Volume 89, Issue 12, 15 June 2001
Index of content:
- PLASMAS AND ELECTRICAL DISCHARGES (PACS 51-52)
89(2001); http://dx.doi.org/10.1063/1.1371940View Description Hide Description
We present a simple technique for determining the absolute fluorine atom concentration in pure capacitively coupled radio-frequency discharges. It is based on the measurement, by laser-induced fluorescence, of the loss rate of the radical in the afterglow of a pulsed plasma. We first demonstrate that in our conditions, is lost only by gas phase recombination with F atoms (with a known rate constant and by recombination at the reactor walls at a rate independent of the rf power injected. Hence, the total loss rate, varies linearly with [F] when the rf power is increased. By recording and the relative variation of the F atom concentration (by optical emission actinometry) as a function of rf power, and [F] can be determined. These measurements of [F] complement previous quantitative measurements of CF and radicals [Booth et al., J. Appl. Phys. 85, 3097 (1999); and Cunge and Booth, J. Appl. Phys. 85, 3952 (1999)] made in the same reactor for the same plasma conditions.
Two-dimensional modeling of a microcell plasma in a mixture of Ne/Xe driven by a capacitively coupled high-frequency source89(2001); http://dx.doi.org/10.1063/1.1370360View Description Hide Description
The basic characteristics of a micro-cell plasma in a gas mixture sustained by a high-frequency voltage source with a ring-shaped electrode are described in this article. The key to maintaining a microcell plasma is to reduce wall loss and increase plasma production. The advantage of a gas mixture of Ne/Xe is the increase of the plasma production rate in a low electric field compared to that in pure gas. As a result, a microcell plasma can be sustained by a lower applied voltage by using a gas mixture of Ne/Xe under the same power condition as compared with that in pure Xe.
89(2001); http://dx.doi.org/10.1063/1.1371276View Description Hide Description
Burning voltages of vacuum arcs were measured for 54 cathodematerials and compared with literature data. As anticipated, a correlation between the arc burning voltage and the plasma temperature was found. However, more importantly, a correlation between the cohesive energy of the cathodematerial and the arc burning voltage could be demonstrated. This link between a cathodematerial property, the cohesive energy, and a discharge property, the arc burning voltage, is essential for the operation of the vacuum arc discharge because is determines the plasma temperature.Energy balance considerations show that this “cohesive energy rule” is responsible for several other secondary relationships, such as the correlation between the mean ion charge state and the boiling temperature of the cathode.