The voltage between tip and sample in a scanning tunneling microscope (STM) results in a large electric field localized near the tip apex. The mechanical stress due to this field can cause appreciable deformation of both tip and sample on the scale of the tunnel gap. We derive an approximate analytical expression for this deformation and confirm the validity of the result by comparison with a finite element analysis. We derive the condition for a field-induced jump to contact of tip and sample and show that this agrees well with experimental results for material transfer between tip and sample by voltage pulsing in ultrahigh vacuum.
Physical Review Letters, 1998, Vol 81, Issue 25, p. 5572-5575