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Title: The surface electronic and magnetic properties of rare earth silicides and iron nanoclusters using metastable de-excitation spectroscopy
Author: Woffinden, Charles
ISNI:       0000 0004 2684 0382
Awarding Body: University of York
Current Institution: University of York
Date of Award: 2010
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Metastable de-excitation spectroscopy (MDS) is a technique that probes the surface of materials using metastable atoms (in our case He 23S) to produce an electron energy spectrum that is characteristic of the surface’s electronic structure. structure. These metastable atoms can, additionally, be spin polarised, enabling the magnetic properties of a surface to be probed by comparing the electron emission yield produced by the two spin states of the incident metastable atoms relative to the magnetisation direction of the sample. The aim of this research project is to use and develop a current instrument capable of performing MDS and spin-polarised MDS (SPMDS). This instrument has been used for surface analysis to probe and characterise the electronic and magnetic surface properties of a variety of materials. In particular, the electronic characteristics of the reconstructions between rare earth silicide nanowires and the implications these have to the surface and nanowire formation has been investigated. The surface electronic and structural differences of 2-dimensional when compared to 3-dimensional rare earth silicides have been studied and compared to results from ultraviolet photoelectron spectroscopy (UPS) and density functional theory (DFT) to determine where particular states arise. A process of deconvoluting the MDS spectrum that arises from the resonance ionisation and Auger neutralisation spectrum to reveal the effective density of states has been demonstrated and compared to a DFT predicted density of states, and found to agree. The magnetic, electronic and structural properties of ferromagnetic iron nanoclusters deposited on silicon substrates have been investigated using a range of techniques including SPMDS and MDS. An asymmetry in the SPMDS spectrum has been observed with a large magnitude, suggesting an asymmetry in the spin-split density of states above the bulk iron value. All developments to the instruments are also detailed, including the construction of an in-situ magneto optic Kerr effect (MOKE) magnetometer.
Supervisor: Tear, Steve Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available