ELECTROSTATIC TIP-SURFACE INTERACTION IN SCANNING FORCE MICROSCOPY - A CONVENIENT EXPRESSION USEFUL FOR ARBITRARY TIP AND SAMPLE GEOMETRIES

The electrostatic energy between a dielectric scanning force microscop e (SFM) tip and a point charge is obtained in closed form as a functio n of the separation of the two objects. Applications of this result to both spherical and arbitrary tip shapes are discussed. Also, utilizin g kinematic data, a method is given to experimentally extract the forc e due to the tip-sample interaction from a typical SFM instrument. Thi s is done by analyzing the time dependent motion of the tip. The resul t is based on the use of a time dependent analysis of the force distan ce curve which is unavoidable in motion regimes in which the tip accel erates, as in the snap-to-contact process. (C) 1997 American Vacuum So ciety.