Cl. Bai et al., GEOMETRIC AND ELECTRONIC-STRUCTURES OF NAGAAS, Journal of vacuum science & technology. A. Vacuum, surfaces, and films, 11(3), 1993, pp. 525-528
This article reports structural and electronic properties of sodium ad
sorbed on room-temperature GaAs(110) surface as observed with scanning
tunneling microscopy in an ultrahigh vacuum. In the low-coverage regi
me, Na adatoms reside on the bridge site encompassing one Ga and two A
s surface atoms to form linear chains along the [110BAR] direction. Th
e Na-Na nearest-neighbor distance in this low-density chain structure
is 8 angstrom. When the Na coverage was increased to approximately 0.0
9 ML (1 ML = 2 Na per substrate unit cell), the chains became slightly
disordered. Some of them were packed closer to form domains with loca
l 2 X 2 structure. None of high-density two-dimensional ordered struct
ures or low-density zigzag chains was observed, in contrast to the Cs/
GaAs (110) system. Additional Na adsorption resulted in the formation
of three-dimensional disordered clusters. The saturation coverage of N
a adsorption on the GaAs (110) surface was determined to be approximat
ely 0.1 ML. No evidence of metallic characteristics was found in the I
-V curves recorded over the various Na-covered surfaces.