Regensburg 2007 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 12: Nanostructures at Surfaces II (Wires, Tubes)

O 12.4: Vortrag

Montag, 26. März 2007, 15:00–15:15, H36

Screening of electric field by a two-dimensional surface nanostructure — •Josef Mysliveček, Anna Stróźecka, Neelima Paul, and Bert Voigtländer — Institut für Bio- und Nanosysteme (IBN 3), and Center of Nanoelectronic Systems for Information Technology (CNI), Forschungszentrum Jülich, 52425 Jülich, Germany

A monolayer of Ge embedded in Bi-terminated Si(111) surface can form two-dimensional surface nanostructures like nanowires and nanorings [1]. We study the electronic properties of these nanostructures by scanning tunneling spectroscopy. Both the Bi-terminated Si(111) surface and the Ge areas feature a surface bandgap. On the Ge areas, however, the bandgap is smaller due to an electron state localized in the Ge-Si interface at an energy above the bulk valence band maximum [2]. We show that the electric field of the STM tip can depopulate this electron state creating a positive surface charge layer located on the Ge areas. Thus, the Ge areas screen the external electric field more efectively than the clean Bi-terminated Si(111) surface. This can be used e.g. to locally prevent the field-induced inversion of carriers in the subsurface region and to influence the surface conductivity on the nanoscale.

[1] M. Kawamura, N. Paul, V. Cherepanov, B. Voigtländer, Phys. Rev. Lett. 91, 096102, 2003.

[2] R.H. Miwa, T.M. Schmidt, P. Venezuela, Phys. Rev. B 72, 125403, 2005.