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Many methods are currently used for the production of silicon oxide films, most have drawbacks associated with high temperatures and the requirement for a vacuum. Atmospheric pressure plasma treatment can address some of these difficulties. Air silent discharge treatment of spin-coated organo-silicon compounds resulted in substantial oxidation. The depth and morphology of the oxidised region was found to depend on the structure of the precursor. Condensation of substituted chlorodisilanes (SCDS) onto polymer surfaces yielded polysiloxane-like layers. Upon atmospheric pressure plasma oxidation these gave rise to SiOx rich films which exhibited gas barrier, and readily underwent reaction with conventional chlorosilane coupling reagents. Dielectric barrier discharge and atmospheric pressure glow discharge (APGD) modification of polydimethylsiloxane (PDMS) containing polyethylene blends led to the formation of wettable, SiOx rich coatings. The hydrophobic recovery, SiOx content, reactivity and topography of the oxidised films was found to depend on the architecture of the PDMS additive. The limited depth penetration of plasma oxidation was thought to limit its potential as a gas barrier technology. The development of a novel APGD plasma reactor equipped with an ultrasonic nozzle enabled the creation of thick coatings from cyclotetrasiloxane monomers. Control of the feed gas allowed the rapid deposition of both hydrophobic polysiloxane-like films and hydrophilic SiOx gas barrier coatings. The APGD deposition methodology was extended to the creation of organic plasma polymers. The resultant polyacrylic acid and 1H, 1H, 2H,- perfluoro-1-octene films were highly functionalised and exhibited properties comparable with their conventionally manufactured counterparts.

This thesis presents the development of novel stretchable conductors based on gold films magnetron sputtered on polydimethylsiloxane (PDMS). The Thesis starts with an overview of the available state of the art in stretchable conductors and their applications in smart fabrics, biomedicine and consumer goods. It then identifies two novel methods designed to improve these conductors using a/ hydrogenated amorphous carbon (a-C:H) interlayers and b/ carbon nanotube CNT/PDMS composite substrates. The ultra-thin thin a-C:H films were deposited on PDMS by Plasma enhanced chemical vapour deposition (PECVD). Atomic force microscopy (AFM) showed that the a-C:H film buckled, resulting in a linear surface length increase of 6-6.5%, potentially very useful to relieve tensile strains. Electro mechanical tensile cycling measurements showed a 280 fold decrease in electrical resistivity for the gold conductor with a-C:H interlayer when compared to that without interlayer. The electrical resistivity obtained with a-C:H interlayer, 8xlO-6 O.cm, was smaller than the best published v.lues to date (-3x!O"' D.cm). After tensile cycling both samples return to their original position but leaving remarkable differences in their electrical resistance, - 9 0 for the sample with a-C:H interlayer but -3000 n for that without a-C:H interlayers. The SEM micrographs also shows much improvement in terms of crack density and delaminated area for the gold conductor with a-C:H interlayer. Angle resolved XPS and SIMS analysis indicate that the a-C:H is intermixed with the PDMS substrate resulting in a graded interface, because of the energetic carbon ions used in the PECVD process. Hence, the beneficial effect of the a-C:H interlayer is two-fold; it forms a graded layer, which reduces the thermal strain mismatch and it produces an increase in specific surface area which reduces the applied biaxial tensile stress. This latter effect was confirmed by Finite Element Analysis (FEA) of the buckled a-C:H surfaces using the acquired AFM images to define the modelling geometry. The second part of the thesis examines gold coated CNTIPDMS conductors. These composite substrates were prepared by in situ curing. UV -Visible absorbance and Raman measurements showed that sonication treatments can lead to the breakage of tubes but are also efficient in dispersing the tubes within the polymer. Raman analysis of the composites shows that there is an intercalation and chemical reaction that restrict the vibration of CNT characteristic peaks and this leads to higher Raman ID/IG ratio, i.e. more defects in the CNT, reduces the electrical resistivity and lowers the mechanical properties. At rest, the conduction in the gold coated samples depends on the conduction in the composite substrate but also on the crack pattern in the gold layer. As the cracking results from a thermo-mechanical mismatch, it is sometimes more severe for the gold layers deposited on composite substrates. Cyclic tensile testing however shows that the gold layers deposited on composite substrates perfonn better in leon of conduction under load and fatigue resistance. To conclude, this project showed that, while both of these innovative approaches perfooned well, they gave complementary results; the a-C :H interlayer mainly reduce the zero strain resistivity of the conductors while the CNT composite substrate assisted the conduction under loading conditions.

The meatgrinder is a high-efficiency inductive energy storage and transfer circuit which may be used to supply high-current pulsed power requirements in applications such as electromagnetic propulsion. It overcomes the inherent 25% efficiency limit when transferring energy between uncoupled inductors and simultaneously provides current multiplication. An unloaded six-step demonstration circuit has been used to multiply current from 7A to 76A at an efficiency of 44%, and a single-step demonstration circuit has been used to multiply the current in an uncoupled load induct or from lOA to 30A, the efficiency of energy transfer being 31%. Both circuits use power MOSFETs for switching. These circuits have been used in conjunction with theoretical analysis and computer simulation to study the design and performance of the meatgrinder. Investigations have been carried out in order to confirm the basic theory, to clarify the details of circuit operation, and to provide the information necessary for future feasibility studies.

The characteristics and theories of four-layer pnpn semiconductor devices have been considered with particular reference to the two transistor analogy of thyristor in order to obtain an expression for the current-voltage characteristics of the device. The Small-signal, low-frequency current gains of the npn and pnp transistor sections of high and low power thyristors were measured by a three terminal method originally employed by W. Fulop. The technique is shown to be applicable to measurements on high power thyristors. The current gains of two transistor component were also measured as a function of temperature at a series of anode currents. From this it can be shown that the temperature dependence of two-terminal latching current can be qualitatively estimated from the plot of current gain measured at a series of temperature for constant anode current. Analysis of instability of devices with temperature showed that-, the saturation current-of isolated centre junction plays a dominant role. Gold doping predictably leads to low current gain of the pnp transistor section. Current gain measurements of thyristors with and without shorting dot showed an. almost similar variation with frequency. For both type of devices αnpn0 was almost equal and even closer at high temperature (1000C). The theory of the influence of shorting dots on current flow in thyristors outlined in a report by W. Fulop, was developed. The value of IL’ hole lateral current in the p-base is found and its dependence upon p-base width and shorting dot area investigated. The voltage distribution in the two central base regions just after the device has switched on but before the plasma has had time to spread is investigated. It was found that junctions J1 and J2 become reverse biased and share the bias reverse voltage. Calculations shows that for very large V OFF' the voltages in these two junctions are equal. In order to have a better understanding of thyristor behaviour, the set of one-dimensional non-linear partial differential equations describing the Poisson's equation and the two current continuity equations are solved numerically under steady-state conditions. The potential distribution and the hole and electron current density distribution within the device plotted one-dimensionally are given.