Theory of the scanning tunneling microscope
01 Jan 1985-Vol. 6, pp 59-67
TL;DR: A theory for tunneling between a real surface and a model probe tip, applicable to the recently developed "scanning tunneling microscope" is presented and it is concluded that for the AuOlO measurements the experimental "image" is relatively insensitive to the positions of atoms beyond the first atomic layer.
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.
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University of the Basque Country1, University of Barcelona2, Technical University of Denmark3, Malmö University4, University of Copenhagen5, SINTEF6, Aarhus University7, Brown University8, University of Wisconsin-Madison9, University of Warwick10, Carnegie Mellon University11, Purdue University12, Karlsruhe Institute of Technology13, ETH Zurich14, University of Freiburg15
TL;DR: The atomic simulation environment (ASE) provides modules for performing many standard simulation tasks such as structure optimization, molecular dynamics, handling of constraints and performing nudged elastic band calculations.
Abstract: The Atomic Simulation Environment (ASE) is a software package written in the Python programming language with the aim of setting up, steering, and analyzing atomistic simula- tions. In ASE, tasks are fully scripted in Python. The powerful syntax of Python combined with the NumPy array library make it possible to perform very complex simulation tasks. For example, a sequence of calculations may be performed with the use of a simple "for-loop" construction. Calculations of energy, forces, stresses and other quantities are performed through interfaces to many external electronic structure codes or force fields using a uniform interface. On top of this calculator interface, ASE provides modules for performing many standard simulation tasks such as structure optimization, molecular dynamics, handling of constraints and performing nudged elastic band calculations.
2,282 citations
Book•
20 May 1993
TL;DR: In this paper, the authors present an overview of the imaging mechanism for tunneling, including tip-sample interactions and tip treatment, and a detailed description of the tunneling matrix elements.
Abstract: 1: Overview. Part I: Imaging Mechanism. 2: Atom-scale tunneling. 3: Tunneling matrix elements. 4: Wavefunctions at surfaces. 5: Imaging crystalline surfacces. 6: Imaging atomic states. 7: Atomic forces and tunneling. 8: Tip-sample interactions. Part II: Instrumentation. 9: Piezoelectric scanner. 10: Vibration isolation. 11: Electronics and control. 12: Coarse positioner and STM design. 13: Tip treatment. 14: Scanning tunneling spectroscopy. 15: Atomic force microscopy. 16: Illustrative examples. Appendices. References. Index
1,413 citations
Cites methods from "Theory of the scanning tunneling mi..."
...According to the Tersoff-Hamann model of STM imaging [16, 17] (see Chapter 6), a topographic STM image is the contour of equal Fermi-level local density of states of the sample, measured at the center-of-curvature of the tip r0, ρ(EF , r0)....
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TL;DR: This Review covers the major advances with the most general applicability and emphasizes new insights into the development of efficient platform methodologies for building reliable molecular electronic devices with desired functionalities through the combination of programmed bottom-up self-assembly and sophisticated top-down device fabrication.
Abstract: Creating functional electrical circuits using individual or ensemble molecules, often termed as “molecular-scale electronics”, not only meets the increasing technical demands of the miniaturization of traditional Si-based electronic devices, but also provides an ideal window of exploring the intrinsic properties of materials at the molecular level. This Review covers the major advances with the most general applicability and emphasizes new insights into the development of efficient platform methodologies for building reliable molecular electronic devices with desired functionalities through the combination of programmed bottom-up self-assembly and sophisticated top-down device fabrication. First, we summarize a number of different approaches of forming molecular-scale junctions and discuss various experimental techniques for examining these nanoscale circuits in details. We then give a full introduction of characterization techniques and theoretical simulations for molecular electronics. Third, we highlig...
949 citations
TL;DR: The patterning of graphene nanoribbons and bent junctions are patterned with nanometre-precision, well-defined widths and predetermined crystallographic orientations, allowing us to fully engineer their electronic structure using scanning tunnelling microscope lithography.
Abstract: The practical realization of nanoscale electronics faces two major challenges: the precise engineering of the building blocks and their assembly into functional circuits. In spite of the exceptional electronic properties of carbon nanotubes, only basic demonstration devices have been realized that require time-consuming processes. This is mainly due to a lack of selective growth and reliable assembly processes for nanotubes. However, graphene offers an attractive alternative. Here we report the patterning of graphene nanoribbons and bent junctions with nanometre-precision, well-defined widths and predetermined crystallographic orientations, allowing us to fully engineer their electronic structure using scanning tunnelling microscope lithography. The atomic structure and electronic properties of the ribbons have been investigated by scanning tunnelling microscopy and tunnelling spectroscopy measurements. Opening of confinement gaps up to 0.5 eV, enabling room-temperature operation of graphene nanoribbon-based devices, is reported. This method avoids the difficulties of assembling nanoscale components and may prove useful in the realization of complete integrated circuits, operating as room-temperature ballistic electronic devices.
900 citations
Cites background from "Theory of the scanning tunneling mi..."
...At low bias voltages the STM measurements map the (square modulus of the) electronic wavefunction near the Fermi leve...
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644 citations
References
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IBM1
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
TL;DR: In this article, a theory for vacuum tunneling between a real solid surface and a model probe with a locally spherical tip is presented, applicable to the recently developed "scanning tunneling microscope."
Abstract: A theory is presented for vacuum tunneling between a real solid surface and a model probe with a locally spherical tip, applicable to the recently developed "scanning tunneling microscope." Calculations for 2\ifmmode\times\else\texttimes\fi{}1 and 3\ifmmode\times\else\texttimes\fi{}1 reconstructions of Au(110) are in excellent agreement with recent experimental results, if an effective radius of curvature of 9 \AA{} is assumed for the tip.
2,091 citations
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
1,562 citations
IBM1
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.
1,550 citations