The measured intensities of 14 diffracted beams of low-energy (30E240 eV) electrons normally incident on InAs(110) are reported. The temperature of the InAs surface during the measurements was T=110 K. The surfaces were prepared by ion-bombardment and annealing cycles followed by a verification of surface stochiometry (to within 10%) via Auger electron spectroscopy. Two separate crystals were examined in two separate vacuum instruments in order to verify the reproducibility of the intensity data. The data were analyzed using a relativistic, Hara-exchange electronion-core potential and an x-ray R-factor structure-analysis methodology. This analysis leads to the best-fit structure of InAs(110) being a rotation of the uppermost layer with the As rotated outward and the In inward. The second layer also is reconstructed with the In being displaced upward by 0.070.1 relative to its position in the bulk and the As being displaced downward by an equal amount. The x-ray R factor for the best-fit structure is Rx=0.23. This structure gives a satisfactory visual description of the measured intensities. For bond-length-conserving top-layer rotations the angle between the plane of the surface In-As chains and the plane of truncated bulk surface is 1=31°3°, in accordance with expectations based on correlations of covalent radii with prior zinc-blende-structure compound-semiconductor surfaces. The structure of InAs(110) provides the first test of these correlations. The best-fit R-factor structure corresponds to reduced relaxation parallel to the surface of the top-layer As relative to that for the bond-length-conserving structure. This best-fit structure is, however, equivalent to its bond-length-conserving counterpart (1=31°) to within the accuracy of the R-factor methodology.
ASJC Scopus subject areas
- Condensed Matter Physics