Tunneling through adsorbate and thin films, induced conductivity, charge density waves

Maslova, N. S.; Moiseev, Yu. N.; Panov, V. I.; Savinov, S. Yu.; Vasil'ev, S.S.; Yaminskii, I. V.

doi:10.1002/pssa.2211310108

Cited by 8 publications

(2 citation statements)

References 5 publications

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“…This is generally caused by the following reasons. (i) For system sizes comparable to the atomic scale, the local density of states in the contact area can be strongly altered by the tunneling current (tip-sample interaction), resulting in the appearance of additional localized states near the Fermi level [2][3][4][5]. (ii) Individual localized states start to dominate the tunneling current, because the radii of the localized states become comparable to the area of the contact size [6].…”

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Influence of resonant tunneling on the imaging of atomic defects on InAs(110) surfaces by low-temperature scanning tunneling microscopy

Depuydt

Maslova

Panov

et al. 1998

Applied Physics A: Materials Science & Processing

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We have used a low-temperature scanning tunneling microscope (STM) to study the surface of heavily doped semiconductor InAs crystals. The crystals are cleaved in situ along the (110) plane. Apart from atomically flat areas, we also observe two major types of atomic-scale defects which can be identified as S dopant atoms and As vacancies, respectively. The strong bias voltage dependence of the STM image of the impurities can be explained in terms of resonant tunneling through localized states which are present near the impurity.With the advent of the scanning tunneling microscope (STM) and the decrease of system sizes down to the nanometer scale, experimental results can often no longer be interpreted in terms of the standard model for STM imaging [1], generally for the following reasons.-For system sizes comparable to the atomic scale, the local density of states in the contact area can be greatly altered by the tunneling current (tip-sample interaction), resulting in the appearance of additional localized states near the Fermi level [2-5]. -Individual localized states start to dominate the tunneling current, because the radii of the localized states become comparable to the area of the contact size [6]. -In the presence of localized states, the finite relaxation rate of the nonequilibrium electrons has to be taken into account, especially at low temperatures where the relaxation rate may become smaller than the tunneling rate [7]. In a recent publication we showed that the STM imaging and scanning tunneling spectroscopy of InAs(110) surfaces is strongly affected by tip-induced band bending, owing to charges which are present on localized states at the tip apex [8]. Here, we present a series of additional experimental results which demonstrate the role played by individual localized states related to atomic defects. In order to identify this role, we have imaged dopant atoms and vacancies appearing at the surface of the InAs compound semiconductor at a temperature of 4.2 K.

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“…To understand qualitatively the changes in the STM image of a dopant atom we used a simple model which describes the effects in terms of switching on and off a channel for resonant tunneling ( [2] and see e.g. [14]).…”

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Influence of resonant tunneling on the imaging of atomic defects on InAs(110) surfaces by low-temperature scanning tunneling microscopy

Depuydt

Maslova

Panov

et al. 1998

Applied Physics A: Materials Science & Processing

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The Scattering Theoretical Approach to the Scanning Tunneling Microscope

Doyen¹

1996

Scanning Tunneling Microscopy III

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In the interpretation of Scanning Tunneling Microscopy (STM) one often adopts the somewhat simplistic view that the tunnel current should be proportional to the local surface charge density at the position of the tip. More often than not this gives a reasonable interpretation of the STM -images. But in some cases it leads to an apparent contradiction with other available information on the sample surface. These contradictions are not always easy to resolve and some have been puzzling the STM-community for years.If STM is considered as a probe of the local sample charge density at the Fermi level, this suggests a comparison to results obtained from 2] where the total sample charge density is probed at distances which are roughly equivalent to those accessible by STM. Table 3.1 contains this comparison, which demonstrates that for clean and adsorbate covered close-packed metal surfaces there are problems in interpretating the STM images. For the given examples a picture of the local charge density differs qualitatively from the images seen in STM. In these cases the vertical coordinate of the probe tip that maintains a constant tunneling current will not coincide with what is usually imagined as the topography of the surface. The local charge density picture can be theoretically justified in the case of large tip-sample separation where the interaction between the two electrodes is negligible [3.3]. It is hence concluded that tip-sample interaction plays an important role in some STM-experiments and that a more general theory is needed to achieve a general understanding of the STM imaging process.A general theory has to reliably treat the quantum properties of electrons of a few eV kinetic energy. These electrons interact with structures of dimensions of the order of their wavelength. It has been recognized in the literature that realistic potentials and an exact solution of the three-dimensional scattering problem are required [3.4-8] In this article, theories of the Scanning Tunneling Microscope (STM) are reviewed which use a localized Green function approach to calculate the current beyond perturbation theory. The potential of the tip atom is expanded in a localized basis set. The scattering wave functions yielding the spatial current

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The Scattering Theoretical Approach to the Scanning Tunneling Microscope

Doyen

1993

Scanning Tunneling Microscopy III

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Tunneling through adsorbate and thin films, induced conductivity, charge density waves

Cited by 8 publications

References 5 publications

Influence of resonant tunneling on the imaging of atomic defects on InAs(110) surfaces by low-temperature scanning tunneling microscopy

Influence of resonant tunneling on the imaging of atomic defects on InAs(110) surfaces by low-temperature scanning tunneling microscopy

The Scattering Theoretical Approach to the Scanning Tunneling Microscope

The Scattering Theoretical Approach to the Scanning Tunneling Microscope

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