共查询到20条相似文献，搜索用时 46 毫秒
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Edelson I 《Science (New York, N.Y.)》1968,160(3829):797-798
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Flowers J 《Science (New York, N.Y.)》2004,306(5700):1324-1330
Over the past half-century, there has been a shift away from standards based on particular artifacts toward those based on physical effects, the most stable being based on quantum properties of systems. This change was proposed at the end of the 19th century but is still not complete at the start of the 21st. We discuss how this vision has been implemented through recent advances in science and metrology and how these may soon lead to an SI system finally free from artifact standards, with a consistency based on fundamental constants. 相似文献
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Weber B Mahapatra S Ryu H Lee S Fuhrer A Reusch TC Thompson DL Lee WC Klimeck G Hollenberg LC Simmons MY 《Science (New York, N.Y.)》2012,335(6064):64-67
As silicon electronics approaches the atomic scale, interconnects and circuitry become comparable in size to the active device components. Maintaining low electrical resistivity at this scale is challenging because of the presence of con?ning surfaces and interfaces. We report on the fabrication of wires in silicon--only one atom tall and four atoms wide--with exceptionally low resistivity (~0.3 milliohm-centimeters) and the current-carrying capabilities of copper. By embedding phosphorus atoms within a silicon crystal with an average spacing of less than 1 nanometer, we achieved a diameter-independent resistivity, which demonstrates ohmic scaling to the atomic limit. Atomistic tight-binding calculations con?rm the metallicity of these atomic-scale wires, which pave the way for single-atom device architectures for both classical and quantum information processing. 相似文献
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Metz WD 《Science (New York, N.Y.)》1972,176(4033):394-395
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Walsh J 《Science (New York, N.Y.)》1976,194(4267):812-814
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Stebbings RF 《Science (New York, N.Y.)》1976,193(4253):537-542
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Laser-focused atomic deposition 总被引：1，自引：0，他引：1
The ability to fabricate nanometer-sized structures that are stable in air has the potential to contribute significantly to the advancement of new nanotechnologies and our understanding of nanoscale systems. Laser light can be used to control the motion of atoms on a nanoscopic scale. Chromium atoms were focused by a standing-wave laser field as they deposited onto a silicon substrate. The resulting nanostructure consisted of a series of narrow lines covering 0.4 millimeter by 1 millimeter. Atomic force microscopy measurements showed a line width of 65 +/- 6 nanometers, a spacing of 212.78 nanometers, and a height of 34 +/-+ 10 nanometers. The observed line widths and shapes are compared with the predictions of a semiclassical atom optical model. 相似文献
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Imaging crystals, polymers, and processes in water with the atomic force microscope 总被引：45，自引：0，他引：45
B Drake C B Prater A L Weisenhorn S A Gould T R Albrecht C F Quate D S Cannell H G Hansma P K Hansma 《Science (New York, N.Y.)》1989,243(4898):1586-1589
The atomic force microscope (AFM) can be used to image the surface of both conductors and nonconductors even if they are covered with water or aqueous solutions. An AFM was used that combines microfabricated cantilevers with a previously described optical lever system to monitor deflection. Images of mica demonstrate that atomic resolution is possible on rigid materials, thus opening the possibility of atomic-scale corrosion experiments on nonconductors. Images of polyalanine, an amino acid polymer, show the potential of the AFM for revealing the structure of molecules important in biology and medicine. Finally, a series of ten images of the polymerization of fibrin, the basic component of blood clots, illustrate the potential of the AFM for revealing subtle details of biological processes as they occur in real time. 相似文献
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The (1014) cleavage plane of calcite has been investigated by atomic force microscopy in water at room temperature. True lateral atomic-scale resolution was achieved; the atomic-scale periodicities as well as the expected relative positions of the atoms within each unit cell were obtained. Along monoatomic step lines, atomic-scale kinks, representing point-like defects, were resolved. Attractive forces on the order of 10(-11) newton acting between single atomic sites on the sample and the front atoms of the tip were directly measured and provided the highest, most reliable resolution on a flat, well-ordered surface. 相似文献
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Negative differential resistance (NDR) is the essential property that allows fast switching in certain types of electronic devices. With scanning tunneling microscopy (STM) and scanning tunneling spectroscopy, it is shown that the current-voltage characteristics of a diode configuration consisting of an STM tip over specific sites of a boron-exposed silicon(111) surface exhibit NDR. These NDR-active sites are of atomic dimensions ( approximately 1 nanometer). NDR in this case is the result of tunneling through localized, atomic-like states. Thus, desirable device characteristics can be obtained even on the atomic scale. 相似文献
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Scanning tunneling microscopy and atomic force microscopy: application to biology and technology 总被引：18，自引：0，他引：18
The scanning tunneling microscope (STM) and the atomic force microscope (AFM) are scanning probe microscopes capable of resolving surface detail down to the atomic level. The potential of these microscopes for revealing subtle details of structure is illustrated by atomic resolution images including graphite, an organic conductor, an insulating layered compound, and individual adsorbed oxygen atoms on a semiconductor. Application of the STM for imaging biological materials directly has been hampered by the poor electron conductivity of most biological samples. The use of thin conductive metal coatings and replicas has made it possible to image some biological samples, as indicated by recently obtained images of a recA-DNA complex, a phospholipid bilayer, and an enzyme crystal. The potential of the AFM, which does not require a conductive sample, is shown with molecular resolution images of a nonconducting organic monolayer and an amino acid crystal that reveals individual methyl groups on the ends of the amino acids. Applications of these new microscopes to technology are demonstrated with images of an optical disk stamper, a diffraction grating, a thin-film magnetic recording head, and a diamond cutting tool. The STM has even been used to improve the quality of diffraction gratings and magnetic recording heads. 相似文献
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