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Influence of atomic tip structure on the intensity of inelastic tunneling spectroscopy data analyzed by combined scanning tunneling spectroscopy, force microscopy, and density functional theory
University of Regensburg , Germany ; Kanazawa University, Japan.
Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE). (Condensed Matter Physics)ORCID-id: 0000-0003-2659-4161
University of Regensburg, Germany.
Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
Vise andre og tillknytning
2016 (engelsk)Inngår i: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 93, nr 16, artikkel-id 165415Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Achieving a high intensity in inelastic scanning tunneling spectroscopy (IETS) is important for precise measurements. The intensity of the IETS signal can vary by up to a factor of 3 for various tips without an apparent reason accessible by scanning tunneling microscopy (STM) alone. Here, we show that combining STM and IETS with atomic force microscopy enables carbon monoxide front-atom identification, revealing that high IETS intensities for CO/Cu(111) are obtained for single-atom tips, while the intensity drops sharply for multiatom tips. Adsorption of the CO molecule on a Cu adatom [CO/Cu/Cu(111)] such that the molecule is elevated over the substrate strongly diminishes the tip dependence of IETS intensity, showing that an elevated position channels most of the tunneling current through the CO molecule even for multiatom tips, while a large fraction of the tunneling current bypasses the CO molecule in the case of CO/Cu(111).

sted, utgiver, år, opplag, sider
2016. Vol. 93, nr 16, artikkel-id 165415
HSV kategori
Forskningsprogram
Fysik, Elektroteknik alt Electrical engineering
Identifikatorer
URN: urn:nbn:se:lnu:diva-46508DOI: 10.1103/PhysRevB.93.165415ISI: 000373878100002Scopus ID: 2-s2.0-84963756980OAI: oai:DiVA.org:lnu-46508DiVA, id: diva2:857071
Tilgjengelig fra: 2015-09-28 Laget: 2015-09-28 Sist oppdatert: 2017-12-01bibliografisk kontrollert
Inngår i avhandling
1. Modeling of non-equilibrium scanning probe microscopy
Åpne denne publikasjonen i ny fane eller vindu >>Modeling of non-equilibrium scanning probe microscopy
2015 (engelsk)Licentiatavhandling, med artikler (Annet vitenskapelig)
Abstract [en]

The work in this thesis is basically divided into two related but separate investigations.

The first part treats simple chemical reactions of adsorbate molecules on metallic surfaces, induced by means of a scanning tunneling probe (STM). The investigation serves as a parameter free extension to existing theories. The theoretical framework is based on a combination of density functional theory (DFT) and non-equilibrium Green's functions (NEGF). Tunneling electrons that pass the adsorbate molecule are assumed to heat up the molecule, and excite vibrations that directly correspond to the reaction coordinate. The theory is demonstrated for an OD molecule adsorbed on a bridge site on a Cu(110) surface, and critically compared to the corresponding experimental results. Both reaction rates and pathways are deduced, opening up the understanding of energy transfer between different configurational geometries, and suggests a deeper insight, and ultimately a higher control of the behaviour of adsorbate molecules on surfaces.

The second part describes a method to calculate STM images in the low bias regime in order to overcome the limitations of localized orbital DFT in the weak coupling limit, i.e., for large vacuum gaps between a tip and the adsorbate molecule. The theory is based on Bardeen's approach to tunneling, where the orbitals computed by DFT are used together with the single-particle Green's function formalism, to accurately describe the orbitals far away from the surface/tip. In particular, the theory successfully reproduces the experimentally well-observed characteristic dip in the tunneling current for a carbon monoxide (CO) molecule adsorbed on a Cu(111) surface. Constant height/current STM images provide direct comparisons to experiments, and from the developed method further insights into elastic tunneling are gained.

sted, utgiver, år, opplag, sider
Växjö: Linnaeus University, 2015. s. 80
Emneord
scanning tunneling microscopy, molecular dynamics, density functional theory, non-equilibrium Green's functions
HSV kategori
Forskningsprogram
Fysik, Kondenserade materians fysik
Identifikatorer
urn:nbn:se:lnu:diva-46448 (URN)978-91-87925-73-3 (ISBN)
Presentation
2015-09-17, Ny227, Kalmar Nyckel, Kalmar, 10:00 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2015-09-28 Laget: 2015-09-23 Sist oppdatert: 2018-01-10bibliografisk kontrollert

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