Investigating the effects of silicon tip contamination in noncontact /scanning force microscopy SFM

.We have studied the possible modifications to a noncontact scanning force microscopy SFM silicon tip due to adsorption of species from the gas phase and due to contact with a NaCl surface. A model of the tip was developed based on a 33 atom silicon cluster, and then the different adsorbates were added and changes to tip electrostatic properties investigated. The interaction of a silicon tip with a NaCl surface was modelled quantum mechanically, allowing us to calculate the charge state of the adsorbed chlorine ion in the process of separation of the two surfaces. q 1999 Elsevier Science B.V. All rights reserved