Low temperature scanning tunneling spectroscopy on InAs(110)

Morgenstern, Markus; Haude, D.; Guðmundsson, Viðar; Wittneven, Chr.; Dombrowski, R.; Steinebach, C.; Wiesendanger, R.

doi:10.1016/s0368-2048(00)00112-2

Cited by 36 publications

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References 45 publications

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“…The InAs was cleaved in situ at a base pressure of 2ϫ10 Ϫ10 mbar resulting in a clean and smooth ͑110͒ surface. 12 Nb was deposited from an e-beam evaporator at a rate of 2ϫ10 Ϫ3 ML/s at a sample temperature of 300 K. The flux was calibrated by a quartz balance and is given with respect to the unit cell of InAs͑110͒ ͑1 ML means 1 Nb-atom per unit cell͒. Cross checks with STM and Auger electron spectroscopy ͑AES͒ revealed that the errors in the flux calibration were below 50%.…”

Section: Methodsmentioning

confidence: 99%

Nb-induced two-dimensional electron gas onn−InAs(110):Anomalous coverage dependence

et al. 2001

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Angle-resolved photoelectron spectroscopy was used to determine the coverage dependence of the Nbinduced Fermi-level shift and the formation of a two-dimensional electron gas ͑2DEG͒ on n-type InAs͑110͒. The maximum Fermi-level shift of 300 meV was achieved at a Nb coverage of 20%, which is a factor of 70 higher than expected from the surface doping model. Scanning tunneling microscopy images reveal the formation of Nb clusters ͑1-4 atoms͒ at room temperature, however, the resulting reduced Nb-Nb distance cannot explain the dramatically reduced ionization probability of the Nb atoms. We propose that hybridization of the donor levels in Nb clusters has to be taken into account to understand the coverage dependence. The coverage dependence of the 2DEG peak exhibits good agreement with a one-dimensional model of the confinement energy. A Nb coverage of 0.1% yields a 2DEG with only 1ϫ10 11 electrons/cm 2 giving a filling factor of one in magnetic fields as low as 2 T.

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Section: Methodsmentioning

confidence: 99%

Nb-induced two-dimensional electron gas onn−InAs(110):Anomalous coverage dependence

et al. 2001

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“…At sufficiently low voltage, the derivative of the integral is dominated by the integrand. Additional terms, which arise due to the fact that the derivative is by V and not by E, can be neglected if D tip (E) is structureless within the considered energy region [6]. One gets: dI=dVðr tip ; VÞ / D sample ðE À E F;sample ¼ eV; r tip Þ Á D tip ðE ¼ E F;tip Þ:…”

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“…This is usually not the case, but one can use simple normalization processes [6,14] to reconstruct the resulting dI=dV(x, y, V)-values at constant z.…”

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“…Thus, one measures the so called local density of states D surface (eV, x, y) at the energy corresponding to the applied voltage V, if a does not depend on (x, y). The latter can be checked by measuring the spatial dependence of IðzÞ / e ÀaÁz : It turns out that homogeneous samples usually exhibit a spatially constant a except at the atomic scale [6].…”

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“…However, a mostly depends only weakly on energy, if one measures at low voltage V with respect to the work function of tip and sample (4-5 eV). The error can be estimated to be lower than 10% at voltages below V ' 200 mV [6]. At higher voltage, an empirical formula is used to eliminate the influence of a [11]: The energy resolution DE can be measured using an isotropic superconductor such as Nb as one of the electrodes.…”

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Graphene is a truly two-dimensional (2D) material with exceptional electronic, mechanical, and optical properties. As such, it consists of surface only and can be probed by the welldeveloped surface science techniques such as, e.g., scanning tunneling microscopy (STM). This method bridges the gap between the surface science community and the electronic device community and might lead to novel combined approaches. Here, I review some of the STM and scanning tunneling spectroscopy (STS) experiments on monolayer graphene samples. I will concentrate on graphene samples deposited on insulating substrates, since these are related to graphene device concepts. In particular, I will discuss the morphology of graphene on SiO 2 and other emerging substrates, some nanomechanical manipulation experiments using STM, and spectroscopic results. The latter can map the disorder potentials as well as the interaction of the electrons with the disorder, which is most pronounced in the quantum Hall regime.Three-dimensional representation of a STM image of graphene; the atomic resolution is displayed as color code, while the rippling is shown in three dimensions (courtesy of M. Pratzer, RWTH Aachen).

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Low temperature scanning tunneling spectroscopy on InAs(110)

Cited by 36 publications

References 45 publications

Nb-induced two-dimensional electron gas onn−InAs(110):Anomalous coverage dependence

Nb-induced two-dimensional electron gas onn−InAs(110):Anomalous coverage dependence

Scanning Tunneling Spectroscopy

Scanning tunneling microscopy and spectroscopy of graphene on insulating substrates

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