Spin-Dependent Surface Characteristics of an Absorbed Hydrogen Atom under a Scanning Tunneling Microscope Environment–Atom Manipulation by Magnetic Field

Abstract

We investigate the electronic states of a scanning tunneling microscope environment using first principles molecular orbital calculations, explicitly including spin states. We employ a cluster model comprised of a silicon surface and an absorbed hydrogen atom under a gold probe tip. We find that spin multiplicity of the system drastically changes the potential energy surfaces of the absorbed atom between the surface and the probe. Under the gold probe tip, it is observed that the desorption energy for a hydrogen atom from the silicon surface decreases from 4.09 eV to 2.84 eV when an external electric field, biased sample-negative, is applied along the cluster axis with the value of 0.3 V/Å at the singlet spin state. At the triplet spin state, however, the barrier of the potential well completely disappears under the electric field, sample-negative bias, with the value of 0.1 V/Å, which induces atom transfer from the surface to the probe. We assume that the tip-sample distance is 6.0 Å.