Regensburg 2004 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 3: Quantenpunkte und -dr
ähte: Herstellung und Charakterisierung
HL 3.8: Vortrag
Montag, 8. März 2004, 12:00–12:15, H17
Real Space Observation of Anisotropic Electron Scattering in a quasi 1d-System with a Point Scatterer — •J. K. Garleff1, M. Wenderoth1, R. G. Ulbrich1, C. Sürgers2, and H. v. Löhneysen2 — 1IV. Physikalisches Institut, Universität Göttingen, D-37077 Göttingen — 2Physikalisches Institut, SFB 195, Universität Karlsruhe, D-76128 Karlsruhe
The Si-(111)-2× 1 surface is described by the π-bonded chain model. Band structure calculations [1] reveal a strong anisotropy with a steep dispersion along the chains and almost no dispersion perpendicular to them. The free surface as well as near-surface donors have been investigated by STM and STS at T = 8 K with atomic resolution and a spectral width of Δ E ≈ 50 meV. In the vicinity of donors the local density of states (LDOS) shows a highly anisotropic contrast below EF. It extends ∼10 nm along the reconstruction and ∼1 nm perpendicular. For donors in the top layer only one chain is affected. The LDOS near the donor is increased by a factor 3-4 compared with the free surface value and shows a dip at the centre of the donor site, if the donor is close to the surface. We interpret the observations as the scattering of “quasi 1-dimensional”-electrons by the donor. The quasi-1d system is provided by the Si-(111)-2×1 surface band structure. Additional features near EF support these findings.
[1] M. Rohlfing and S. G. Louie, Phys. Rev. Lett. 83, 856 (1999)