A new bridge technique for the measurement of the dielectric absorption of liquids and solutions at microwave frequencies has been described and its accuracy assessed. The dielectric data of the systems studied is discussed in terms of the relaxation processes contributing to the dielectric absorption and the apparent dipole moments. Pyridine, thiophen and furan in solution have a distribution of relaxation times which may be attributed to the small size of the solute molecules relative to the solvent. Larger rigid molecules in solution were characterized by a single relaxation time as would be anticipated from theory. The dielectric data of toluene, ethyl-, isopropyl- and t-butylbenzene as pure liquids and in solution were described by two relaxation times, one identified with molecular re-orientation and a shorter relaxation time.· The subsequent work was investigation of the possible explanations of this short relaxation process. Comparable short relaxation times were obtained from the analysis of the dielectric data of solutions of p-chloro- and p-bromotoluene below 40°C, o- and m-xylene at 25°C and 1-methyl- and 2 methylnaphthalene at 50 C. Rigid molecules of similar shapes and sizes were characterized by a single relaxation time identified with molecular re-orientation. Contributions from a long relaxation process attributed to dipolar origins were reported for solutions of nitrobenzene, benzonitrile and p-nitrotoluene. A short relaxation process of possible dipolar origins contributed to the dielectric absorption of 4-methyl- and 4-t-butylpyridine in cyclohexane at 25°C. It was concluded that the most plausible explanation of the short relaxation process of the alkyl-aryl hydrocarbons studied appears to be intramolecular relaxation about the alkyl-aryl bond. Finally the mean relaxation times of some phenylsubstituted compounds were investigated to evaluate any shortening due to contributions from the process of relaxation about the phenyl-central atom bond. The relaxation times of triphenylsilane and phenyltrimethylsilane were significantly short.

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Over the past decades, the continuous reduction in Si02/Si device dimensions has been approaching its technological and fundamental limits. This opens a possibility of novel channel materials and high-x dielectrics to be implemented for future CMOS field-effect transistors (FETs). Germanium has recently gained a lot of research interest due to its high electron and hole mobilities. Therefore, Si02, Ah03, and Hf02 materials are investigated as potential gate dielectrics for future germanium MOSFETs. Atmospheric pressure chemical vapour deposition technique is used to deposit Si02 on germanium, showing good results. The influence of an aluminium gate is experimentally demonstrated and the device performance of Si02/Ge devices is degraded during thermal treatment. The use of tungsten allows Si02/Ge capacitors to receive higher thermal treatment. Minority carrier lifetime is studied through low temperature capacitance-time measurements. Zerbst plots and linear approximation equation are used to determine carrier generation lifetime. Atomic layer deposition of Ah03 and Hf02 materials are also studied. Direct formation of Ah03 on germanium provides reasonable results. However, degradation of device performance is observed after thermal treatment, implying that a good interface layer is needed. In-situ plasma nitridation and thermal oxidation processes are developed to form GeOxNy and Ge02 interface layers, respectively. A high quality interface between germanium and Ge02 is observed, resulting in good electrical properties of capacitors with a Ge02 interface layer. Germanium MOSFETs are fabricated with Si02, Hf02 and Ah03 gate dielectrics with and without an interface layer. High electron (~1400 cm2N's) and hole mobilities (~540 cm2N•s) are experimentally demonstrated on devices with Si02 gate dielectric. However, low hole mobilities are observed on high-x/Ge transistors with and without GeOxNy interface layer, ~80-100 and ~160 cm2N•s, respectively. Consistent with the results observed on MOS capacitors, it is believed that high interface trap density is responsible for degradation of transistor performance.

Structure-property relationships in various 12- and IS-layer hexagonal perovskites have been investigated for use in Microwave Dielectric (MD) applications. Specifically; (i) the structural origin(s) of a peak in Er at 465 K for the 12-layer hexagonal perovskite Ba3LaNb3012, BLN, and its effect on the Temperature Coefficient of resonant Frequency, TCF; (ii) synthesis and structure-property relationships of related 12-layer hexagonal perovskites based on Ba3RENb)012 and Sr)RENbJOI2 with RE ions smaller than La3+ ; (iii) a study of the IS-layer hexagonal perovskite solid solution phase (Bas-xSrx)Nb4015 to establish if similar properties to BLN can be obtained and therefore improve our understanding of how octahedral tilting in hexagonal perovskites influences their microwave dielectric properties. (i) A study of the BLN crystal structure using mode analysis of Neutron Powder Diffraction, NPD data showed the structure to go from one with a tilted NbOIi network (space group RI) at 300 K to un-tilted (space group RIm) at 500 K. On cooling, the change in Nb06 framework at - 500 K causes displacement of the A-site cations from their ideal positions within the AO .• layers at - 465 K; it is this movement of A-site cations in response to octahedral tilting that gives rise to the peak in Er. Raman Spectroscopy, RS showed the loss of a peak (- 425 cm -I) at - 400 K that is associated with the phase transition. (ii) Ba,RENbJOl2 with RE = Pr3+ or Nd3+ did not exhibit resonance at microwave frequencies. Instead a relaxor-type response was observed from radio frequency measurements with a maximum in I::r near or below room temperature. NPD and RS data showed this behaviour is linked to size mismatch (cation variance) between the A-site cations. Sr3PrNb3012 showed encouraging microwave dielectric properties with I::r - 35, Q.f - 17,000 GHz and TCF - 8 ppm K-'. (iii) The (Bas_xSrx)Nb4015 study found materials that do show similar properties to BLN. Sr-rich members of this study vi can be described has having a tilted NbOf, network (space group PJe!) whereas the Ba- rich members contain untilted Nb06 octahedra (space group PJmJ) at room temperature. This change from a tilted to untilted structure as the Ba content increases leads to a crossover from a tilt to untilt system at room temperature for Ba2:;Sr2.sNb4015 (B2.5S2SNO). This crossover at B2.5S2.sNO is reflected in the room temperature er and TCF (Er - 47, TCF - 343 ppm K-1) which have their highest values for this composition. This provides confirmation of the effect octahedral tilting can have on MD properties. The trend in Q.f is obscured by extrinsic effects, for example as a result of an irregular ceramic microstructure (SrsNb40ls) and the presence of impurities that exist as intergrowths within the main phase. The analysis of the FWHM of M" Debye peaks from IS data was useful to detect electrical heterogeneity within the grains and could be used to link with Q.f. vii