ISBN 978-3-8439-4968-2

978-3-8439-4968-2, Reihe Physik

Sven Velten
Phonon engineering in thin tin films for tuning photon-nuclei interaction

167 Seiten, Dissertation Universität Hamburg (2021), Softcover, A5

Zusammenfassung / Abstract

When materials are fabricated at the nanoscale, properties such as thermodynamic quantities can drastically deviate from bulk properties. Thereby, the embedding environment has a strong impact on the behavior of the nanostructured material and thus provides a handle to engineer the properties as desired. In this work, the vibrational behavior of embedded thin tin films is probed and engineered in order to tune the photon-nuclei interaction in nuclear resonance scattering. The fabrication of tin films is typically affected by tin clustering. Here, they are prepared by combining magnetron sputter deposition with vacuum quenching resulting in Beta-Sn films with roughnesses of below one nanometer. By employing nuclear resonance scattering at the 23.88 keV resonance of 119Sn, not only a deviating tin hyperfine structure is found at the interface to the embedding material, but also indications for a strong distortion of thermodynamic properties in the interface region. Thus, nuclear inelastic scattering is performed to access the phonon density of states of the tin films. A shift of the phonon modes to higher energy is measured reflecting an increase of the rigidness of the tin atoms. This results in an enhancement by up to a factor of eight of the Lamb-Mössbauer factor, a quantity describing the probability of an elastic nuclear resonant scattering process. In addition to tin films, also embedded thin films of stannic oxide are investigated for nuclear quantum optics. Embedded in magnesium oxide, the stannic oxide films exhibit a nearly ideal two-level quantum system independent of the layer thickness. Collective quantum optics effects such as the collective Lamb shift and superradiance are measured as a function of the tin dioxide layer thickness. The obtained results pave the way for applying thin tin films to probe spin structures in paramagnetic materials and to extend nuclear quantum optics to the resonance energy of 119Sn.