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Electron and Optical Physics Coherent Matter Waves and Quantum Information Photodiode Detectors for Radiometry Synchrotron Ultraviolet Radiation Facility Nanofabrication With Atom Optics Theory of Nanostructured Systems |
Division Contact: Charles W. Clark Coherent Matter Waves and Quantum Information We conduct theoretical and computational research directed at modeling the dynamics of quantum-degenerate gases on a first-principles basis to provide the tools needed for design of matter-wave circuits and quantum information processing devices. Codes have been developed to simulate fully anisotropic, three-dimensional Bose-Einstein and Fermi-Dirac degenerate gases, and to determine their responses to thermal, mechanical and optical excitation. Topics under investigation include nanokelvin thermometry, vortex and soliton generation, and deterministic loading of optical lattices with ultracold atoms. Contact: Charles
Clark Photodiode Detectors for Radiometry We develop, calibrate, and distribute highly stable photodiode detectors with uniform spatial sensitivity as transfer standard detectors for radiometry in the wavelength region of 5 nanometers to 254 nanometers. Detectors presently available at NIST include Al2O3 photocathode windowless photodiodes for the region 5 nanometers to 122 nanometers; CsTe photocathode windowed (evacuated) photodiodes for the region 116 nanometers to 254 nanometers; and silicon photodiodes, developed in collaboration with industry, for the region 5 nanometers to 254 nanometers. Some other types of detectors can be calibrated by special arrangement, such as dosimeters for extreme ultraviolet lithography (EUVL) at 13 nanometers. Broadband photometers also have been developed in collaboration with outside users and calibrated in this spectral region, e.g., combinations of silicon photodiodes with thin-film filters for plasma diagnostics and vacuum ultraviolet solar radiometry. Contact: Rob Vest The emerging field of high-reflectance, normal-incidence soft X-ray or extreme ultraviolet (EUV) optics has a wide range of applications. The ability to produce high-quality images at wavelengths below 40 nanometers has allowed construction of EUV solar telescopes with unprecedented resolution, EUV microscopes able to study living biological samples with submicrometer resolution, and EUV lithography systems that are proposed as tools for the next generation of integrated circuits. NIST has an EUV multilayer characterization facility at the Synchrotron Ultraviolet Radiation Facility. The current facility was designed to measure the reflectance or transmittance of EUV optics such as mirrors, filters, and gratings as a function of wavelength, angle of incidence, and position on the optic. NIST is in the process of commissioning a new facility that will extend measurement capabilities to larger and more curved optics and shorter wavelength, such as those. A thin-film deposition chamber has been added to the reflectometry facility that allows measurements of films as they are being deposited. From these measurements, the optical constants of important multilayer materials can be determined free from influence of surface contaminants. Contact: Charles Tarrio The analysis of buried structures with submicron resolution is often of high technological or scientific interest. This interest has given rise to major efforts at synchrotron facilities worldwide in X-ray microscopy and tomography to investigate biological objects and structured devices with submicron-scaled features. NIST has a program in collaboration with the microelectronics industry to develop nanotomography of integrated circuits with special emphasis on the study of buried interconnects. Using X-ray microscope facilities at third-generation synchrotron X-ray sources, we have achieved three-dimensional reconstructions of two-level microcircuits with 140-nanometer resolution. Work is presently under way to improve the resolution to better than 100 nanometers on circuits with six or more layers. Contact: Zachary Levine Synchrotron Ultraviolet Radiation Facility (SURF III) SURF III is an electron storage ring facility, operating at 380 megaelectronvolts electron beam energy, with injection currents of 400 milliamperes, which generates a continuum of radiation from the infrared to the extreme ultraviolet (EUV). SURF provides the national primary standard for source-based radiometry in the UV and EUV spectral regions and also serves as a source for detector-based radiometry, calibration services, and EUV optical metrology. SURF beamlines can be made available to external users needing a bright source of UV or EUV radiation. Contact: Charles
