6 research outputs found
Interaction between electronic structure and strain in Bi nanolines on Si(001)
Heteroepitaxial strain can be a controlling factor in the lateral dimensions
of 1-D nanostructures. Bi nanolines on Si(001) have an atomic structure which
involves a large sub-surface reconstruction, resulting in a strong elastic
coupling to the surrounding silicon. We present variable-bias STM and first
principles electronic structure calculations of the Bi nanolines, which
investigates this interaction. We show that the strain associated with the
nanolines affects the atomic and electronic structure of at least two
neighbouring Si dimers, and identify the mechanism behind this. We also present
partial charge densities (projected by energy) for the nanoline with clean and
hydrogenated surroundings and contrast it to the clean Si(001) surface.Comment: 10 pages, 3 figures, submitted to Surface Scienc
Split-off dimer defects on the Si(001)2x1 surface
Dimer vacancy (DV) defect complexes in the Si(001)2x1 surface were
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 pi-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.Comment: 8 pages, 7 figures, submitted to Phys. Rev.