Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology

Härtill 8 uppsatser Diss. (sammanfattning) Uppsala : Uppsala universitet, 2003 filosofie doktorsexamen Doctor philosophiae Fullerenes have been shown to constitute a prototypical building block for truly nanometer-sized devices and exotic nanounit-based materials, e.g., high-temperature superconductors. This makes the detailed understanding of fullerene electronic states in compounds and at interfaces of primary importance, since the high symmetry of the molecule greatly simplifies the starting point of the analysis. Carbon nanotubes, which combine one macroscopic with two nanoscopic dimensions, are perhaps of even greater practical interest. Angle-dependent electron spectroscopies have been employed in the present work to study these materials, characterizing their structure, bonding, and electronic states. For solid C 60 , the photoelectron angular distribution has been found to be essentially that of the free molecule, modified by solid state scattering; a similar distribution is found for K 3 C 60. The surface and bulk electronic structure of K 3 C 60 has been identified by angle-dependent core and valence photoelectron spectroscopy (PES) and x-ray emission spectroscopy. An insulating surface layer has been identified for this high-temperature superconductor. Angle-dependent valence PES is used to investigate the electronic states of C 60 /Al(110). Electron correlations are found to be the origin of the splitting observed in the molecular orbitals, which is quite sensitive to the molecular orientation. The components of the highest occupied molecular orbital are differentiated according to their overlap with the substrate. A rigid shift of valence- and core-levels has been observed even for ionic and covalent C 60 compounds, reflecting the efficient static polarizability screening of the molecule. The alignment of multi-walled carbon nanotubes has been investigated by x-ray absorption spectroscopy, using the spectral intensity ratio of π*- and *-resonances. Core level combined with valence PES shows that the degree of defect structure varies from position to position on the sample. Valence photoelectron spectra of defect-free sample spots closely resembles the total DOS of graphite. degree of Doctor of Philosophy Docteur ès lettres Fullerenes have been shown to constitute a prototypical building block for truly nanometer-sized devices and exotic nanounit-based materials, e.g., high-temperature superconductors. This makes the detailed understanding of