Charge Transport Through Single-Molecule Junctions: Experiments and Theory

In the pursuit of down-sizing electronic components, the ultimate limit is the use of single molecules as functional devices. Molecules can also provide additional functionalities compared to semiconductors. Using synthetic chemistry, an almost endless choice of molecular structures and compositions is available. With the proper knowledge, one...

OPE3: A model system for single-molecule transport

In this dissertation, charge-transport through individual organic molecules is investigated. The single molecules are contacted with two-terminal mechanically controllable break junction gold electrodes and their electrical and mechanical behavior studied at room and low temperature.

Conformational and Spin Effects in Single-Molecule Electronic Transport

This dissertation presents the experimental work on singlemolecule charge transport, particularly on the aspects of spin and orbital conformational effects in singlemolecule junctions. In this dissertation, we employ and develop various singlemolecule techniques, the mechanically controlled break junction (MCBJ), thermoelectric electromigrated...

Quantum transport in superconducting hybrids: Molecular devices and layered materials

In this thesis we investigate superconducting hybrids made from two material systems, namely, molecules and layered materials. For studies of superconducting phenomena in molecular junctions we develop two platforms which rely on the superconducting proximity effect to preserve pre-existing nano-gap formation techniques and bonding chemistries....

Various aspects of quantum transport through single molecules: Amechanical break-junction study

This dissertation concerns transport measurements in single-molecule junctions using the mechanically controlled break junction (MCBJ) technique. It describes various aspects that play a role in charge transport through single molecules, in order to develop the necessary knowledge to ultimately develop electronic devices based on intrinsic...

Complexity of Electron Transport in Nanoscale Molecular Junctions

In this dissertation, we analyse the charge transport of nanoscale molecular junctions in mechanically controllable break junction (MCBJ) experiments. In particular, we focus on the characterization of molecular features going beyond the "single-peak" picture, that is, considering features in the measurements in addition to themost prominent one...

Single–molecule conductance measurements: Correlations between chemical design and electronic properties

This thesis is about measurements of the electrical properties of different families of molecules. The research was focused on fundamental questions of charge transport in organic molecules. With this aim, experiments were performed to shed light on the underlying transport mechanisms. For example, an important ingredient of the work concerned...

Charge transport in a zinc-porphyrin single-molecule junction

We have investigated charge transport in ZnTPPdT-Pyr (TPPdT: 5,15-di(p-thiolphenyl)-10,20-di(p-tolyl)porphyrin) molecular junctions using the lithographic mechanically controllable break-junction (MCBJ) technique at room temperature and cryogenic temperature (6 K). We combined low-bias statistical measurements with spectroscopy of the molecular...

Probing the local environment of a single OPE3 molecule using inelastic tunneling electron spectroscopy

We study single-molecule oligo(phenylene ethynylene)dithiol junctions by means of inelastic electron tunneling spectroscopy (IETS). The molecule is contacted with gold nano-electrodes formed with the mechanically controllable break junction technique. We record the IETS spectrum of the molecule from direct current measurements, both as a...

Single-Molecule Break Junctions Based on a Perylene-Diimide Cyano-Functionalized (PDI8-CN2) Derivative

In this letter, we report the single-molecule conductance properties of a cyano-functionalized perylene-diimide derivative (PDI8-CN 2 ) investigated with gold nano-electrodes. This molecule is of large interest for the fabrication of high-performance and air-stable n-type organic field-effect transistors. Low-bias experiments performed on...

Carbon-fiber tips for scanning probe microscopes and molecular electronics experiments

We fabricate and characterize carbon-fiber tips for their use in combined scanning tunneling and force microscopy based on piezoelectric quartz tuning fork force sensors. An electrochemical fabrication procedure to etch the tips is used to yield reproducible sub-100-nm apex. We also study electron transport through singlemolecule junctions...

Can one define the conductance of amino acids?

We studied the electron-transport properties of ten different amino acids and one dimer (di-methionine) using the mechanically controlled break-junction (MCBJ) technique. For methionine and cysteine, additional measurements were performed with the scanning tunneling microscope break-junction (STM-BJ) technique. By means of a statistical...

Magnetic Fingerprints in an All-Organic Radical Molecular Break Junction

Polycyclic aromatic hydrocarbons radicals are organic molecules with a nonzero total magnetic moment. Here, we report on charge-transport experiments with bianthracene-based radicals using a mechanically controlled break junction technique at low temperatures (6 K). The conductance spectra demonstrate that the magnetism of the diradical is...

A Mechanically Tunable Quantum Dot in a Graphene Break Junction

Graphene quantum dots (QDs) are intensively studied as platforms for the next generation of quantum electronic devices. Fine tuning of the transport properties in monolayer graphene QDs, in particular with respect to the independent modulation of the tunnel barrier transparencies, remains challenging and is typically addressed using...

Large Conductance Variations in a Mechanosensitive Single-Molecule Junction

An appealing feature of molecular electronics is the possibility of inducing changes in the orbital structure through external stimuli. This can provide functionality on the single-molecule level that can be employed for sensing or switching purposes if the associated conductance changes are sizable upon application of the stimuli. Here, we...

Mechanical Tuning of Through-Molecule Conductance in a Conjugated Calix[4]pyrrole

A conformationally flexible calix[4]pyrrole possessing a conjugated electronic structure (an N-substituted oxoporphyrinogen (OxP) related to porphyrin) was used to investigate the influence of mechanical stretching on the single-molecule conductance of these molecules using the mechanically-controlled break junction (MCBJ) technique. The...

Enhanced Separation Concept (ESC): Removing the Functional Subunit from the Electrode by Molecular Design

A new concept to improve the reliability of functional single molecule junctions is presented using the E-field triggered switching of Fe^IIbis-terpyridine complexes in a mechanically controlled break junction experiment as model system. The complexes comprise a push-pull ligand sensing the applied E-field and the resulting...