We investigated adsorbed Si dimers on Si(001) at similar to 100 degree
s C with atom-tracking STM to determine the effect of various local en
vironments on surface dynamics. Specifically, we find an asymmetry in
the dimer diffusion along a buckled A-type step. We also measure dimer
repulsion and attraction respectively from in-row and adjacent-row va
cancy defects. These findings lend insight into the nature of the dime
r-substrate bond and defect structure. (C) 1998 Published by Elsevier
Science B.V. All rights reserved.