Recent Results
Adsorbate induced two dimensional electron gas
To perform STS on a two dimensional electron
gas (2DEG) we use the adsorbate induced 2DEG located close to the surface.
We characterize it by Photoelectron spectroscopy (UPS). Monitoring valence
band features (Fig. 1) allows to measure the band bending as a function
of adsorbate coverage (Fig. 2). Close to the Fermi level also the 2DEG
itself can be detected (Fig. 3). It shifts down with increasing coverage
leading to a tunable carrier density (1011cm-3-range).
The strong dispersion of InAs leads to a strong restriction of the 2DEG
peak with detection angle (Fig. 4). The subband energies are routinely
deduced from the 2DEG peak, but the 2DEG-dispersion has not been resolved.
Measurements with higher angular resolution are planned.
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| Fig. 1: UPS spectra (hn=13
eV) measured with different Nb-coverages on InAs(110). |
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| Fig. 2: Band bending as a function
of Nb-coverage (line) deduced from energy shift of valence band features
(symbols). |
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| Fig. 3: 2DEG-peak as a function
of Nb-coverage. The two subbands calculated from the band bending are indicated. |
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| Fig. 4: The 2DEG-peak from InAs(110)
covered with 0.5 % Fe |
Related Publications
M. Morgenstern, J. Wiebe, A. Wachowiak, M. Getzlaff, J. Klijn, L. Plucinks, R.L.Johnson, and R. Wiesendanger, Phys.Rev. B 65, 155325 (2002):
Co on p-InAs(110): An island induced two-dimensional electron system consisting of electron droplets.
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M. Getzlaff, M. Morgenstern, Chr. Meyer, R. Brochier, R.L. Johnson, and R. Wiesendanger, Phys. Rev. B 63, 205305 (2001):
Nb-induced two dimensional electron gas on n-InAs(110): anomalous coverage dependence.
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M. Morgenstern, M. Getzlaff, D. Haude, R.L. Johnson, and R. Wiesendanger, Phys. Rev. B 61, 13805 (2000):
Coverage Dependence of the Fe induced Fermi Level shift and the Two Dimensional Electron Gas on InAs(110).
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