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The study of atoms and molecules on bulk insulating surfaces is of critical importance to many fields of surface science including lubrication, and molecular electronics. I studied these systems by using a variety of theoretical methods to predict adsorption geometry, diffusion pathways, and film structure, and to interpret noncontact atomic force microscopy (NCAFM) data. I began by using molecular dynamics (MD) simulations to predict that Pd atoms deposited onto MgO(100) exhibit some transient mobility. They were initially able to move across the surface, but were eventually captured at an adsorption site when enough energy had been dissipated. Similarly, deposited molecules may also be able move around and find nucleation sites such as step edges or kinks before becoming stabilized on surface terraces at low temperature. I then moved on to study the properties of single molecules on oxide surfaces. I combined my theoretical calculations with experimental data to compare adsorption sites and geometries of Co-Salen molecules on NaCl(100) and NiO(100). I used density functional theory calculations (DFT) to show that minor differences in commensurability between the molecule and the surface can qualitatively change adsorption. Both surfaces are bulk insulators with simple cubic crystal structures, however, a much higher adsorption energy and distortion of the molecule on NiO(100) produced a significant vertical dipole moment. Single molecules adsorbed onto insulators can be directly imaged with chemical resolution using metal coated NCAFM tips. However, accurate interpretation of the results is needed. I studied metallic tips using DFT calculations and developed a point dipole model to represent the Cr coated tips used experimentally. I then fit the position and magnitude of the point dipole in this model directly to experimental scan-lines and was able to produce virtual AFM (VAFM) images and scan-lines that were in quantitative agreement with experiment. This method simultaneously reduced the complexity of interpretation of experimental data and the computational cost of producing VAFM images. Finally, I studied larger systems using a hybrid quantum mechanics/molecular mechanics (QM/MM) and parametrized classical force fields using genetic algorithm (GA) methods. This allowed me to study CDB, a large organic molecule, on KCl(100). Static DFT calculations and classical MD simulations using these force fields showed that adsorbed CDB molecules are mobile at room temperature and stabilized at step edges due to increased adsorption energy. These results provide insight into the processes and mechanisms that govern deposition, adsorption, and diffusion of atoms and molecules on insulating surfaces and can help guide the design of functional molecules and films.

Much of the recent work on optically tunable methods have relied on the use of optically tunable switches. Although these methods provide effective tuning of microwave devices particularly in the lower microwave band, there is the fundamental limitation that the position of the switch is always fixed which limits the capability for tuning. Several previous investigations have looked at using spatial variations in the illumination pattern. These have always required the use of high power bulky laser sources which cannot be integrated into the microwave device. The recent advances in semiconductor laser technology allow both intensity and spatial profiles of illumination to be varied dynamically at speeds of up to fractions of a microsecond while maintaining a compact form factor. This opens up a new area for investigation in optically tunable microwave devices which provides the motivation for the current work. The primary focus of the project is to investigate new designs of optically tunable microwave circuits arid antennas that can take advantage of the spatial and intensity variations of the illumination profile and at the same time maintain a small form factor. In order to achieve this a significant portion of work was required to characterize the loss mechanisms taking place inside the optically illuminated region at high frequencies. This material is presented and is followed by investigations into new types of tunable microwave devices. The significant contributions of this work are contained in Chapters 4,5, and 6. The characterization of optically illuminated plasmas presented in current literature is limited to small regions of illumination. Chapter 4 extends this microwave characterization to longer lengths of illumination and also to higher microwave frequencies. The first part of Chapter 5 presents new techniques for tunable loads based on illumination pattern variations. The second part presents a novel technique for producing variable true time delay phase shifts which has not been demonstrated previously. Chapter 6 shows several new methods for designing tuneable microwave antennas based on integrating light sources within the microwave structure. This work has contributed to expanding the current literature on optically tunable devices. The fundamental focus has been on the use of miniature light sources since these can be integrated into the structure of the microwave device to form a compact tunable package. Several new ideas have been presented based on this concept.

