This thesis investigates the mechanically controlled break junctions, with a particular emphasis on elucidating the behaviour of molecular currents at room temperature. The core of this experimental investigation involves a detailed analysis of conductance, examining how it varies over time and with changes in the gap between electrodes. Additionally, this study thoroughly evaluates transmission properties, coupling effects, and current characteristics.
A pivotal aspect of the research was the meticulous current measurement, followed by carefully selecting optimal data sets. This process set the stage for an in-depth analysis of resonant tunnelling phenomena observed through a single channel. Notably, these experiments were conducted under open atmospheric conditions at room temperature. A significant finding from this study is the recognition that our current model requires refinement. This adjustment is necessary to more accurately encapsulate a broader spectrum of molecular transport mechanisms.
Furthermore, this work significantly advances our comprehension of quantum effects in single-molecule junctions, particularly concerning similar molecules to Corannulene extending to some organometallics. One of the essential disclosures is the identification of deviations in the transport model, primarily attributable to electron-electron interactions. This insight is crucial as it paves the way for developing a more comprehensive and precise model, enhancing our understanding of molecular-scale electronic transport.:List of Figures xi
List of Tables xiii
Acronyms xiii
Terminology xv
Symbols xvi
Abstract xvii
1 Introduction 1
1.1 Motivation and Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Molecular Electronics Background . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 RelatedWork, the State of Art . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.4 Structure of the work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2 Methods and Implementations 7
2.1 Mechanically Controlled Break Junctions Principle . . . . . . . . . . . . . . 8
2.1.1 Setups forMCBJ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1.2 Measurement Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.1.3 Electrical Diagramof theMeasurement . . . . . . . . . . . . . . . . . 15
2.1.4 Criteria to Select the Data . . . . . . . . . . . . . . . . . . . . . . . . 15
2.2 Experiment Realisation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3 Molecules and Transport 20
3.1 Molecules in the Scope of this Thesis . . . . . . . . . . . . . . . . . . . . . . 20
3.1.1 Fixation of pi-Conjugated Molecules on Gold Surfaces via Thiol Bond 20
i
3.2 Ballistic Transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.2.1 Tunnelling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.3 Single Level Model (SLM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.3.1 Chemical Nature of theMolecular Channels . . . . . . . . . . . . . . 24
3.4 TransportMechanisms inMolecules attached toMCBJ . . . . . . . . . . . . 25
4 Results and Discussions 28
4.1 Discussions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.1.1 Opening Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.1.2 HistogramfromtheMeasurements . . . . . . . . . . . . . . . . . . . 30
4.2 Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
4.2.1 Current in Toluene . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
4.2.2 Current in Corannulene . . . . . . . . . . . . . . . . . . . . . . . . . 44
4.2.3 Current in Fe+3 Salen . . . . . . . . . . . . . . . . . . . . . . . . . . 49
4.2.4 Current Measurement after Consecutive Opening - Case Study: Fe+3
Salen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
4.2.5 Single LevelModel - Case Study: Corannulene . . . . . . . . . . . . . 53
4.2.6 Lorentzian Distribution and Fitting in Salen organometallics and Corannulene
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
4.2.7 Single Level Model - Study of the case: Fe+3 Salen . . . . . . . . . . 66
4.3 Transmission and Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
4.3.1 Transmission and Coupling - Case Study: Fe+3 Salen . . . . . . . . . 70
4.4 Conclusive Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
4.4.1 Hypothesis of Scattering . . . . . . . . . . . . . . . . . . . . . . . . . 76
5 Conclusion and Further Work 78
5.1 The CurrentMeasurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
5.2 Further Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
A Current with Mean Normalization i
A.1 Categories ofMeasurements . . . . . . . . . . . . . . . . . . . . . . . . . . . ii
A.1.1 Measurements without hysteresis or very small . . . . . . . . . . . . . ii
A.1.2 Measurements with hysteresis . . . . . . . . . . . . . . . . . . . . . . vi
A.2 Measurements without Fitting . . . . . . . . . . . . . . . . . . . . . . . . . . xii
B Our best fits where the SLM fails xi
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:93344 |
| Date | 20 August 2024 |
| Creators | Schmidt, Giovanna Angelis |
| Contributors | Erbe, Artur, Moresco, Francesca, Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:masterThesis, info:eu-repo/semantics/masterThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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