No description available.

No description available.

Abstrate Co1-XO polycrystals, prepared by sintering at 1600oC with or without Mg2+-dopant ,were thermally etched at 400-1500oC for 10 min-12hr and studied by scanning electron microscopy regard to the effects of temperature and Mg2+-dopant on etching development. In low etching temperature (400-800 oC), vacancy relaxation process and spinel precipitate produced on the surface of Co1-XO-MgO polycrystals. In high etching temperature (1500 oC), Co1-XO epitaxy was spread on the steps and ledges. In addition, Co1-XO was thermally etched at 1500 oC for 10min to 12hr, we found triangular to hexagonal etch pits were produced. However, Mg2+-dopant changed the geometric shape of the pit opening. Besides, growth hillocks with corrugated terrace steps at edge and a pit at center showed that growth and etching of crystal can happen in the same time.

No description available.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Abstract The objectives of this thesis are to investigate the microstructures and the corrosion resistance of chromium (Cr) and nichrome (Ni-Cr) thin films deposited by rf magnetron sputtering. Different rf powers were used to prepare the Cr thin films on glass substrates. The thin films were then patterned and subsequently annealed in vacuum environment. The targets used for the sputtering are commercially available Cr and nichrome with 4N and 99.95% purity, respectively. Two different nichrome targets were used. The composition of Ni in nichrome are 40 and 80%. The sputtered samples were etched by reactive ion etching in a mixture of SF6 and O2 for testing the corrosion resistance of the deposited films. The thin films with excellent surface morphology and corrosion resistance can be obtained by preparing the films at a low rf power. This is because the films had lower stress and less defects than the films prepared by high rf powers. At a low power of 20W, the etching rates as low as 120Å/min and 50 Å/min for Cr and nichrome were achieved. The annealing effect of the deposited films at different temperature are also discussed.

No description available.

No description available.

Plasma etching, the selective removal of materials by reaction with chemically active species formed in a glow-discharge, is widely used by the electronics industry because of the advantages over 'wet' processes. The full potential has yet to be realised because chemical processes occuring in the plasma and at the plasma/substrate interface are incompletely understood. In this work attention was focussed on the accumulation of polymers on surfaces during plasma etching in fluorocarbon gases. An apparatus was designed and constructed to explore the conditions which give rise to these deposits by: i) The detection of the excited species such as CF and CF₂ (by optical emission spectroscopy); and ii) The rate of accumulation or removal of deposits (by means of a quartz crystal microbalance). The gases CF₄, C₂F₆, C₃F₈ and CHF₃ were used at pressures between 200-600mT, together with mixtures with H₂ and a few runs with other gases to vary the partial pressures of etching and polymerizing species. Both substrate effect of, viz silicon and thermally oxidised silicon (SiO₂), and electrode materials effects have been examined. Polymer production from C₃F₈ has been found to be more sensitive to electrode composition than that from CHF₃, but the material formed is overall less thermally stable. On the other hand, polymers produced from C₃F₈ accumulate at similar rates on Si and SiO₂, whereas those from CHF3 show a much greater liklihood of building up on Si than SiO2 . XPS and infra-red spectroscopy have been used to demonstrate that polymers arising from these two gases exhibit marked structural differences, which can be minimised by mixing H₂ with C₃F₈. These effects can be correlated with the decomposition products expected in the plasma.

Optical diagnostic techniques have been developed and then used to investigate the chemistry of reactive species formed in CF₄ / O₂ rf parallel plate discharges, similar to those employed in semiconductor material processing. Oxygen atoms were detected by two photon laser induced fluorescence (LIF), and the technique was found to have a number of experimental caveats owing mainly to the high laser intensities required. In particular, amplified spontaneous emission (ASE), was observed from laser excitation of oxygen, and was found to influence the spontaneous fluorescence signal and thus question the use of LIF for ground state concentration measurements in these systems. The spin orbit states of the 3p ³P level were resolved for the first time, both in using high resolution excitation experiments and also as a consequence of detecting ASE. Spin orbit temperatures of less than 50° above ambient were observed. The absolute concentration of oxygen has been found to be 7.4 ± 1.4 x 10¹³ cm^-3 in a 50 mTorr, 100 W, 85% O₂ / CF₄ plasma. Optical emission was also used to study fluorine atoms and to examine the use of the actinometered emission technique as a measure of ground state concentrations. The latter was investigated directly by comparison with LIF measurements of O and CF₂, and in many cases shown to be a poor representation of the ground state concentration. To investigate the chemical and physical processes in the plasma, time resolved methods are required and a new technique, time resolved actinometry, has been developed, tested by comparison with LIF measurements and then used to study the kinetics of fluorine atoms. Results have shown the importance of wall reaction rates on the magnitude of the fluorine atom concentrations, and the sensitivity of these concentrations to the nature of the surface, particularly in the presence of oxygen and silicon. Oxygen has also been shown to be removed predominantly at the surface but the influence of gas phase reactions with CF_x radicals is apparent in discharges containing low percentages of O₂. Studies on an afterglow type, electron cyclotron resonance reactor have been carried out as a comparison to the parallel plate system, and high excitation and dissociation levels have been observed from differences in the emission intensities and from measured values of the absolute CF and CF₂ concentrations. The use of LIF as a diagnostic for CF has been investigated by probing the predissociation of the A²Σ⁺ state. Emission from the A²Σ⁺ (v = 2) level has been seen for the first time, and a J independent predissociation mechanism, with a rate of 3 x 10⁹ s^-1 has been observed.