Clark The magnetic nanostructure of various materials, such as thin films, multilayers, and particulates, plays a key role in their macroscopic magnetic properties and, therefore, determines their eventual usefulness in technological applications, such as recording media, magnetic sensors, and spintronic devices. We are using scanning electron microscopy with polarization analysis (SEMPA), along with magneto-optic microscopy and magnetic force microscopy, to investigate the magnetic nanostructure of such materials and devices. Our primary technique is SEMPA, since it can directly image magnetic structure, along with physical and chemical structure, with 10-nanometer resolution. In addition, SEMPA's high surface sensitivity makes it an especially powerful technique for investigating the magnetization of surfaces, thin films, and multilayers. SEMPA measurements have been used to resolve the origins of oscillatory exchange coupling in magnetic multilayers and have been used to quantify the relationships between interlayer magnetic domain correlations and magnetoresistance in magnetic multilayer sensor materials. Contact: John
Unguris Nanofabrication With Atom Optics We are studying the physics of laser focusing of atom beams to find ways to develop a fabrication tool that could lead to more compact microcircuits, higher density magnetic recording media, better sensors, and novel materials. Laser beams form lenses that focus neutral atoms into tiny regions as they deposit, building nanostructures on a surface. The chromium atoms used in this process emerge from an effusive, high-temperature oven, are collimated by laser cooling, and pass through a laser standing wave that acts as an array of lenses, focusing the atoms into an array of lines. The nanofabrication of a two-dimensional array of chromium dots also can be achieved by using two orthogonal standing waves. The very regular arrays of chromium lines and dots with spacing tied to optical wavelength promise to provide useful standards. Atom optical methods potentially can be extended to a much broader range of materials. Metastable rare gas atoms can be manipulated with lasers and contain internal energy that has been used to expose a resist. A pattern of light can be used to de-excite the metastables; in this way light can be used as a mask for matter, instead of matter being used as a mask for light as in optical lithography. Contact: Jabez
McClelland Theory of Nanostructured Systems We use many theoretical techniques to study a wide range of problems related to the nanoscale interactions of electrons in solids, including electronic structure calculations, transport in magnetic multilayers (giant magnetoresistance), exchange coupling in magnetic multilayers, surface growth, spin-dependent reflection from interfaces, magnetic hysteresis in ultrathin films, light emission produced by scanning tunneling microscopy of a magnetic surface, electron energy loss in magnetic and non-magnetic solids, high-temperature superconductivity, and various microscopic tunneling phenomena. Our results are used to help interpret and guide experiments and provide a theoretical understanding crucial to the development and application of new measurement techniques. Contacts: David Penn or Mark Stiles Tunneling Microscopy of Nanoscale Magnetic Materials Scanning tunneling microscopy (STM) is a highly sensitive probe of surfaces, which utilizes the quantum mechanical principle of tunneling to probe surface topography on a nanometer scale. The STM also is inherently sensitive to surface electronic properties that can be exploited to detect the surface electron density of states. We have used an ultrahigh vacuum STM with extensive facilities for tip and sample preparation and characterization to investigate four main areas relating to nanometer-scale magnetic science: epitaxial growth, correlation of microstructure and magnetism, electron spin-dependent contrast measurements in STM, and the electronic properties of nanostructures. Our experimental efforts employ custom-designed instrumentation with which we strive to push the frontiers of visualization of the nanometer-scale world. Contact: Daniel
T. Pierce We have constructed a new laboratory to fabricate magnetic and electronic nanostructures and measure their physical properties on the atomic scale. We focus our research on quantum and spin electronics as part of the emerging nanotechnology revolution. The Nanoscale Physics Laboratory's key component is a scanning tunneling microscope, designed and constructed at NIST to have a very high spatial and energy resolution: it can measure displacements as small as 10-12 meter and resolve electronic energy levels separated by 600 microvolts. Operating in cryogenic, high magnetic field, and ultrahigh vacuum environments, the microscope measures electronic and magnetic properties of nanostructures on an atom-by-atom basis. Facilities for fabrication of nanostructures include molecular beam epitaxy of III-V semiconductors, metals, superconductors, as well as bottom up nanofabrication using autonomous atom assembly. Contact: Joseph
A. Stroscio or Robert
J. Celotta
Date
created:
October 1, 2001 |