Hydrogen on Si(001): Paired Diffusion
This sequence was taken at a temperature of 650 K. The width of the
picture is around 18 nm. At this temperature, the hydrogen is paired up
on the silicon dimers. Where there is a gap in the hydrogen layer, the
pi-*antibonding orbital of the silicon dimer shows up bright. these
vacancies are the bright features being imaged here. These vacancies move
around from frame to frame; this is caused by the hydrogen on top of the
silicon moving from dimer to dimer.