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.

Ozone sensing properties of mixed oxides of In 2 O 3, ZnO , and SnO 2 in the form of thin films are explored. Exposure to ozone causes defects in the materials, and subsequently causes changes in the materials properties. In this work, a cost-effective, room temperature, real-time ozone monitoring device has been developed. The fabricated sensors are capable of detecting threshold ozone safety levels proposed by the World Health Organization (WHO) while operating at room temperature. Room temperature operation offers many advantages over high temperature operation, such as reduced power consumption, reduced fabrication costs, and ease of implementation into portable devices, such as laptops and mobile phones. The fabrication of these sensors was carried out by means of an Edwards E306A Coating System. Various mixtures of In 2 O 3, ZnO , and snO 2 were deposited in a rectangular pattern on top of copper interdigitated electrodes. X-ray Photo Spectroscopy (XPS) analysis showed that there were levels of impurities in the sensor samples, which were dependant on the fabrication process and parameters. XPS analysis also gave a detailed account of the shifts in binding energies of the thin oxide layers. The results presented show that the highest response to environmentally relevant ozone concentrations is achieved with a very thin sensing layer and a high deposition rate. The performance of the sensors has been investigated and compared.

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.

Both gamma radiation and ozone sensing properties of mixed oxides in the form of thin films are explored. External effects, such as radiation and ozone, cause defects in the materials it interacts with and, consequently, it causes changes in their properties. These changes manifest themselves as the alterations in both the electrical and the optical parameters, which are being measured and employed for dosimetry sensor development. An Edwards E306A thermal coating system was used for In 2 O 3 :ZnO:SnO 2 (90%:5%:5%) films deposition. For the electrical properties measurements, Cu electrodes were manufactured on the glass substrate via thermal evaporation of Cu; then AZ5214 photoresist was spin-coated over it and exposed to ultraviolet (UV) light via the acetate, containing the desired electrodes patterns. After the exposure, the substrate was placed in Electrolube PDN250ML developer solution and then rinsed in water and placed in the etching solution of SEMO 3207 fine etch crystals to reveal the electrode pattern. The optical properties of In 2 O 3 :ZnO:SnO 2 thin films were explored using CARY 1E UV–visible spectrophotometer. The values of the optical band gap E opt are estimated in the view of the Mott and Davis’ theory. Doping of In 2 O 3 with 5% ZnO and 5% SnO 2 dramatically changes the overall structure of the film and thus affects its sensing to gamma radiation and ozone. Mixing metal oxides in certain proportions provides a tool for controlling the sensors response.

Ozone sensing properties of mixed oxides of In2O3, ZnO, and SnO2 in the form of thin films are explored. Exposure to ozone causes defects in the materials, and subsequently causes changes in the materials properties. In this work, a cost-effective, room temperature, real-time ozone monitoring device has been developed. The fabricated sensors are capable of detecting threshold ozone safety levels proposed by the World Health Organization ( WHO) while operating at room temperature. Room temperature operation offers many advantages over high temperature operation, such as reduced power consumption, reduced fabrication costs, and ease of implementation into portable devices, such as laptops and mobile phones. The fabrication of these sensors was carried out by means of an Edwards E306A Coating System. Various mixtures of In2O3, ZnO, and snO(2) were deposited in a rectangular pattern on top of copper interdigitated electrodes. X-ray Photo Spectroscopy (XPS) analysis showed that there were levels of impurities in the sensor samples, which were dependant on the fabrication process and parameters. XPS analysis also gave a detailed account of the shifts in binding energies of the thin oxide layers. The results presented show that the highest response to environmentally relevant ozone concentrations is achieved with a very thin sensing layer and a high deposition rate. The performance of the sensors has been investigated and compared.

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.

Thin films of Indium-zinc-tin oxide have been prepared by Vacuum Thermal Evaporation (VTE). The sensing characteristics of these films to environmentally relevant ozone concentrations were studied at room temperature. The effects of film thickness, deposition rate and annealing were investigated. The resistance of the thin film was found to be inversely proportional to the deposition rate. The highest sensitivity of the ozone sensors was found at a deposition rate of 1.2 nm/s - 1.4 nm/s. In addition the O 3 sensors were found to perform best with a 40 nm thick sensing layer. ln 2 O 3 , ZnO and SnO 2 were deposited on alumina substrates containing interdigitated electrodes by means of VTE. These results have shown that In 2 O 3 :ZnO:SnO 2 thin films prepared by VTE method are promising for room temperature ozone sensing.

A new type of highly sensitive ozone (O3) metal oxide gas sensor has been developed. Various mixtures of ln2O3, ZnO and SnO2 were deposited on alumina substrates containing indigitated electrodes by means of vacuum thermal evaporation (VTE). Deposition rate of the sensing layer was varied from 0.3 nm/s-1.4 nm/s. The highest sensitivity of the sensors was found at a deposition rate of 1.2 nm/s-1.4 nm/s. In addition the O3 sensors were found to perform best with a 40 nm thick sensing layer. With such sensors, environmentally relevant ozone concentrations can be measured (0-500 ppb (parts per billion)). Different combinations of this material were investigated and compared focusing on the sensitivity and performance when exposed to ozone. Most of the current metal oxide ozone sensors on the market have the disadvantage of requiring operation at elevated temperatures (200degC-600degC). Room temperature operation has some major advantages over elevated temperature operation such as, reduced fabrication costs, reduced operating costs, as well as ease of implementation into portable/handheld devices.