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In this PhD thesis the development of laser-based processes for packaging applications in microsystems technologies is investigated. Packaging is one of the major challenges in the fabrication of micro-electro-mechanical systems (MEMS) and other micro-devices. A range of bonding processes have become established in industry, however, in many or even most cases heating of the entire package to the bonding temperature is required to effect efficient and reliable bonding. The high process temperatures of up to 1100°C involved severely limit the application areas of these techniques for packaging of temperature sensitive materials. As an alternative production method, two localised heating processes using a laser were developed where also the heat is restricted to the joining area only by active cooling. Silicon to glass joining with a Benzocyclobutene adhesive layer was demonstrated which is a typical MEMS application. In this laser-based process the temperature in the centre of the device was kept at least 120°C lower than in the bonding area. For chip-level packaging shear forces as high as 290 N were achieved which is comparable and some cases even higher than results obtained using conventional bonding techniques. Furthermore, a considerable reduction of the bonding time from typically 20 minutes down to 8 s was achieved. A further development of this process to wafer-level packaging was demonstrated. For a simplified pattern of 5 samples the same quality of the seal could be achieved as for chip-level packaging. Packaging of a more densely packed pattern of 9 was also investigated. Successful sealing of all nine samples on the same wafer was demonstrated proving the feasibility of wafer-level packaging using this localised heating bonding process. The development of full hermetic glass frit packaging processes of Leadless Chip Carrier (LCC) devices in both air and vacuum is presented. In these laser-based processes the temperature in the centre of the device was kept at least 230°C below the temperature in the joining region (375°C to 440°C). Testing according to MIL-STD-883G showed that hermetic seals were achieved in high yield processes (>90%) and the packages did withstand shear forces in excess of 1 kN. Residual gas analysis has shown that a moderate vacuum of around 5 mbar was achieved inside the vacuum packaged LCC devices. A localised heating glass frit packaging process was developed without any negative effect of the thermal management on the quality of the seal.

This thesis investigates the piezoelectric thin film actuation of RF MEMS devices. lt is demonstrated that piezoelectric actuation using silicon structures with integrated PZT thin film is suitable for RF MEMS switches and mechanical filters. Both these devices are studied, fabricated and tested. To assist the mechanical design of a piezoelectric microswitch an electrical model is developed, from which design parameters can be derived to meet the requirement of an insertion loss of -1dB and an isolation loss of -40dB at 4GHz. The model shows how the switching gap and the overlapping dimension are two key parameters and the ratio between the two should be larger than 0.15. Switching gaps are chosen as 5m and 7.5m from the designed range of 3 ~ 15m. An equivalent circuit network incorporating a transmission line model of the coupling beam is developed to demonstrate a design method for the mechanical filter. The model reveals that the coupling beam stiffness, coupling position, electromechanical coupling factor and the quality factor of the piezoelectric cantilever have substantial effects on filter characteristics. A narrower/wider bandwidth with higher/lower filter Q can result if the coupling position is near/further to a cantilever's anchor position. Extreme situations of the above two coupling cases result in filter bandwidth's disappearing and filter centre frequency's shifting. For a desired filter insertion loss source and load resistances need to be determined by quality factors of terminal circuit and coupled resonators. A bulk micromachining process compatible with the integration of PZT thin film onto silicon is developed. ln general, for PZT pattern size above 100m wet etching could give satisfactory pattern definition, however for pattern size below 50m dry etching is needed. To etch a thickness 2 1m PZT film long dry etching lime demands for the survivability of a masking material. ln this study a technique combined of dry and wet etching is developed for a 1m PZT film. lt is found that a low pressure promotes a higher etch rate and the best etching conditions are a gas mixture with a composition of 1/4 for CHF3/Ar at a total gas flow of 25sccm under a RF power of 150W. Dry etching is also developed to release cantilevers from the buried S102 layer with conditions of a gas mixture of 13sccm CHF3 and 3sccm 02 at 80mTorr and a RF power of 100W in 30mins for 1m Si02. To be compatible with PZT elements silicon cantilevers are processed using deep reactive ion etching. PZT thin film actuation has been demonstrated successfully with PZI' thin film integrated silicon cantilevers. A static deflection of 2.89m is measured at an actuating voltage of 20V for a 100m wide and 450m long cantilever. A displacement of 556nm at 12.98 kHz resonance is measured for a 200m wide and 850m long cantilever under a 10mV AC plus a 10V DC. A piezoelectric strain constant d31 of 30.15pC/N has been obtained for the PZT thin film used in this study. Filter resonant modes and impedance responses are measured. The filter concept design is justified by the obtained results. Using the impedance data the electromechanical coupling factor, filter centre frequency, filter bandwidth and filter Q are determined. There is a good agreement between the measured and calculated filter centre frequencies. At the first filter resonant mode a maximum piezoelectric coupling factor of 0.19 and a maximum resonator-Q of 235 are recorded. At the second filter resonant mode a maximum of 0.12 and a maximum resonator-Q of 360 are obtained. Results show smaller coupling factors than required at the 13' and 2" centre frequencies for all measured filters. This implies that pass bands of designed filters will be missing from their responses at the 18' and 2" centre frequencies. Design improvements are given in the relevant results discussions. Residual stresses are studied for deflected cantilevers after release. The tensile stress of PZT, the converted tensile stress of Pt and the compressive stress of remaining buried SiO2 layer could result in the upwards-deflected cantilevers. The compressive stress of P could compensate the tensile stress of PZT and flatten the cantilever beam. lf the buried SiO2 layer is removed incompletely or if the tensile stress of PZT layer is very high, then upwards-deflected cantilevers would result. Measurements of the most switch cantilevers show larger initial deflections than the designed switching gaps. Finally, conclusions and suggestions of future work are given.

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