Surface tension effects in tunneling microscopy

Abstract

Induced electric charge lowers the surface tension of the substrate below the tunneling tip and creates a sharp surface tension gradient in its vicinity. For mercury as the substrate, the random waving is amplified by the gradient of the surface tension, resulting in observable mechanical ‘‘waving’’ of the surface that increases with the applied bias voltage. Its amplitude reaches a minimum at the potential of zero charge. In agreement with the Gibbs–Lippmann equation these effects are mitigated by the presence of adsorbed films but may lead to translocation of adsorbates by the biased tunneling tip.