laboratory (Sorensen), the new technique of x-ray holography is being developed. This technique exploits x-ray fluorescence and bremsstrahlung radiation to obtain atomic scale information about atoms embedded in solids. In the Microstructural Kinetics Laboratory (Seidler), research focuses on the equilibrium and non-equilibrium statistical mechanics of disordered solids and complex materials (gels, granular systems, colloids, etc.). Fluctuations in microstructure, including surface roughness, defect configurations and colloid distribution, may be strongly correlated with fluctuations in thermodynamic, electronic and optical properties. These are studied with a combination of electronic transport, light scattering and dynamical x-ray scattering techniques. Ice Physics An interdisciplinary group of faculty members and students is conducting wide ranging research on the fundamental and applied physics of snow and ice and their environmental manifestations (Dash, Fain, Baker, Seidler, Wettlaufer). Ice has enormous environmental importance, through the influence of snow and ice cover on the global climate, the scavenging of atmospheric pollutants by snow, stratospheric ice clouds and their role in ozone destruction, frost heave on roads and engineered structures, and freeze damage to agricultural products and soils. These phenomena depend in large degree on the molecular physics of ice and its phase transformations. Several current research projects are addressing the physical basis of ice phenomena. They include studies of nucleation and crystallization dynamics, surface melting, adhesion and friction on a nanometer scale, the microscopic mechanism of electrical charging of thunderstorms, freezing in saline and porous media, and the application of ground freezing for the management of hazardous wastes. Experimental techniques include opticalpolarimetry, interference microscopy, ellipsometry, thermometry, calorimetry, atomic force microscopy, dynamic light scattering, and novel crystal growth and porous media cells. Facilities In addition to facilities in individual laboratories, the Physics Department is also actively involved in using national and international Facilities for x-ray, ultraviolet and neutron studies. In particular, a consortium, with the UW as lead institution and under leadership from UW condensed matter faculty, is constructing and using the PNC-CAT beamline at the Advanced Photon Source, the most brilliant source of x-rays in the world. In addition, members of the group are closely associated with beamlines at the Advanced Light Source, which provides high- brilliance in the vacuum ultraviolet photon range. These facilities provide an opportunity to investigate fundamental properties of matter, as well as environmental science and molecular biophysics, with spatial resolutions in the sub-micron range. The University of Washington has recently begun a campus-wide initiative in nanotechnology, which involves several members and adjunct members of the physics faculty. The Nanotechnology User Facility will provide central equipment and technical support in the growing field of nanotechnology, especially for high resolution microscopies and spectroscopies. There are also excellent electron microscopy facilities, operated in the Department of Materials Science and Engineering and the Nanotechnology User Facility, to which physics faculty and students have access. Laboratories in the Experimental Condensed Matter Group
New Facilities Development Thanks to departmental, University, and Federal support the condensed matter group is in the process of constructing and inaugurating several new experimental facilities.
Graduate Assistantships in Experimental Condensed Matter Physics Upon joining a research lab, graduate students are generally supported as research assistants (RA's) on the research grants associated with lab's director. Most students will be supported as RA's at least 3 of 4 quarters per year, with teaching assistant positions covering graduate stipends for the fourth quarter; in several labs, students are supported as RA's for all four academic quarters for the remainder of their graduate career after choosing a dissertation supervisor. There are presently approximately 25 physics graduate students with RA positions in the experimental condensed matter group. Due to growth of the number of faculty in the group, increases in grant support, continued development at the PNC-CAT synchrotron x-ray beamline, the creation of the UW Center for Nanotechnology, and a large number of anticipated Ph.D. graduations in the next two academic years, it is expected that at least 13 and possibly as many as 18 new graduate RA positions will be available in the group in the next two calendar years 1998-2000. Positions are anticipated in each of the labs of the condensed matter group. For more information on graduate opportunities in the experimental condensed matter physics group, or to schedule a campus visit, contact Prof. Sam Fain, or any other member of the experimental condensed matter faculty working on research of particular interest to you. Index of Research Topics in Experimental Condensed Matter Physics and Biophysics
Faculty in Experimental Condensed Matter Physics
Recent Ph.D. Dissertations in Experimental Condensed Matter Physics
Funding Research in the UW Experimental Condensed Matter Physics Group is funded by several sources, including: the U.S. National Science Foundation, the U.S. Department of Energy, The Leonard X. Bosack and Bette M. Kruger Charitable Foundation, the Research Corporation, UW Center for Nanotechnology, the UW/PNNL JIN, and the Alfred P. Sloan Foundation. UW Physics Department Home Page
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