This thesis describes the formation and physical properties of atomic chains consisting of metal atoms and incorporated small molecules. Small molecules like oxygen and hydrogen modify the... Show moreThis thesis describes the formation and physical properties of atomic chains consisting of metal atoms and incorporated small molecules. Small molecules like oxygen and hydrogen modify the electrical and mechanical properties of these wires, resulting in new one-dimensional conductors. Show less
Gold nanoparticles are spherical clusters of gold atoms, with diameters typically between 1 and 100 nanometers. The applications of these particles are rather diverse, from optical labels for... Show moreGold nanoparticles are spherical clusters of gold atoms, with diameters typically between 1 and 100 nanometers. The applications of these particles are rather diverse, from optical labels for biological experiments to data carrier for optical data storage. The goal of my project was to develop new methods to study the physical properties of single gold nanoparticles on ultra-short timescales. Exciation with a short laser pulse brings a nanoparticle out of equilibrium, which makes it vibrate with a period that depends on the particle diameter and the speed of sound in gold. The vibrational period of a gold nanoparticle with a diameter of 60 nanometer is 20 picoseconds. This acoustic vibration has been detected by us for the first time for single particles. The main advantage of single-particle studies over bulk detection of these particles lies in the fact that all particles in an ensemble vibrate at slightly different frequencies, which causes increased damping due to dephasing. The damping of the vibrations of single particles only depends on the elastic coupling between the particle and its environment, which offers the possibility of using these particles as mechanical nanosensors. Show less
The goal of this thesis is to study charge transport phenomena in organic materials. This is done optically by means of single-moleculespectroscopy in a field-effect transistor based on a molecular... Show moreThe goal of this thesis is to study charge transport phenomena in organic materials. This is done optically by means of single-moleculespectroscopy in a field-effect transistor based on a molecular crystal.We present (in Chapter 2) a fundamental requirement for single-moleculespectroscopy concerning the energy levels of the guest molecule withrespect to the ones of the host molecule. Following this constraint, westudy (in Chapters 3 and 4) the photophysics of a new system forhigh-resolution spectroscopy at cryogenic temperatures, which consistsof dibenzoterrylene molecules inserted in a crystal of anthracene. Wethen characterise (in Chapter 5) the electrical properties of theanthracene field-effect transistor with 'conventional' methods. In Chapter 6, wefinally use the influence of an electric field on the spectroscopicproperties of fluorescent molecules to investigate locally the chargecarrier transport phenomena in a crystal of anthracene.The goal of this thesis is to study charge transport phenomena inorganic materials. This is done optically by means of single-moleculespectroscopy in a field-effect transistor based on a molecular crystal.We present (in Chapter 2) a fundamental requirement for single-moleculespectroscopy concerning the energy levels of the guest molecule withrespect to the ones of the host molecule. Following this constraint, westudy (in Chapters 3 and 4) the photophysics of a new system forhigh-resolution spectroscopy at cryogenic temperatures, which consistsof dibenzoterrylene molecules inserted in a crystal of anthracene. Wethen characterise (in Chapter 5) the electrical properties of theanthracene field-effect transistor with 'conventional' methods. In Chapter 6, wefinally use the influence of an electric field on the spectroscopicproperties of fluorescent molecules to investigate locally the chargecarrier transport phenomena in a crystal of anthracene.The goal of this thesis is to study charge transport phenomena inorganic materials. This is done optically by means of single-moleculespectroscopy in a field-effect transistor based on a molecular crystal.We present (in Chapter 2) a fundamental requirement for single-moleculespectroscopy concerning the energy levels of the guest molecule withrespect to the ones of the host molecule. Following this constraint, westudy (in Chapters 3 and 4) the photophysics of a new system forhigh-resolution spectroscopy at cryogenic temperatures, which consistsof dibenzoterrylene molecules inserted in a crystal of anthracene. Wethen characterise (in Chapter 5) the electrical properties of theanthracene field-effect transistor with 'conventional' methods. In Chapter 6, wefinally use the influence of an electric field on the spectroscopicproperties of fluorescent molecules to investigate locally the chargecarrier transport phenomena in a crystal of anthracene. Show less
The central topic of the Thesis concerns light scattering experiments with entangled photons. Specifically, we study the effect of scattering processes on polarization-entanglement of twin-photons.... Show moreThe central topic of the Thesis concerns light scattering experiments with entangled photons. Specifically, we study the effect of scattering processes on polarization-entanglement of twin-photons. The main idea is that scattering generally couples polarization and spatial degrees of freedom of photons. The details of this coupling depend on the characteristics of the scattering medium. Such coupling, in turn, can reduce the entanglement of twin-photons, if the photon pairs are detected in a momentum-insensitive way. We have investigated a broad range of optical scattering media ranging from milk to polymer fibers. By manipulating the parameters of these samples we were able to generate a broad range of quantum states, proving for the first time that scattering processes are a substantial tool for mixed-state engineering. This is of great importance for quantum information since any real-world application thereof has to deal with mixed (as opposed to pure) states. Show less
