Jy. Koo et al., DIMER-VACANCY DEFECTS ON THE SI(001)-2X1 AND THE NI-CONTAMINATED SI(001)-2XN SURFACES, Physical review. B, Condensed matter, 52(24), 1995, pp. 17269-17274
Dimer-vacancy defects on clean Si(001)-2 X 1 and Ni-contaminated Si(00
1)-2 X n surfaces are investigated by scanning tunneling microscopy (S
TM). The clean Si(001) surface shows the 2 X 1 reconstruction irrespec
tive of cooling rates faster than 150 degrees C/sec. On the Si(001)-2
X 1 surface with a surface dimer-vacancy density of 1.7%, the most abu
ndant dimer-vacancy defect is a randomly distributed one dimer vacancy
(1-DV) of the Wang-Arias-Joannopoulos model. Appreciable amounts of (
1+2)-DV and 2-DV are observed. The ordered defects on the Si(001)-2 X
n surface are mainly composed of (1+2)-DV and 2-DV. The real-space STM
images reveal that the dimer adjacent to the unrebonded side of 2-DV
is depressed by more than 0.5 Angstrom, representing the highly asymme
tric characteristics. A small amount of Ni contamination on Si(001) dr
astically increases the dimer-vacancy density from below 2% to above 2
0%.