Inhaltszusammenfassung

This thesis demonstrates the time-resolution of the electrical conduction in 2 to 100 nm thin iron films to the point where the 7 to 30 fs short lag between applied electric field and resulting current is measured with ca. 1 fs accuracy. I achieve this time resolution by improving the method of substrate referenced transmission terahertz time domain spectroscopy by correcting for the thickness difference between the substrate supporting the metal film and the reference substrate. The achieved...This thesis demonstrates the time-resolution of the electrical conduction in 2 to 100 nm thin iron films to the point where the 7 to 30 fs short lag between applied electric field and resulting current is measured with ca. 1 fs accuracy. I achieve this time resolution by improving the method of substrate referenced transmission terahertz time domain spectroscopy by correcting for the thickness difference between the substrate supporting the metal film and the reference substrate. The achieved time-resolution allows measuring how the lag depends on the thickness of the metal film. The significant difference between this thickness scaling of the lag and the thickness scaling of the direct current conductivity disproves Drude’s assumption of a universal relaxation time, which would imply the same scaling of both quantities. Therefore, I derive a description of the conduction dynamics in the framework of the semi-classical Bloch-Boltzmann formalism, resulting in the picture of a distribution of microscopic relaxation times. This picture of a relaxation time distribution allows interpreting the observed lag in terms of the average and the variation of the microscopic relaxation times. The accurate determination of the lag between applied field and resulting current in a metal, adds a second macroscopic observable to electronic transport and the relaxation time distribution picture relates this observable to microscopic relaxation processes in the metal. Thereby the improved substrate referenced transmission terahertz time domain spectroscopy can test microscopic theories of conduction more conclusively and will advance our understanding of transport processes in metals in general and in thin films in particular.» weiterlesen» einklappen

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Klassifikation

DDC Sachgruppe:
Physik