Scanning tunneling spectroscopy of charge effects on semiconductor surfaces and atomic clusters

Maslova, N. S.; Oreshkin, S. I.; Panov, V. I.; Savinov, S. Yu.; Depuydt, A.; Haesendonck, Chris Van

doi:10.1134/1.567638

Cited by 16 publications

(12 citation statements)

References 9 publications

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“…When combined with scanning tunneling microscopy (STM) imaging, STS is a powerful tool for studying the influence of lattice defects and impurities on the local electronic structure. Magnetic impurities in normal metals [2] as well as superconductors [3] or defects in semiconducting materials [4][5][6][7] have been studied.…”

Section: Introductionmentioning

confidence: 99%

“…These interactions result in considerable shifts of the allowed energy levels, where deep lying levels may be driven through the Fermi level [13][14][15]. Localized states can not only be connected with the sample surface [6], but also appear at the tip apex [16]. Because the radii of the localized states are of the order of the contact area, the tunneling current in STM and STS experiments can be dominated by electron transport through one single localized state [17].…”

Section: Introductionmentioning

confidence: 99%

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Scanning tunneling microscopy and spectroscopy at low temperatures of the (110) surface of Te-doped GaAs single crystals

et al. 1999

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We have performed voltage dependent imaging and spatially resolved spectroscopy on the (110) surface of Te doped GaAs single crystals with a low temperature scanning tunneling microscope (STM). A large fraction of the observed defects are identified as Te dopant atoms which can be observed down to the fifth subsurface layer. For negative sample voltages, the dopant atoms are surrounded by Friedel charge density oscillations. Spatially resolved spectroscopy above the dopant atoms and above defect free areas of the GaAs (110) surface reveals the presence of conductance peaks inside the semiconductor band gap. The appearance of the peaks can be linked to charges residing on states which are localized within the tunnel junction area. We show that these localized states can be present on the doped GaAs surface as well as at the STM tip apex.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Scanning tunneling microscopy and spectroscopy at low temperatures of the (110) surface of Te-doped GaAs single crystals

et al. 1999

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“…-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.…”

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confidence: 99%

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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“…While the charging peaks (CPs) of the tip‐induced QD only slightly undulate along the line, the DCP continuously requires higher V tip , while moving away from the defect, due to the decreasing capacitance . Such charging peaks can be most conveniently mapped at voltages below the onset of the QD charging peaks (Figure (e)−(g)) leading to the well known lines surrounding the defect in increasing distance with increasing voltage . It is obvious that the shapes of these lines resemble the shape of the sharp edges in Figure (c), albeit on a smaller length scale.…”

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confidence: 95%

Graphene Quantum Dots Probed by Scanning Tunneling Microscopy

et al. 2017

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Scanning tunneling spectroscopy results probing the electronic properties of graphene quantum dots are reviewed. After a short summary of the study of squared wave functions of graphene quantum dots on metal substrates, we firstly present data where the Landau level gaps caused by a perpendicular magnetic field are used to electrostatically confine electrons in monolayer graphene, which are probed by the Coulomb staircase revealing the consecutive charging of a quantum dot. It turns out that these quantum dots exhibit much more regular charging sequences than lithographically confined ones. Namely, the consistent grouping of charging peaks into quadruplets, both, in the electron and hole branch, portrays a regular orbital splitting of about 10meV. At low hole occupation numbers, the charging peaks are, partly, additionally grouped into doublets. The spatially varying energy separation of the doublets indicates a modulation of the valley splitting by the underlying BN substrate. We outline that this property might be used to eventually tune the valley splitting coherently. Afterwards, we describe graphene quantum dots with multiple contacts produced without lithographic resist, namely by local anodic oxidation. Such quantum dots target the goal to probe magnetotransport properties during the imaging of the corresponding wave functions by scanning tunneling spectroscopy.

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Scanning tunneling spectroscopy of charge effects on semiconductor surfaces and atomic clusters

Cited by 16 publications

References 9 publications

Scanning tunneling microscopy and spectroscopy at low temperatures of the (110) surface of Te-doped GaAs single crystals

Scanning tunneling microscopy and spectroscopy at low temperatures of the (110) surface of Te-doped GaAs single crystals

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

Graphene Quantum Dots Probed by Scanning Tunneling Microscopy

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