The incipient stages of plasticity in KBr single crystals were examined in ultra-high

vacuum by means of atomic force microscopy and Kelvin probe force microscopy.

Conducting diamond-coated tips were used to both indent the crystals and image

the resulting plastic deformation. Kelvin probe force microscopy revealed that edge

dislocations intersecting the surface carry a negative charge similarly to kinks in surface steps, while screw dislocations showed no contrast. The charges were

attributed to trapped cation vacancies which compensate the charge of divalent

impurities. Furthermore, the site of indentation was found to carry a large positive

charge. Weak topographic features extending in the <110> direction from the

indentation were identified by atomic-resolution imaging to be pairs of edge

dislocations of opposite sign, separated by a distance similar to the indenter radius.

They indicate the glide of two parallel {110} planes perpendicular to the surface, a

process which allows for a slice of KBr to be pushed away from the indentation

site.

A Kelvin Probe Force Microscopy of Charged Indentation-Induced Dislocation

Structures in KBr. P.Egberts, T.Filleter, R.Bennewitz: Nanotechnology, 2009,

20[26], 264005