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In this paper the evolution of species densities up to the saturation limit in pulsed dielectric barrier discharges in atmospheric air plasma is predicted. The saturation limit itself is presented in the form of an exponential equation and is validated by computer modeling of continuity equations and atmospheric reactions coupled with appropriate dielectric dependent boundary conditions. Microdischarge streamer times are treated independently and a profile of the species generation due to all microdischarges within the plasma is presented. Quasi-neutrality is assumed for calculations and a theoretical maximum value for species densities in such a plasma is additionally outlined. Results show a good agreement between simulated and calculated values and serve to illustrate the onset of saturation in atmospheric pressure plasmas in general. Practical conditions of voltage, gap distance and frequency are incorporated so as to make the model as realistic as possible.

A novel multielectrode dielectric-barrier discharge plasma system operating at atmospheric pressure in air, which has improved microbial inactivation properties is described. The interaction of high-voltage components necessary to create the discharge is outlined, and the unique configuration of electrodes driven by power insulated gate bipolar transistors is put forward. Active species gain is in evidence in this system due to the effective feedforward mechanism employed and are validated by carrying out microbial inactivation studies on E. coli. Both active species gain and microbial inactivation hypotheses are verified by numerical modeling.

Dielectric breakdown in ceramics and composites has previously been determined by the dielectric breakdown model, dependent only on the electric field strength at a certain point and intermolecular distance in a lattice. This does not take into account quantum aspects of the lattice structure into account. The present model takes into account quantum variations of particles in conjunction with different particle characteristics. Dielectric breakdown patterns are characterised by their quantum breakdown probabilities and studies are carried out as a function of the applied electric field, temperature and specific material constants responsible for breakdown, such as the mean free path and the potential barrier present.

Summary form only given. A novel multi-electrode dielectric barrier discharge (DBD) plasma system exhibiting active species gain is examined for the production of ozone gas and hence microelectronic substrate treatment. This species gain is achieved by having four electrode pairs in a vertical arrangement and supplying compressed air to traverse throughout the system. This forces the filamentary striations together through lateral pressure, thus aiding in the formation of an extremely dense plasma. The multi-electrode system operates in an effective feed-forward mechanism to create a denser plasma than reported previously. By increasing the initial conditions for oxygen metastables and radicals, singlet oxygen atoms and other reactive species, the overall density is also increased for successive electrode pairs. Additionally, existing plasma technologies for ozone production require the sample to be treated within the plasma volume. Due to the forced nature of the plasma flow, indirect treatment is possible and all results reported here are based on this. Tests on mica and silicon for the semiconductor industries were performed and compared with existing ozone treatment technologies. Results indicate that sufficient surface chemical changes were in evidence with only 30 seconds of plasma treatment. These were obtained by microscopic analysis using scanning electron microscopy (SEM) and Raman spectroscopy in addition to contact angle/wickability tests. These results compare excellently with standard 45-minute treatments of existing technology indicating that this novel plasma system could be used to produce similar quantities of ozone in roughly 1.1% of the time to standard ozone treatment apparatus. In particular this research has enormous potential in industry due to the high concentration of ozone produced coupled with the prospective in-line set-up of the system. Microelectronic sensors were fabricated from these substrates and functioned in a similar manner to existing sensors, i.e. with almost 45 minutes cut from the manufacture time.

Summary form only given. In this paper, optical and electrical measurements of a novel multi-electrode dielectric barrier discharge (DBD) plasma system exhibiting active species gain are performed. This gain in species density is accomplished by arranging four electrode pairs vertically and forcing compressed air through their volumes. This forces the filamentary striations together through lateral pressure, thus aiding in the formation of an extremely dense plasma. The multi-electrode system operates in an effective feed-forward mechanism to create a denser plasma than reported previously. By increasing the initial conditions for oxygen metastables and radicals and other reactive species at each electrode pair, the overall density is increased also for successive electrode pairs. Optical measurements are performed by means of a photomultiplier tube with a quartz window (electron tubes module P30232-07) in order to analyse the deep UV region of the spectrum accurately. These are taken at each of the four electrode stages and at the output of the system. The copious quantities of ozone produced in this DBD plasma are evident from focusing in on the 250-260 nm regime and analysing the associated optical emissions. In addition, the electrical measurements from the quad IGBTs acting as the drive circuitry are analysed and drive circuitry is outlined to create as noiseless an environment as possible. Results indicate that the optical emission around the 250 nm mark throughout the system increases thus showing the increase in the concentration of species with this characteristic wavelength from one plasma volume to the next. The output of the system shows a high density of these species, gradually diminishing as diffusion takes over. The need for compressed air is additionally highlighted by the individual DBD striations being clearly visible when it is not applied. This results in little or no species gain as no accelerant exists in the system. This research has enormous potential in industrial applications due to the high concentration of ozone produced coupled with the prospective in-line set-up of the system.

Summary form only given. This paper outlines specific variations in recombination coefficients for charged particles (electrons and ions) and how these variations affect the onset of saturation of atmospheric pressure dielectric barrier discharges (DBDs). By solving continuity equations for electrons and ions, with the application of dielectric dependent boundary conditions, in conjunction with the Boltzmann equation, the effect of different recombination processes was modeled numerically. Incorporation of previously unconsidered atmospheric reactions into the continuity equations make this model unique for atmospheric air DBDs. The dependence of the recombination processes on kinetic temperature, field drift and autoionization were investigated and each pulse of the applied AC electric field was considered up to a saturation threshold. Results show a strong dependence of the kinetic temperature of electrons on the recombination coefficient and it was additionally found that the plasma approached saturation more quickly when autoionization was considered.

peer-reviewed Ozone (03) is potentially hazardous to human health and accurate prediction and measurement of this gas is essential in addressing its associated health risks. This paper presents theory to predict the levels of ozone concentration emittedfrom a dielectric barrier discharge (DBD) plasma for ozone sensing applications. This is done by postulating the kinetic model for ozone generation, with a DBD plasma at atmospheric pressure in air, in the form of a set of rate equations. Rate constants are taken from the literature and previously unconsidered ozone producing hydroxyl reactions are incorporated into the work, yielding more accurate results for the concentration of ozone for sensing applications. An application of this work is that knowing levels of ozone produced within an atmospheric DBD plasma allows for ozone sensors to be more accurately tuned to the particular requirements of the plasma system.

Breakdown in dielectric layers has previously been assumed to be dependent only on the electric field strength at a certain point in the dielectric lattice [1], [2]. This does not take quantum aspects of the lattice structure into account. The present model takes into account quantum variations of particles in conjunction with different particle characteristics. Dielectric breakdown patterns are characterised by their quantum breakdown probabilities and studies are carried out as a function of the applied electric field, temperature and specific material constants responsible for breakdown, such as the mean free path and the potential barrier present. How these quantities affect the breakdown probability of the dielectric layer is examined and this facilitates the prediction of failure in dielectric layers in semiconductor devices.