Donald E. Horne

The chemisorption of nitrogen at activated sites on a polycrystalline tungsten surface

Abstract The exposure of a polycrystalline tungsten surface to atomic nitrogen or bombardment by N 2 + is shown to enhance chemisorption. Ion bombardment causes the saturation coverage to be increased by about 50 % over that found after exposure to the molecular gas. A somewhat greater saturation coverage is obtained by exposure to neutral atomic nitrogen. The additional gas found in these experiments is desorbed at lower temperatures than nitrogen chemisorbed in β sites. These results are interpreted on the basis of chemisorption at endothermic adsorption sites.

Experimental approaches for assessing interfacial behavior of polymer films during dissolution in aqueous base

We describe here experiments aimed at probing the interfacial behavior of thin polymer films during dissolution. We have constructed and characterized a unique quartz-crystal microbalance dissolution rate monitor that allows changes in both oscillation frequency and resistance to be accurately recorded at high data rates during film dissolution. Depending on polymer structure and properties, the resistance to be accurately recorded at high data rates during film dissolution. Depending on polymer structure and properties, the resistance can remain nearly constant, or can undergo enormous fluctuations that are indicative of transient changes in mechanical properties of the polymer layer during the dissolution process. A theoretical description allows the measured resistance to be related to the structure and properties of the dissolving film. This QCM apparatus has been coupled with a custom high-speed visible reflectance spectrometer, and with an infrared spectrometer, to provide information on the structure of the dissolving film and its chemical composition. The dissolution and swelling of well-defined acrylic and alicyclic copolymers in aqueous base has been examined using these techniques.

Dummy load technique for power efficiency estimation in rf discharges

We have developed a simulated load technique for estimating power dissipation and effective impedance of the discharge which is useful over a wide range of driver frequencies. This is used to calculate the power delivered to the plasma and plasma current for frequencies from 0.12 to 13.56 MHz. This technique allows an efficiency calibration curve to be made for a given match circuit which can be quickly applied to any new discharge condition to give match efficiency.

Modified Magneto‐Optic Hysteresigraph

A previously described apparatus for the direct recording of Faraday rotation and magnetic hysteresis has been modified to improve the magneto‐optic rotation sensitivity by about a factor of 10 compared with the original equipment. Kerr and in‐plane Faraday rotation capability has been added and the maximum available field strength has been doubled.

High Voltage Sweep and Controlled Magnetic Lens Current Supplies for the Electron Microprobe

Three electronic systems have been developed for the electron probe x‐ray microanalyzer to provide (1) automatic sweep of the electron beam high voltage, (2) automatic control of the target current as the electron beam voltage is varied, and (3) automatic control of the electron beam focus as the beam voltage is varied. In addition to conventional applications in quantitative electron probe microanalysis, special applications of these components include measurement of absorption coefficients for soft x rays, voltage dependence of cathodoluminescence in semi‐conductors and insulators, three dimensional microanalysis, and ditital computer control of the microprobe analyzer.