Arbitrary tip orientation in STM simulations: 3D WKB theory and application to W(110)

Gábor Mándi, Norbert Nagy, K. Palotás

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

We extend the orbital-dependent electron tunnelling model implemented within the three-dimensional (3D) Wentzel-Kramers-Brillouin (WKB) atom-superposition approach for simulating scanning tunnelling microscopy (STM) by including arbitrary tip orientations. The orientation of the tip is characterized by a local coordinate system centred on the tip apex atom obtained by a rotation with respect to the sample coordinate system. The rotation is described by the Euler angles. Applying our method, we highlight the role of the real-space shape of the electron orbitals involved in the tunnelling, and analyse the convergence and the orbital contributions of the tunnelling current above the W(110) surface depending on the orientation of a model tungsten tip. We also simulate STM images at constant-current condition, and find that their quality depends very much on the tip orientation. Some orientations result in protrusions on the images that do not occur above W atoms. The presence of such apparent atom positions makes it difficult to identify the exact position of surface atoms. It is suggested that this tip orientation effect should be considered in the evaluation of experimental STM images on other surfaces as well. The presented computationally efficient tunnelling model could prove to be useful for obtaining more information on the local tip geometry and orientation by comparing STM experiments to a large number of simulations with systematically varied tip orientations.

Original languageEnglish
Article number445009
JournalJournal of Physics Condensed Matter
Volume25
Issue number44
DOIs
Publication statusPublished - Nov 6 2013

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Scanning tunneling microscopy
scanning tunneling microscopy
Atoms
simulation
atoms
Tungsten
Electron tunneling
orbitals
electron orbitals
electron tunneling
Geometry
Electrons
tungsten
apexes
Experiments
evaluation
geometry

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Materials Science(all)

Cite this

Arbitrary tip orientation in STM simulations : 3D WKB theory and application to W(110). / Mándi, Gábor; Nagy, Norbert; Palotás, K.

In: Journal of Physics Condensed Matter, Vol. 25, No. 44, 445009, 06.11.2013.

Research output: Contribution to journalArticle

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