Accession Number:

ADA250726

Title:

GaAs(001) (2x4) Surface-Structure Studies with Shadow-Cone-Enhancement Secondary-Ion Mass Spectrometry

Descriptive Note:

Corporate Author:

PENNSYLVANIA STATE UNIV UNIVERSITY PARK DEPT OF CHEMISTRY

Report Date:

1992-03-15

Pagination or Media Count:

13.0

Abstract:

The atomic geometry of the GaAs 001 2 X 4 surface has been analyzed quantitatively by shadow cone-enhanced secondary-ion mass spectrometry. The technique is based on the concept that the shadow cone created by the interaction between an incident-ion beam and a surface atom focuses ion flux onto specific crystal coordinates. In this experiment, secondary Ga ions were desorbed by a 3-keV Ar--ion beam and were detected at an energy of 20 eV. The surface was prepared by molecular-beam epitaxy and transferred in situ to an UHV surface-analysis chamber. The microscopic mechanisms of the desorption process were elucidated by a three-dimensional molecular-dynamics computer simulation. The data analysis also involved comparing the incidence angles corresponding to enhanced intensity features in the secondary-Ga-ion yield with the angles determined in a two-body-interaction calculation using the Moliere approximation to the Thomas-Fermi potential. This study confirms the AS2-dimer structure of the GaAs001 2X4 surface, and the As-As bond length is determined to be 2.73 andor- 0.10 A. This value suggests that, analogous to the atoms in bulk As, the As2-dimer atoms are threefold coordinated. Within the precision of the analysis, no relaxations were observed in the second and deeper layers of the surface.

Subject Categories:

  • Inorganic Chemistry
  • Electrical and Electronic Equipment
  • Atomic and Molecular Physics and Spectroscopy
  • Nuclear Physics and Elementary Particle Physics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE