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The physical and electrical properties of highly thermally conductive materials have long been of interest, especially to power electronics manufacturers for the improvement of device efficiencies by better substrate cooling. This thesis provides a resume of the findings on high thermal conductivity materials and reports in detail on the results of an investigation undertaken to evaluate the suitability of Anodized Aluminium as a high thermal conductivity substrate material. Special anodic film fabrication techniques were developed to produce substrates on which thick film components could be directly printed. These studies were implemented in conjunction with a selection of low temperature Thick Film (TF) conductor and resistor pastes (inks) to achieve the optimum combination of Anodized Aluminium substrate and paste system. Test circuits of these chosen pastes were then printed and fired on Anodized Aluminium, Aluminium Nitride, Beryllia, Porcelain on Steel and Alumina substrates. The circuits were used to investigate the physical and electrical properties of the substrates, such as thermal conductivity, thermal expansion, thermal coefficient of resistance, dielectric constant and adhesion of the pastes to the substrates. The resultant anodized aluminium substrates were shown to:- be insulating to over 500 volts, able to withstand firing temperature of 500°C, and have a thermal conductivity very close to that of aluminium (240Wm-1K"1 at room temperature). Unfortunately electrical measurements have shown the anodic films to be humidity dependent, as the resistivity of the films is greatly reduced by an increase in humidity. The substrates are compatible with Heraeus C180-5554 conductor paste and the ESL 15511 resistor paste series. A low power hybrid device with surface mounted components was employed to validate the substrate/paste combinations. To conclude, this thesis has shown that anodized aluminium is suitable as a high thermal conductivity substrate for high power hybrid microelectronics.

Forward focussing of medium energy Auger and photoelectrons have been used along with LEED and Auger electron spectroscopy to investigate the initial stages of growth of both Cr and Co on Ag(001). Cr was found to grow epitaxially on Ag in the bcc phase up to ~2ML, in agreement with previous results. Co also grows epitaxially on Ag up to 3ML although it is proposed that the Co lattice is in the FCC phase but no comment can be made as to whether the overlayer is laterally expanded. Polarised Neutron Reflection measurements have been made on Ag/Cr/Ag sandwich structures with varying thicknesses of Cr. It is shown that for Cr thicknesses of 2 and 3.3ML the Cr is ordered non-ferromagnetically and it is proposed that at these thicknesses the Cr has reverted to its bulk antiferromagnetic order. However measurements on samples with Cr thicknesses of 0.33ML indicate ferromagnetic ordering with a greatly enhanced magnetic moment per atom over the bulk Cr value, in partial agreement with previous theoretical predictions. PNR measurements on a Ag/Fe/Ag (001) structure with thickness of Fe of 8ML have yielded an accurate measurement of the magnetic moment per atom for the Fe film of 1.0 +; 0.15microB, indicating a reduced value from that of bulk Fe of 2.22microB. x-ray scattering from a Ge (001) surface has been used to show that the surface undergoes a reversible phase transition at T = 954 +; 7K. It is proposed that the transition occurs due to the formation of vacancy-adatom pairs as some of the surface dimers break with increasing temperature. The data is explained in terms of a three level model used to describe the vacancy-adatom creation. The three level model results are compared with results from a simple Monte-Carlo simulation and an energy of 0.41 +; 0.05eV is deduced as the energy required to break the dimer bonds on the surface of Ge (001). Further X-ray scattering from a miscut Ge (001) surface shows that the surface is made up of regularly spaced steps of double atomic height, in agreement with theoretical and previous experimental studies. It is shown that perpendicular to the steps the reconstructed domains are limited in dimension by the steps, although both orientations of the reconstruction are possible.

The surface sensitive techniques of LEED, Auger electron spectroscopy (AES), ultra-violet photoelectron spectroscopy (UPS) and electron energy loss spectroscopy (EELS) were combined in order to study the electronic structure of well characterised overlayers of Pb, T? and Mn on Cu(l00). LEED and AES showed that Pb and T? atoms are adsorbed initially in linear chains lying in the (001) furrows between rows of copper atoms in the substrate surface. Both overlayers form an hop structure at the dense monolayer coverage. Thallium forms an intermediate overlayer structure in which the linear chains have moved closer together. Beyond the dense monolayer coverage both overlayers grow in the Stranski- Krastanov mode. In the case of Pb on Cu(l00) the LEED and AES results confirm the results of earlier work (Sepulveda and Rhead, 1977). Manganese initially forms a c(2 x 2) structure which is interpreted as an overlayer with Mn atoms lying in four-fold hollow sites. Further growth occurs in a disordered layer by layer mode. UPS shows that Pb and T? atoms are bonded mainly by the interaction of their 6s-p electrons with the Cu 4s-p electrons. There is little interaction between the overlayer 6s-p electrons and the Cu 3d electrons. In the case of T?, an analysis of work function measurements shows that the linear chains formed at low coverages do not interact appreciably with each other, whereas there is a strong interaction between the chains when they move closer together to form the next ordered overlayer. The transition from the first ordered T? overlayer structure to the second therefore involves a transition from a one dimensional to a two dimensional electronic interaction. For Mn overlayers there is a strong interaction between the Mn and Cu 3d electrons. At low coverages (?0.25 monolayers) a resonant bound state is observed just above the Cu 3d bands in agreement with a recent calculation. Such a state has not been observed in previous photoemission studies of dilute CuMn alloys. The photoemission spectra of thick Mn overlayers resemble the density of states of bulk Mn. EELS shows that Pb overlayers perturb the Cu 4s band confirming that bonding of the overlayer occurs via the Cu 4s orbitals. The existing models of plasmons in overlayers fail to predict the energies of the discrete losses observed in the EEL spectra of Pb and T? overlayers.

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