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In this dissertation we will investigate the possibility of the Coherent Control of Surface Plasmons. Such Coherent Control will be defined as the ability to excite particular Surface Plasmon spectral components using a femtosecond laser pulse and to control their removal and enhancement using a second pulse, as a function of the temporal separation of this second pulse from the first. A number of different possible device structures, materials and laser sources are investigated theoretically and experimentally. This leads to a demonstration of the removal of Surface Plasmon spectral components of our choice in a Surface Plasmon wave-guide by varying the time separation of exciting double-pulses from an actively stabilised Mach-Zehnder interferometer. We have termed such a mechanism <i>propagating </i>Coherent Control as a result of the travelling wave nature of the Surface Plasmon excitations. This work is supported by theoretical models of decay processes and coupling efficiency which match successfully with experiment. An analysis implying significantly lower dispersion for Surface Plasmons propagating in the structures fabricated than for light travelling in silica is performed. In addition, we investigate in detail the possibility of the <i>static </i>Coherent Control of Surface Plasmons, that is, Coherent Control at the point of excitation. Computer models of device structures, experimental control and measurement of excitation bandwidths and experimental attempts at Coherent Control allow us to place limits on the possibilities of success in this area. We conclude that additional fabrication outside the scope of this project is required for this form of Surface Plasmon Coherent Control; a route is detailed.

The first section of this dissertation is directed towards understanding the chemistry of free radicals and other discharge products in low pressure methane and mixed methane plasmas. The behaviour of the discharge products in a 10 kHz parallel plate reactor was investigated through IR diode laser absorption spectroscopy of their rovibrational lines. The behaviour of the methyl radical, CH<SUB>3</SUB> in pure methane plasmas has been reinvestigated and extended and kinetic data relating to some electron impact dissociation reactions have been estimated. Methyl radical concentrations in very dilute methane in hydrogen mixtures (about 1%) have been measured for the first time. Nitrogen dioxide was shown to be a much more efficient scavenger in the plasma than nitric oxide. It was also shown that the CH<SUB>3</SUB> concentration in the plasma did actually increase when oxygen was added in small amounts. The presence of many other species such as C<SUB>2</SUB>H<SUB>2</SUB>, C<SUB>2</SUB>H<SUB>4</SUB>, C<SUB>2</SUB>H<SUB>6</SUB>, CH<SUB>2</SUB>O, CH<SUB>3</SUB>OH, HCOOH, CO and CO<SUB>2</SUB> in CH<SUB>4</SUB>/H<SUB>2</SUB>/O<SUB>2</SUB> plasmas have been confirmed and their concentrations measured. A chemical model to simulate these plasmas has been written using a modelling package called FACSIMILE. Good agreement was found between measured and calculated concentrations for most of the species detected. The second section of the dissertation concerns velocity modulation IR spectroscopy of diatomic ions in plasmas. High-J pure rotational lines belonging to HeD<SUP>+</SUP> have been observed using an air cooled ac discharge in helium and deuterium. Thirteen lines in the v=0 and v=1 states between 620 and 720 cm<SUP>-1</SUP> were measured including a bound-to-quasibound transition of HeD<SUP>+</SUP>. A least squares fit using both observed and the previously reported lines has given much more accurate constants than earlier work. The IR absorption spectrum of SiCl<SUP>+</SUP> has also been investigated and this ion was generated in a discharge of SiCl<SUB>4</SUB> and He. About 180 lines were observed in the region between 620 and 700 cm<SUP>-1</SUP> and assigned to the fundamental and hots bands of <SUP>28</SUP>Si<SUP>35</SUP>Cl<SUP>+</SUP> and its isotopes. A least squares fit of these lines yielded nine mass-independent Dunham coefficients for SiCl<SUP>+</SUP>. A potential energy curve for the electronic ground state of SiCl<SUP>+</SUP> has been derived and the dissociation energy for the lowest channel i.e. SiCl<SUP>+</SUP> and Si<SUP>+</SUP> has been determined for the first time.

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Electron Microscopy and Electron Beam Lithography Systems are widely used in industry and research. The ultimate performance of such systems is determined by the brightness of the source from which the electrons are derived, a higher brightness allowing greater resolution at a given probe current. In addition to brightness, lithographic systems frequently require high absolute current. This dissertation addresses theoretically and experimentally the formation and characteristics of electron beams with a brightness of 10<SUP>6</SUP>A/cm<SUP>2</SUP>-sr or more using limited-area thermionic sources. The various emission mechanisms used in electron guns are described and the brightness of an electron source is discussed. Space charge limits the available current density in the gun region and the focused current in the drift space of an electron beam analyser. Two models for predicting the performance of limited-area-cathode guns are proposed and agree well with the experimental results. Taguchi's methodology is introduced to undertake a systematic optimal design of an electron gun using an electron optical program, the 'Source' program. The experimental and theoretical results indicate that the major limitation to the performance of limited-area-cathode guns lies in the gun structure, especially, the emitting radius of the cathode and the manner of cathode emission itself rather than the drift-space. A new gun structure will be required if a brightness of 10<SUP>8</SUP>Amp/cm<SUP>2</SUP>-sr at 30 kV (or an equivalent figure at lower voltages) is to be achieved. On the other hand, the analysing section can be modified so that such a brightness value can be measured.

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No description available.

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