Split-off dimer defects on the Si(001)2X1 surface

R.M.S. Schofield, N. J. Curson, J. L. O'Brien, M. Y. Simmons, R. G. Clark, N. A. Marks, H. F. Wilson, G. W. Brown, M. E. Hawley

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Dimer vacancy (DV) defect complexes in the Si(001)2X1 surface are investigated using high-resolution scanning-tunneling microscopy and first-principles calculations. We find that under low-bias filled-state tunneling conditions, isolated "split-off" dimers in these defect complexes are imaged as pairs of protrusions, while the surrounding Si surface dimers appear as the usual "bean-shaped" protrusions. We attribute this to the formation of π-bonds between the two atoms of the split-off dimer and second-layer atoms, and present charge density plots to support this assignment. We observe a local brightness enhancement due to strain for different DV complexes and provide the first experimental confirmation of an earlier prediction that the 1+2-DV induces less surface strain than other DV complexes. Finally, we present a previously unreported triangular shaped split-off dimer defect complex that exists at SB-type step edges, and propose a structure for this defect involving a bound Si monomer.

Original languageEnglish
Article number085312
Pages (from-to)853121-853128
Number of pages8
JournalPhysical Review B - Condensed Matter and Materials Physics
Issue number8
Publication statusPublished - 1 Feb 2004
Externally publishedYes


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