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Non-linear Tunneling Spectroscopy in Scanning Tunneling Microscopy and its Applications


Zengin, Berk. Non-linear Tunneling Spectroscopy in Scanning Tunneling Microscopy and its Applications. 2024, University of Zurich, Faculty of Science.

Abstract

This thesis presents the development of an accelerated spectroscopy method that utilizes the nonlinearities in the junction of a scanning tunneling microscope, henceforth referring to it as the parallel spectroscopy (PS).

We start with describing the underlying principles of parallel spectroscopy, share simulated results and advance with the demonstration of the instrumentation efforts. Our methodology is validated on the model system Au(111), successfully replicating the established dispersion relation with a significantly reduced spectroscopy duration of only 20 milliseconds per location. The method’s applicability is further examined on more electronically intricate systems like superconducting Nb and NbSe2 where the superconducting gap is successfully measured, quantified and compared with conventional spectroscopy techniques.

Using PS, we measure the quasiparticle interference of Ag(111) and NbSe2. While we find good agreement with literature, the more subtle effects of electron-phonon coupling require a limitation of the energy range that is simultaneously measured, which we successfully demonstrate.

Leveraging the swift spectroscopy times of PS, we pioneer a method that yields a multidimensional data cube. This approach permits the simultaneous acquisition of energy-dependent decay lengths and QPI maps at various tip-sample separations on Au(111). Furthermore, we explore the effect of tip-sample geometry when measuring decay lengths and propose solutions to overcome related measurement artifacts.

In our exploration of Cu3Au(111), we encounter the unwanted growth of oxides from interstitial oxygen. We verify the origin from the bulk by first deliberately removing the oxide by hydrogen annealing and by the deliberate exposure of Cu3Au to oxygen. Of the two phases that we find from segregation, only the three-fold symmetric oxide can be grown by oxygen exposure. Lastly, the growth characteristics of Co islands on Cu3Au(111) has been studied, asserting their thermal stability at room temperature and up to 190 ℃.

Keywords: Scanning tunneling microscope, spectroscopy, method development, differential conductance, quasiparticle interference mapping, dispersion relation, growth studies

Abstract

This thesis presents the development of an accelerated spectroscopy method that utilizes the nonlinearities in the junction of a scanning tunneling microscope, henceforth referring to it as the parallel spectroscopy (PS).

We start with describing the underlying principles of parallel spectroscopy, share simulated results and advance with the demonstration of the instrumentation efforts. Our methodology is validated on the model system Au(111), successfully replicating the established dispersion relation with a significantly reduced spectroscopy duration of only 20 milliseconds per location. The method’s applicability is further examined on more electronically intricate systems like superconducting Nb and NbSe2 where the superconducting gap is successfully measured, quantified and compared with conventional spectroscopy techniques.

Using PS, we measure the quasiparticle interference of Ag(111) and NbSe2. While we find good agreement with literature, the more subtle effects of electron-phonon coupling require a limitation of the energy range that is simultaneously measured, which we successfully demonstrate.

Leveraging the swift spectroscopy times of PS, we pioneer a method that yields a multidimensional data cube. This approach permits the simultaneous acquisition of energy-dependent decay lengths and QPI maps at various tip-sample separations on Au(111). Furthermore, we explore the effect of tip-sample geometry when measuring decay lengths and propose solutions to overcome related measurement artifacts.

In our exploration of Cu3Au(111), we encounter the unwanted growth of oxides from interstitial oxygen. We verify the origin from the bulk by first deliberately removing the oxide by hydrogen annealing and by the deliberate exposure of Cu3Au to oxygen. Of the two phases that we find from segregation, only the three-fold symmetric oxide can be grown by oxygen exposure. Lastly, the growth characteristics of Co islands on Cu3Au(111) has been studied, asserting their thermal stability at room temperature and up to 190 ℃.

Keywords: Scanning tunneling microscope, spectroscopy, method development, differential conductance, quasiparticle interference mapping, dispersion relation, growth studies

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Additional indexing

Item Type:Dissertation (monographical)
Referees:Natterer Fabian D, Mangham-Neupert Titus, Chang Johan
Communities & Collections:07 Faculty of Science > Physics Institute
UZH Dissertations
Dewey Decimal Classification:530 Physics
Language:English
Place of Publication:Zürich
Date:14 May 2024
Deposited On:14 May 2024 10:37
Last Modified:23 May 2024 09:19
Number of Pages:137
OA Status:Green
  • Content: Published Version
  • Language: English