Volume 91, Issue 1, 01 January 2002
Index of content:
- PLASMAS AND ELECTRICAL DISCHARGES (PACS 51-52)
91(2002); http://dx.doi.org/10.1063/1.1420765View Description Hide Description
Underwater sparks have long been used in many fields, but up until now there are no widely accepted model for them. In this article we present a more practical model for them, taking into account the nature of the plasma of pulsed discharge in water, where the following corrections are included: (1) correction of the ionization potentials; (2) pressure caused by the effect of charge interaction on the bound state electrons; (3) line spectra; and (4) mass flow caused by evaporation, condensation, and bubble wall ablation. Using this model, the time-varying pressure, temperature, and density can be obtained for given circuit parameters. The simulation results are in good agreement with the experimental measurements. We also give a simulation with capacitance of 1.25 nF, initial voltage of circuit inherent inductance of 20 nH, and circuit resistance of 15 mΩ; the maxima of the pressure, temperature, and electron density are about and respectively.
91(2002); http://dx.doi.org/10.1063/1.1421239View Description Hide Description
The ion impact energy and angle distributions at the interior sidewall of a large cylindrical bore in the presence of an auxiliary electrode for plasma sourceion implantation are determined. A collisional model is developed for cylindrical bore geometry by using Monte Carlo techniques. The ion-neutral charge exchange and momentum-transfer cross sections that depend on the ion energy are taken into account precisely. The simulation results for ions implanting into the target for different pressures are given and the relationship between the distributions and the pressure of the neutral gas is investigated.
91(2002); http://dx.doi.org/10.1063/1.1421034View Description Hide Description
A drift tube-double mass spectrometer technique has been used to study the transport of in and of in The reduced mobilities of these two ions were measured over the density-normalized electric field strength between 30 and 750 Td It was found that substantial amounts of were produced thorugh the reaction of with Ar. Thus, the mobility of could be measured over the range from 30 to 260 Td. Further measurements of the abundance of secondary ions formed by the reactions of and with Ar revealed that for and respectively, predominates as a secondary species over and The injection of into was also found to be a very efficient dissociative charge transfer process, leading predominantly to formation, with conversion efficiencies of practically for The above finding is consistent with a previous beam study.
Modeling and analysis of hydrogen–methane plasma in electron cyclotron resonance chemical vapor deposition of diamond-like carbon91(2002); http://dx.doi.org/10.1063/1.1421038View Description Hide Description
Diamond-like carbon films were deposited using the electron cyclotron resonancechemical vapor deposition (ECR-CVD) system. A model for the ECR plasma was formulated using deposition parameters, such as microwave power, pressure, and hydrogen/methane ratio as inputs. Using the model, electron energy, rate constant of electron impact reactions, and density of species in the plasma are calculated. The outputs of the model are analyzed as a function of deposition conditions, such as microwave power, pressure, and hydrogen/methane ratio and compared to experimental data measured using a Langmuir probe. The results show that ion density increases following the increase in microwave power and hydrogen/methane ratio, and decreases following the increase pressure. Results from the model are in agreement with experimental data, and show that the main neutral species are H, CH, and The main ionic species are and
91(2002); http://dx.doi.org/10.1063/1.1419208View Description Hide Description
Low-temperature nitridation of 3 nm films using and remote radio frequency (rf)plasmas was investigated. On-line Auger electron spectroscopy and angle-resolved x-ray photoelectron spectroscopy (ARXPS) were employed to determine the concentration, spatial distribution, and local chemical bonding of nitrogen in the resultant films. Experiments were performed using a substrate temperature of 300 °C and 30 W rf power. Nitridation using an upstream remote plasma at 0.1 Torr incorporates nitrogen at the top surface of the film. In contrast, a lower concentration of nitrogen distributed throughout the film is obtained when the process pressure is increased to 0.3 Torr. ARXPS indicates a local bonding configuration, irrespective of the spatial distribution of N atoms. Slightly more nitrogen is incorporated using a downstream plasma at each process pressure. By comparison, nitridation of films using a remote plasma at 0.1 Torr is very slow. Optical emission spectroscopy indicates that He dilution enhances the generation of species by altering the plasma electron energy distribution and by providing an additional kinetic pathway (Penning ionization). Changing the remote plasma configuration from upstream to downstream (at 0.1 and 0.3 Torr) also enhances generation. For upstream remote plasmas, the intensity of first positive emission from states increases with pressure, whereas the first negative emission from states decreases. We infer from these observations that species are primarily responsible for top surface nitridation at 0.1 Torr, and that neutral species metastables and N atoms] are associated with sub-surface nitrogen incorporation.