Wave-Function Mapping of InAs Quantum Dots by Scanning Tunneling Spectroscopy

Maltezopoulos, Theophilos; Bolz, A.; Meyer, Christian F.; Heyn, Ch.; Hansen, W.; Morgenstern, Markus; Wiesendanger, R.

doi:10.1103/physrevlett.91.196804

Cited by 129 publications

(147 citation statements)

References 28 publications

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“…26,27 In the present case, the substantial separation between the neighboring QDs produces this limitation in the transport of the electrons. (It should be noted that our QDs and surrounding GaAs are undoped, in contrast to the substantial doping employed by some other workers in which case transport of the carriers from a QD to the surrounding semiconductor can readily occur 9,13 ). However, the current flowing through the QD when the tip is positioned 4 nm away from the dot center is about 50 times less then when the tip is right above the dot center (1.2 pA vs. 70 pA), and in the former case the current transport is apparently efficient enough to prevent any significant charging (broadening).…”

Section: B Electronic Spectroscopymentioning

confidence: 99%

Size, shape, composition, and electronic properties of InAs/GaAs quantum dots by scanning tunneling microscopy and spectroscopy

Gaan

Feenstra

et al. 2010

Journal of Applied Physics

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InAs/GaAs quantum dot heterostructures grown by molecular-beam epitaxy are studied using cross-sectional scanning tunneling microscopy and spectroscopy. The images reveal individual InAs quantum dots (QDs) having a lens shape with maximum base diameter of 10.5 nm and height of 2.9 nm. Analysis of strain relaxation of the QDs reveals an indium composition varying from 65% at the base of the QD, to 95% at its center, and back to 65% at its apex. Room-temperature tunneling spectra acquired 3-4 nm from the center of a dot show a peak located in the upper part of the GaAs bandgap originating from the lowest electron confined state of the QD, along with a tail in the conductance extending out from the valence band and originating from QD hole states. A computational method is developed for simulating the tunneling spectra using effectivemass bands treated in an envelope-function approximation. By comparison of the computations to low-current spectra, the energy of the lowest electron and highest hole QD states are determined. These energies are found to be in reasonably good agreement both with optical measurements and prior theoretical predictions of Wang et al. [Phys. Rev. B 59, 5678 (1999)].

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Section: B Electronic Spectroscopymentioning

confidence: 99%

Size, shape, composition, and electronic properties of InAs/GaAs quantum dots by scanning tunneling microscopy and spectroscopy

Gaan

Feenstra

et al. 2010

Journal of Applied Physics

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“…particularly for relatively small dots in which discrete confined state features are expected to occur in the measured spectrum. In two exceptional works, 5,6 discrete electron and hole confined states have been observed by low-temperature STM/S. But even in these cases the energies of electron and hole QD states were not quantitatively determined, partly because of spectral distortion arising from tip-induced band bending in the semiconductor.…”

mentioning

confidence: 99%

“…Scanning tunneling microscopy (STM) has been used in many prior studies to probe the structural aspects of QDs, both in plan-view for viewing uncapped dots and in cross-section for viewing capped dots. 2,3,4,5,6,7,8 Scanning tunneling spectroscopy (STS) measurements during such studies are less common, and in some cases these works describe simply a reduced band gap associated with the dots. 2,3,8 A detailed interpretation of this band gap reduction is not clear i.e.…”

mentioning

confidence: 99%

Electronic states of InAs/GaAs quantum dots by scanning tunneling spectroscopy

Gaan

Feenstra

et al. 2010

Applied Physics Letters

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InAs/GaAs quantum-dot heterostructures grown by molecular-beam epitaxy are studied using cross-sectional scanning tunneling microscopy and spectroscopy. Individual InAs quantum dots (QDs) are resolved in the images. Tunneling spectra acquired 3-4 nm from the QDs show a peak located in the upper part of the GaAs bandgap originating from the lowest electron confined state, together with a tail extending out from the valence band from hole confined states. A line-shape analysis is used to deduce the binding energies of the electron and hole QD states.Published in Appl. Phys. Lett. 97, 123110 (2010).

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“…34 Thus, we cannot ascribe the localized states of the Ge nanoclusters to the quantum confinement of free charge carriers inside the nanoclusters. 35 …”

Section: B Si and Ge Growthmentioning

confidence: 99%

Self-assembly of periodic nanoclusters of Si and Ge along atomically straight steps of a vicinal Si(111)

Sekiguchi

Yoshida

Shiren

et al. 2007

Journal of Applied Physics

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The very initial stage of the molecular beam epitaxy of Si and Ge on Si͑111͒ −7ϫ 7 substrates with atomically straight steps has been studied by scanning tunneling microscopy and spectroscopy. The atomically straight steps have been prepared on a miscut Si͑111͒ substrate by annealing at 830°C with kink-up direct current. The length of the steps can be maximized by selecting a proper annealing time. The steps have a well-defined U͑2, 0͒ step-edge structure. The growth of both Si and Ge at temperatures between 250 and 400°C starts with formation of a single-adatom-row nanowire ͑0.67 nm in width͒ along the lower edge of each U͑2, 0͒ step. Subsequent growth of Si and Ge at temperatures between 250 and 300°C results in formation of one-dimensional arrays of nanoclusters ͑less than 2.0 nm in width͒ in the unfaulted halves of the 7 ϫ 7 structure along the upper step edges. Scanning tunneling spectroscopy reveals localized electronic states of the nanoclusters. Differences between the growth of Si and Ge nanoclusters are discussed.

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Wave-Function Mapping of InAs Quantum Dots by Scanning Tunneling Spectroscopy

Cited by 129 publications

References 28 publications

Size, shape, composition, and electronic properties of InAs/GaAs quantum dots by scanning tunneling microscopy and spectroscopy

Size, shape, composition, and electronic properties of InAs/GaAs quantum dots by scanning tunneling microscopy and spectroscopy

Electronic states of InAs/GaAs quantum dots by scanning tunneling spectroscopy

Self-assembly of periodic nanoclusters of Si and Ge along atomically straight steps of a vicinal Si(111)

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