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No description available.

No description available.

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The aim of this research is to better understand the behaviour of pulsed discharges and electron dynamics for the purpose of tailoring the plasma properties for neutral beam etching (NBE) applications. A capacitively coupled plasma formed in a research system was used for a study of pulsed tailoring in an electropositive plasma. A combination of high time resolved optical diagnostics, plasma imaging and optical emission spectroscopy, and hairpin probe measurements were used to study the electron density and the energy distribution function during the ignition phase of a repetitively pulsed plasma. Two different waveforms were used to modulate the envelope of the input RF -voltages in order to control the ignition phase, by changing the increase rate of the electron density and evolution of the electron energy distribution function (EEDF). The results of this study indicate that the increase rate of the electron density and the EEDF, during operation, can be influenced and even controlled to some extent by pulse tailoring. Electron densities of the order of 1016 m- 3 were obtained, and EEDFs of a highly non-:'1axwellian nature were characterised during the ignition phase. Also, the ignition timescales were controlled by applying pulse tailoring from a few microseconds (typically 2 μs) to a few tens of microseconds (80 μs) for the different input waveforms. An inductively coupled plasma in an industrial plasma etching tool was used to study pulse tailoring in electropositive and electronegative discharges. The same environment was used to create a source to from energetic negative ions which could then be extracted and neutralised. Similar diagnostic techniques, as those used in the research source, in addition to RF-probes were used to characterise the inductive source. Optical emission spectrascopy and electron density measurements showed. that the plasmas, almost instantaneously, ignite in the H-mode. The EEDFs were characterised by a Maxwellian distribution with an electron temperature ranging between 1.2 up to 1.6 eV, and electron densities of the order 1018 m- 3 were measured, depending on the operating conditions. This source was also used for preliminary NBE studies. Neutralisation efficiencies ranging between 70% and 95% were measured, and etch rates of 25 and 30 nm/ min were found

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This work considers the model problem of wave transmission along a fluid-loaded plane membrane supported by a finite number of equally spaced ribs with dynamic constraints. One of the ribs is driven by a prescribed time-harmonic line force applied uniformly along its length and the remaining ribs are passive. The steady-state, time-harmonic response of the ribs is investigated with particular emphasis on whether the disturbance is localized near the driving force and if so, at what rate the disturbance decays. Under the assumption of subsonic surface wave coupling only, which is explained in the text, closed-form solutions for the rib-forces are first obtained. The system is shown to exhibit a stop/pass band structure characteristic of one-dimensional periodic systems with lossless coupling between adjacent bays. The drive frequencies which define the band edges are ascertained and their dependence on the properties of the passive ribs is illustrated in detail. A critical rib mass is found at which the disturbances at the ribs vanish. The properties of the previously neglected acoustic (or hydrodynamic) coupling are then studied in order to determine the conditions under which the surface wave coupling approximation is appropriate. Some stop band solutions which include both surface wave and acoustic coupling are found which indicate the relative importance of the two types of coupling. Much of the analytical work is confirmed by numerical results and the methods used to derive these are explained.

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