Landolt-Börnstein - Group III Condensed Matter

Interaction of Radiation with Surfaces and Electron Tunneling · Figs. 24 - 36

Abstract

This chapter discusses scanning tunneling microscopy (STM) images of semiconductors includes germanium (Ge), gallium arsenide (GaAs) and graphite. Tunneling spectroscopy measurements on the Ge(001) surfaces with two occupied surface states at 0.9 eV and 2.7 eV below EF, and an unoccupied surface state at 0.9 eV above EF are observed. Tunneling spectroscopy measurements of the Ge(111 )c(2 x 8) reconstruction show occupied states near -1.6 and -0.8 eV and unoccupied states near +0.4 and +1.5 eV. In GaAs(100), the gallium-rich face shows a 4 x 2 or c(8 x 2) reconstruction, and the arsenic-rich face shows a 2 x 4 or c(2 x 8) reconstruction. The STM measurements show that the surface atoms pair together, forming arsenic dimers. STM images of GaAs(110) obtained at positive sample bias reveal the positions of the unoccupied states concentrated on the Ga atoms, while images at negative bias reveal the occupied states concentrated on the As atoms. The GaAs(111)-A surface exhibits a 2 x 2 reconstruction. STM images at positive sample bias are interpreted as revealing the locations of the Ga atoms. Graphite is a rather unusual material due to its 2-dimensional layer structure. STM image of graphite acquired under ultrahigh vacuum conditions with a clean tip, along with a superimposed unit cell for scale is shown. STM images of graphite routinely observe only half the surface-layer atoms.

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Title
Interaction of Radiation with Surfaces and Electron Tunneling · Figs. 24 - 36
Book Title
Interaction of Radiation with Surfaces and Electron Tunneling
In
9.2.2.2 Semiconductors
Book DOI
10.1007/b51875
Chapter DOI
10.1007/10119615_68
Part of
Landolt-Börnstein - Group III Condensed Matter
Volume
24D
Editors
  • G. Chiarotti
  • Authors
  • R. J. Hamers
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