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Journal ArticleDOI

7 × 7 Reconstruction on Si(111) Resolved in Real Space

10 Jan 1983-Physical Review Letters (American Physical Society)-Vol. 50, Iss: 2, pp 120-123
TL;DR: In this paper, a modified adatom model with 12 adatoms per unit cell and an inhomogeneously relaxed underlying top layer was used for Si(111) reconstruction.
Abstract: The 7× 7 reconstruction on Si(111) was observed in real space by scanning tunneling microscopy. The experiment strongly favors a modified adatom model with 12 adatoms per unit cell and an inhomogeneously relaxed underlying top layer.
Citations
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Journal ArticleDOI
TL;DR: The most relevant features of WSXM, a freeware scanning probe microscopy software based on MS-Windows, are described and some relevant procedures of the software are carried out.
Abstract: In this work we briefly describe the most relevant features of WSXM, a freeware scanning probe microscopy software based on MS-Windows. The article is structured in three different sections: The introduction is a perspective on the importance of software on scanning probe microscopy. The second section is devoted to describe the general structure of the application; in this section the capabilities of WSXM to read third party files are stressed. Finally, a detailed discussion of some relevant procedures of the software is carried out.

6,996 citations

Journal ArticleDOI
TL;DR: The atomic force microscope (AFM) is not only used to image the topography of solid surfaces at high resolution but also to measure force-versus-distance curves as discussed by the authors, which provide valuable information on local material properties such as elasticity, hardness, Hamaker constant, adhesion and surface charge densities.

3,281 citations

Journal ArticleDOI
Jerry Tersoff1, D. R. Hamann1
TL;DR: In this paper, a metal tip is scanned along the surface while ad justing its height to maintain constant vacuum tunneling current, and a contour map of the surface is generated.
Abstract: The recent development of the “scanning tunneling microscope” (STM) by Binnig et al. [8.1–5] has made possible the direct real-space imaging of surface topography. In this technique, a metal tip is scanned along the surface while ad justing its height to maintain constant vacuum tunneling current. The result is essentially a contour map of the surface. This contribution reviews the the ory [8.6–8] of STM, with illustrative examples. Because the microscopic structure of the tip is unknown, the tip wave functions are modeled as s-wave functions in the present approach [8.6, 7]. This approximation works best for small effective tip size. The tunneling current is found to be proportional to the surface local density of states (at the Fermi level), evaluated at the position of the tip. The effective resolution is roughly [2A(R+d)]1/2, where R is the effective tip radius and d is the gap distance. When applied to the 2x1 and 3x1 reconstructions of the Au(l10) surface, the theory gives excellent agreement with experiment [8.4] if a 9 A tip radius is assumed. For dealing with more complex or aperiodic surfaces, a crude but convenient calculational technique based on atom charge superposition is introduced; it reproduces the Au(l10) results reasonably well. This method is used to test the structure-sensitivity of STM. The Au(l10) image is found to be rather insensitive to the position of atoms beyond the first atomic layer.

3,192 citations

Journal ArticleDOI
01 Jan 1996-Nature
TL;DR: In this article, it was shown that carbon nanotubes might constitute well defined tips for scanning probe microscopy, and they were attached to the silicon cantilevers of conventional atomic force microscopes.
Abstract: SINCE the invention of the scanning tunnelling microscope1, the value of establishing a physical connection between the macroscopic world and individual nanometre-scale objects has become increasingly evident, both for probing these objects2–4 and for direct manipulation5–7 and fabrication8–10 at the nanometre scale. While good progress has been made in controlling the position of the macroscopic probe of such devices to sub-angstrom accuracy, and in designing sensitive detection schemes, less has been done to improve the probe tip itself4. Ideally the tip should be as precisely defined as the object under investigation, and should maintain its integrity after repeated use not only in high vacuum but also in air and water. The best tips currently used for scanning probe microscopy do sometimes achieve sub-nanometre resolution, but they seldom survive a 'tip crash' with the surface, and it is rarely clear what the atomic configuration of the tip is during imaging. Here we show that carbon nanotubes11,12 might constitute well defined tips for scanning probe microscopy. We have attached individual nanotubes several micrometres in length to the silicon cantilevers of conventional atomic force microscopes. Because of their flexibility, the tips are resistant to damage from tip crashes, while their slenderness permits imaging of sharp recesses in surface topography. We have also been able to exploit the electrical conductivity of nanotubes by using them for scanning tunnelling microscopy.

2,179 citations

Journal Article

2,115 citations

References
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Journal ArticleDOI
TL;DR: In this paper, surface microscopy using vacuum tunneling has been demonstrated for the first time, and topographic pictures of surfaces on an atomic scale have been obtained for CaIrSn 4 and Au.
Abstract: Surface microscopy using vacuum tunneling is demonstrated for the first time. Topographic pictures of surfaces on an atomic scale have been obtained. Examples of resolved monoatomic steps and surface reconstructions are shown for (110) surfaces of CaIrSn 4 and Au.

4,290 citations

Journal ArticleDOI
TL;DR: In this article, the first successful tunneling experiment with an externally and reproducibly adjustable vacuum gap is reported, based on the exponential dependence of the tunneling resistance on the width of the gap.
Abstract: We report on the first successful tunneling experiment with an externally and reproducibly adjustable vacuum gap. The observation of vacuum tunneling is established by the exponential dependence of the tunneling resistance on the width of the gap. The experimental setup allows for simultaneous investigation and treatment of the tunnel electrode surfaces.

1,685 citations

Journal ArticleDOI
K. C. Pandey1
TL;DR: In this article, it was shown that buckling distortions can stabilize the surface of heteropolar semiconductors by returning the ions of the bulk to neutral atoms at the surface.
Abstract: Buckling distortions, widely thought to lower the total energy of semiconductor surfaces, are shown to actually raise the energy of Si(111)-2\ifmmode\times\else\texttimes\fi{}1. The $\ensuremath{\pi}$-bonded-chain reconstruction, in contrast, stabilizes the surface, even relative to recently proposed magnetic reconstructions. Calculations for GaAs(110) reveal that the large charge transfers associated with buckling can stabilize the surface of heteropolar semiconductors, by returning the ions of the bulk to neutral atoms at the surface. These conclusions are based on self-consistent pseudopotential calculations.

258 citations

Journal ArticleDOI
TL;DR: In this article, a tight-binding framework using the bond orbital approximation was proposed to simplify the total energy calculation. But the reconstruction of semiconductor surfaces was not considered, and it was shown that the 7 × 7 reconstruction is a pattern of add-atoms rather than (and topologically unrelated to) a patterns of vacancies.

201 citations

Journal ArticleDOI
TL;DR: In this article, the first few layers of Si(111)-Si(7)-(7\ifmmode\times\else\texttimes\fi{}7) have been determined with use of ion scattering.
Abstract: The parallel and perpendicular displacements of atoms in the first few layers of Si(111)-(7\ifmmode\times\else\texttimes\fi{}7) have been determined with use of ion scattering. It was directly observed that the major reconstruction of this surface involves \ensuremath{\sim}0.4 \AA{} displacements perpendicular to the surface.

90 citations