Interaction measurements between a tip and a sample in proximity regions controlled by tunneling current in a UHVSTM-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. (C) 1999 Elsevier Science B.V. All rights reserved.