Techn. Universiẗat, Diss., 2001--Darmstadt.

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A study has been made of the properties of thin yttrium oxide dielectric films prepared by the electron beam evaporation of high purity Y₂O₃ powder. Films deposited on freshly cleaved NaCl crystals and on polished n-type silicon were examined in the electron microscope. The specimens were found to be polycrystalline, with a crystal size of the order of 100 Å. The structure was found to be essentially the same as found for bulk Y₂O₃. D.C. conduction measurements were made on films of various thicknesses. The characteristics were found to be bulk-limited, with the conductivity decreasing at lower pressures. An activation energy of 0.6 eV was found. The conduction mechanism was believed to be Poole-Frenkel emission of electrons from donor centers into the Y₂O₃ conduction band. The donor centers were believed to be interstitial yttrium atoms rather than oxygen vacancies because of the pressure dependence observed in conductivity. Step response measurements were made, and the results explained on the basis of a loss peak with a most probable relaxation time of 200 seconds. The relaxation of oxygen atoms dissolved in the anion defective Y₂O₃ lattice was assumed to be the mechanism. The results of step response and A.C. bridge loss measurements indicated that different relaxation mechanisms are dominant in different frequency ranges. Internal photoemission measurements were made on Al-Y₂O₃-Al sandwiches. The energy barrier between the electrodes was found to be trapezoidal, with barrier heights of 3.14 and 3.72 eV. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

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Nuclear and laser spectroscopy measurements have been conducted at the Ion Guide Isotope Separator On-Line, IGISOL-IV, JYFL laboratory, Jyvaskyla. Nuclear moments have been extracted for two ground and two isomeric states of neutron deficient yttrium, 85g,mY and 86g,mY. The mean square charge radii and moments have been extracted for all states, providing, for the first time, estimates of static and dynamic quadrupole deformations in these shape transitioning nuclei. A second laser spectroscopy experiment yielded the frequency shifts between all stable isotopes of ionic ytterbium in exotic (high-lying metastable) resonance lines. Atomic field and mass shift parameters in these (high purity) transitions have been evaluated. A discussion of the impact these parameters may have on the chemical homologue, nobelium, is presented. New measurements of charge-state dependent IGISOL fission production yields (of strontium, yttrium and zirconium) are reported in this thesis. For the first time, charge state dependent effects in relative isomeric to ground state production have been detected. Possible explanations for, and exploitation of, this unexpected phenomenon is presented. A new data acquisition (DAQ) system has been built at The University of Manchester. It has been designed to fully replace the current setup used for laser spectroscopy at the JYFL laboratory. The new hardware has been extensively tested off-line and is ready to be installed at the laser-IGISOL. To work in conjunction with the new DAQ, two graphical user interfaces (GUIs) have been created, to display and sort data online, and permit efficient data extraction. Both have been shown to perform at the level required for experimental on-line use. An updated report on the status of an electrostatic ConeTrap is presented. Improved (more realistic) simulations are now seen to be capable of reproducing experimentally observed results. Further computational effort on the ion optics has shown that improved containment and transport efficiency can be readily achieved. A new trap, featuring a larger rear electrode, promises a greatly increased ion survival. The next commissioning phase will see the construction and installation of this upgraded ConeTrap.

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