The observation of interaction forces on an atomic scale is discussed. We show that the sensitivity is essentially limited by thermal fluctuations and by instabilities which can arise for attractive interaction potentials. An experiment was designed in order to explore the forces acting between tunnel tip and sample during scanning tunneling microscopy (STM). Force gradients were detected as resonance shifts of cantilever beams used as sample stage. Beam deflections caused by force variations were also recorded. We present data for tungsten tips and polycrystalline silver surfaces prepared under UHV conditions. Large positive force gradients were found for the range of tunnel distances investigated. Force maps show pronounced features correlating directly with topographic structures.
By: U. Durig, J. K. Gimzewski, D. W. Pohl, R. Schlittler
Published in: RZ1523 in 1986
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