Effect of atomic force in STM

This fundamental relation can be extended to the many-body case, and a correlation between the interatomic force in the attractive-force regime and the tunneling conductance can be established. For metals, an explicit equation between two sets of measurable quantities is derived. Of course, the simple relation between the measured force and measured tunneling conductance is not valid throughout the entire distance range. First, the total force has three components, namely, the van der Waals force, the resonance force, and the repulsive force. Second, the actual measurement of the force in STM and 

AFM is further complicated by the deformation of the tip and sample near the gap region (Teague, 1978 Coombs and Pethica, 1985 Chen and Hamers, 1991a). At very short tip-sample distances, the reading from the z piezo no more represents the gap displacement. Nevertheless, in the normal working distance range of STM, the dominant force is the resonance force, and the simple relation is valid. 

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The effect of atomic forces in STM was observed repeatedly by direct experiments. Before the invention of the STM, Teague (1978) already... 

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