Thesis (Ph. D.)--University of Wisconsin--Madison, 1983. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 401-411).

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Chicago, 1920. / "Private edition, distributed by the University of Chicago libraries, Chicago, Illinois." "Reprinted from the Physical review, n.s., vol.xviii, no. 6, December, 1921." Also available on the Internet.

Thesis (Ph. D.)--University of Chicago, 1915. / "Reprinted from the Physical review, n.s., vol. III, no. 5, May, 1914." Includes bibliographical references. Also available on the Internet.

Physical vapour deposition technologies have been on the fast track of development for the last two decades due to their ability to meet demands for special materials and performance tools. The ever increasing complexity of the required coating microstructure and chemical composition can be achieved only by the development of PVD technology and in particular plasma sources for vapour generation that can provide the necessary tools. This thesis describes plasma diagnostic studies of plasma discharges, developments of plasma sources and deposition of CrN coatings. Initially the project investigated vacuum arc plasma discharges used in the Hauzer HTC1000/ABS industrially sized coater. The attention was concentrated to the plasma pretreatment by low energy (1200 - 3600 eV) Cr ion implantation into substrates, which contributed to an enhanced adhesion of subsequently deposited TiAIN coatings. Optical emission spectroscopy (OES), electrostatic probes, and time-of-flight (TOF) spectroscopy were used to study the interactions of the arc plasma with the gas atmosphere in the chamber. It was shown that increasing the pressure of Ar gas had a strong effect on the composition of the generated metal ion flux as the density of highly charged metal species reduced significantly to the benefit of gas ionisation. The mechanisms behind these observations are discussed and supported by further experiments. Based on the plasma diagnostic results, a novel two-stage pretreatment method was developed which allowed an enhanced adhesion due to faster sputter cleaning of the substrate surface and more efficient metal ion incorporation in the substrate material. In the final stages of the project a novel high power pulsed magnetron sputtering (HIPIMS) process utilising peak power densities of 3000 Wcm[-2] was investigated. OES studies showed the first evidence of doubly charged Cr and Ti ions generated by the HIPIMS discharge. Peak plasma densities of 10[13] cm[-3] were measured and, in the case of Cr, metal ions were found to constitute 30% of the total deposition flux to substrates. The influence of power on the plasma density, plasma composition and time evolution of the plasma was studied in detail using OES and electrostatic probes. The conditions for glow-to-arc transition were investigated. CrN coatings (thickness 2 mum) were deposited for the first time using HIPIMS of Cr in a nitrogen atmosphere. The microstructure observed in transmission electron microscopy cross sections was highly dense and droplet free and contributed to an excellent corrosion and wear resistance superior to 20 mum thick electroplated hard Cr, and CrN coatings deposited by arc and unbalanced magnetron sputtering. The HIPIMS discharge was used also for pretreatment of substrates with metal ions analogous to the one performed previously with arc discharge. High adhesion was achieved as indicated by the scratch test critical load value Lc = 85 N.Finally, at an intermediate stage of the PhD project, an alternative source providing metal ionisation was studied. It was based on a radio frequency (RF) powered coil that was inductively coupled to a magnetron sputtering discharge. Energy resolved mass spectroscopy and OES in a laboratory-sized version of the plasma source revealed elevated metal ion densities and high ion energies of the order of 60 eV. This source was upscaled, installed, and tested successfully in the industrially sized Hauzer coater. The ion-to-neutral ratio at the substrate position could be increased 5-fold for a similar increase in RF power.

