Interaction measurements between a tip and a sample in proximity regions controlled by tunneling current in a UHV STM–AFM

The interaction force–distance curves between a tip and a sample surface in close proximity were measured by logarithmically changing a tunneling current passing through them with a ultrahigh vacuum scanning tunneling microscopy–atomic force microscopy UHV STM–AFM.. Since the tunneling current changes exponentially with the separation between the tip and the sample, the separation can be controlled precisely and linearly by modulating a logarithmic target value fed into the STM feedback circuit to be a triangular waveform. A piezoresistive cantilever with a conductive Si tip was used after cleaning the tip by heating it in the UHV chamber. As a preliminary result, force-separation curves with reversible and irreversible jumps in close proximity were presented. q1999 Elsevier Science B.V. All rights reserved.