Charge transport in bottom-up inorganic-organic and quantum-coherent nanostructures

Abstract

This thesis is based on results obtained from experiments designed for a consistent study of charge transport in bottom-up inorganic-organic and quantum-coherent nanostructures. New unconventional ways to build elements of electrical circuits (like dielectrophoresis, wedging transfer and bottom-up fabrication using selective chemical interactions) were studied and are presented in this thesis. We also investigated the next steps in understanding fundamental physics phenomena such as charge transport through a pair of metallic Coulomb islands coupled in parallel, coherent transport through organic molecular monolayers and dynamical nonlocality in normal metals. In this thesis, we use diffusive systems as inorganic components (Au films, Au nanorods (NRs) and Au nanoparticles (NPs)), and self-assembled molecular layers as organic part in order to build hybrid devices. Chapter 1 gives a brief introduction to the charge transport through molecular layers and to the main phenomena in the diffusive regime. These are the Aharonov-Bohm (AB) effect, universal conductance fluctuations (UCF), and the Coulomb blockade which reveal the quantum and classical behaviour of electrons. Chapter 1 also describes experimental methods and techniques required to open the secrets of electron transport. Chapters 2-3 are dedicated to the two different methods (dielectrophoresis and wedging transfer techniques, respectively) of the molecular junction fabrication and the consistent study of the charge transport mechanisms through organic molecular layers. A unique bottom-up approach of the fabrication of single-electron transistors (SETs) is described in detail in chapter 4, followed by the investigation of the electronbehaviour in a pair of metallic Coulomb islands coupled via molecular barriers in parallel (Chapter 5). Chapter 6 discusses dynamic nonlocality in a diffusive system where AB effect is used as a switch to tune electron transport. In the end of the thesis (Chapter 7) we show an indication of the coherent electron transport in a hybrid inorganic-organic AB interferometer with embedded molecular junctions and propose novel geometries of hybrid AB rings for future studies of the coherence in organic molecules.