[No abstract available] / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A high-frequency discharge ion source was developed yielding 45% protons in an 800 microampere, 14 kv energy focused beam of positive hydrogen ions. Higher ion currents could be delivered at higher voltages. The discharge was excited in a pyrex discharge tube, 1¼ inches in diameter and 9 inches long, by a 210 Mc/sec. push-pull, oscillator capable of delivering 120 watts power. An electrostatic potential difference of 1.8 kv applied axially with the discharge tube, accelerated the positive ions formed in the discharge toward the exit canal. A magnetic field of 240 gauss, also applied axially, shaped the discharge conically, and intensified the redness of the discharge, causing the Balmer lines to appear prominently when the discharge was viewed through a spectroscope. The ions emerging from the exit canal were focused by an electrostatic lens using a potential difference of 12 kv. The hydrogen pressure in the discharge tube measured 17 microns, and the rate of hydrogen consumption measured 11 cc. per hr. The proton percentage was found to depend on the oscillator power and critically on the gas pressure. The magnetic field increased the proton percentage, but in an unpredictable manner. It was also found that the focusing lens in front of the probe canal exerted an extracting action on the ions in the discharge; influencing very strongly the total ion beam current collected. The general performance of the ion source was found to be satisfactory. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Reignition curves have been obtained for a high current (40ka) spark gap channel in air at atmospheric pressure at various radial distances down to delay times of 50 µs. after initiation of spark. The reignition curves in the ‘thermal breakdown' regime are obtained by a constant voltage generator having a variable output ranging from 100 volts to 2.5 kv, while those in the 'spark breakdown' regime are obtained by the use of a restriking voltage generator having a higher voltage output ranging from 1 kv to 15 kv. The experimental results show that the gas at large radial distances recovers faster than that at a smaller distance. A special feature of the recovery curves is the occurrence of a dip which is thought to be the effect of a thermal wave. Gas temperatures are derived by using the equation of state, Paschen curves and the reignition measurements. A temperature profile of the spark channel has been obtained which indicates that the spark channel has a fairly uniform temperature up to a radial distance of 2.5 cm. Beyond this distance the temperature drops rapidly to ambient temperature at a radial distance of 4 cm, Deionization and recovery mechanisms are predicted theoretically and are verified during the earlier recovery period in which 'thermal breakdown' occurs and during the later recovery period when 'spark breakdown' is observed. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The glow phase of high pressure spark discharges initiated by the Townsend mechanism of breakdown in hydrogen, nitrogen and carbon dioxide is studied using 16 ohm coaxial cable discharge techniques. Before the establishment of the spark channel in these low over-voltaged spark discharges, there exist two distinct transition stages, namely, a diffuse glow phase and a filamentary glow-to-channel transition phase. The optical appearance of the diffuse glow is similar to that of a normal d.c. glow discharge. It consists of a negative glow, a Faraday dark space, and a positive column. From our experimental results it is concluded that for the glow phase the cathode fall voltage and the ratio of the axial potential gradient to the gas pressure in the positive column are fixed for each gas. These values are independent of the impedance of the external circuit and the gas pressure. Comparisons with low pressure d.c. glow discharges indicate further that the cathode fall voltages are in agreement in both types of glow for the gases' investigated. In addition, a qualitative discussion about the transition nature of this diffuse glow phase is given on the basis of results obtained from spectroscopic investigations. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Spectroscopic investigations have been carried out on hollow cathode discharges adapted from laser technology for use as a spectroscopic light source and the argon inductively coupled plasma (ICP) as an excitation source for nonmetal emission. High and low voltage aluminum and copper hollow cathode discharges were studied as a source of ionic and resonant atomic metal emission. The high voltage versions achieve strongly positive current-voltage behavior through utilization of the obstructed discharge phenomenon. The current-pressure-intensity-voltage relationships for low and high voltage copper hollow cathode discharges were studied with the inert gases He, Ne, Ar, Kr, and Xe. The intensity for copper resonant atomic emission with the fill gases Ar, Kr, and Xe improved relative to neon in the high voltage lamp when compared to the low voltage lamp. Absorption measurements through the cathode bore show the ground state atom density to increase with the atomic weight of the fill gas at any given level of intensity, at the fill gas pressure yielding highest resonant atomic copper emission. The estimated ion/atom intensity ratio is increased with fill gases which have metastable or ionization energies greater than the excitation energy of the ion transition. A copper hollow cathode lamp incorporating a short positive column discharge in front of the cathode opening was investigated for its lineshape as measured spectroscopically and by its atomic absorption sensitivity. Incorporation of this positive column allowed higher intensities to be obtained at the same line quality as a commercial hollow cathode lamp. An enlarged cathode volume also improves the lineshape at a given intensity. Inductively coupled plasma spectra for the elements C, O, N, Cl, P, S, and Br were obtained in the vacuum ultraviolet utilizing a vacuum polychromator and SWR film. The detection limit for injected O₂ and N₂ detected electronically by the VUV emissions is 1.3 and 0.9 micrograms respectively with this system. A VUV filter photometer was utilized for oxygen and phosphorus analysis. The detection limit for injected oxygen was 1 microgram with this photometer; the detection limit for phosphorus as inorganic phosphate in aqueous solution is 10⁻³ M. The bandpass of the photometer limits its selectivity.