Dresden 2006 – wissenschaftliches Programm

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O: Oberflächenphysik

O 5: Electronic structure I

O 5.4: Vortrag

Montag, 27. März 2006, 12:00–12:15, WIL A317

Neutral phosphorus atoms in Si(111)-2×1 stabilize local buckling of π-bonded chains — •J. K. Garleff¹, M. Wenderoth¹, R. G. Ulbrich¹, C. Sürgers², H. v. Löhneysen^2,3, and M. Rohlfing⁴ — ¹IV. Physikalisches Institut der Universität Göttingen, Friedrich-Hund-Platz. 1, 37077 Göttingen, Germany — ²Physikalisches Institut and DFG Center for Functional Nanostructures (CFN), Universität Karlsruhe, 76128 Karlsruhe, Germany — ³Forschungszentrum Karlsruhe, Institut für Festkörperphysik, 76021 Karlsruhe, Germany — ⁴School of Engineering and Science, International University Bremen, P. O. Box 750561, 28725 Bremen, Germany

Substitutional phosphorus (P) atoms in the Si(111)-2×1 surface have been studied with scanning tunneling microscopy at 8 Kelvin. The unexpected neutral charge state of embedded P atoms at low temperature has been established by experimental observation: (i) Peak positions in the differential conductance at the P atom and on the clean Si surface coincide. (ii) The P-induced contrast pattern is restricted to a single or double π-bonded chain. (iii) Atomic corrugation significantly changes around charged defects, but remains unaffected at P atoms. The absence of extra charge at substitutional P atoms in Si(111)-2×1 proves that its electronic properties are dominated by the surface states. The surface band gap of clean Si(111)-2×1 itself strongly decreases to higher temperature. This points on weaker buckling of the π-bonded chains at increased temperature. We explain the spectroscopic contrast of P atoms at room temperature [1] by a locally stabilized buckling of the π-chains.

[1] T. Trappmann et al., Europhys. Lett. 38, 177 (1997)