On the Interaction of a Microwave Excited Oxygen Plasma with a Jet of Precursor Material for Deposition Applications (original) (raw)

Characterization of the Chemical Kinetics in an O2/HMDSO RF Plasma for Material Processing

Advances in Physical Chemistry, 2012

Experimental study of the plasma gas phase in low-pressure radiofrequency discharges of oxygen and hexamethyldisiloxane is presented. The plasma phase has been studied by means of optical emission spectroscopy. Mass spectroscopy of the neutral and of the charged species has been performed too, directly sampling the plasma gas phase, by a dedicated spectrometer. We also measured the ion energy distribution. We have studied the influence of the operating conditions on the plasma gas-phase composition which plays a primary role in the formation process of SiO 2 films, which are known for their important applicative uses.

Controlling the oxygen species density distributions in the flowing afterglow of O2/Ar–O2surface-wave microwave discharges

Journal of Physics D: Applied Physics, 2014

The evolution of species densities along a reactor radially positioned on an O 2 surface-wave microwave discharge is investigated by means of modelling with the aim to define the density tuning possibilities. The validity of the models is shown by the comparison of the calculated and measured axial distribution of O-atoms. The calculations revealed that due to the perpendicular injection of the plasma into the reactor, the gas temperature is close to the room temperature in most of it, except for a 5 cm region around the inlet. It is shown that the pressure drop along the discharge tube, which results in the change of pressure in the discharge region with the gas flow rate, induces the variation of the relative density of active species entering the reactor, where the pressure is kept constant. The surface recombination probability of atoms varies along the afterglow tube due to the surface temperature gradient, as well as due to the conditioning of the surface resulting from the continuous operation of the system. The system is shown to be very practical in applications where surfaces/porous materials are to be treated homogeneously by pumping active species through them, since by tuning the gas flow rate equidensity surfaces can be obtained in the case of the two most abundant species, the O-atoms and O 2 (a) molecules. In the case of O-atoms the densities obtained at the two pressures investigated, i.e. 100 and 50 Pa, are very similar, as well as their evolution along the reactor, while the density of O 2 (a) molecules decreases considerably with pressure.

Effects of Plume Hydrodynamics and Oxidation on the Composition of a Condensing Laser-Induced Plasma

The journal of physical chemistry. A, 2018

High-temperature chemistry in laser ablation plumes leads to vapor-phase speciation, which can induce chemical fractionation during condensation. Using emission spectroscopy acquired after ablation of a SrZrO target, we have experimentally observed the formation of multiple molecular species (ZrO and SrO) as a function of time as the laser ablation plume evolves. Although the stable oxides SrO and ZrO are both refractory, we observed emission from the ZrO intermediate at earlier times than SrO. We deduced the time-scale of oxygen entrainment into the laser ablation plume using an O environment by observing the in-growth of ZrO in the emission spectra relative to ZrO, which was formed by reaction of Zr with O from the target itself. Using temporally resolved plume-imaging, we determined that ZrO formed more readily at early times, volumetrically in the plume, while SrO formed later in time, around the periphery. Using a simple temperature-dependent reaction model, we have illustrated...

Development and Characterisation of a Microwave-heated Atmospheric Plasma Torch

Plasma Processes and Polymers, 2009

Among other applications, microwave plasma sources at atmospheric pressure are used for the decomposition of halogenated volatile organic compounds (VOC). The presented microwave plasma torch is based on an axially symmetric resonator. Simulations of the electric field distribution, Eigen frequency analyses and measurements of the resonant frequency resulted in an improved design. Microwaves of 2.45 GHz are fed into this cavity resulting in a sufficiently high electric field for ignition and maintaining stable plasma. The characterisation of the plasma is made with optical emission spectroscopy. The decomposition of VOC was analysed with FTIR-spectroscopy, a mass spectrometer and an FID.

Effects of O2 Addition on the Discharge Parameters and Production of Reactive Species of a Transferred Atmospheric Pressure Plasma Jet

Applied Sciences

The therapeutic effects of atmospheric pressure plasma jets (APPJs) have been associated with the presence of reactive species, mainly the reactive oxygen and nitrogen ones, generated in this kind of plasmas. Due to that, many studies attempting to enhance the production of reactive species in APPJs have been performed. The employment of gas admixtures, usually mixing a noble gas with oxygen (O2) or water vapor, is one of the most common methods to achieve such goal. This work presents a study of how the addition of small amounts of O2 affects the electrical parameters and the production of reactive species in a transferred APPJ produced at the tip of a long and flexible plastic tube. The study was carried out employing helium (He) as the working gas and applying a high voltage (HV) in the form of amplitude-modulated sine waveform (burst mode). With this configuration it was possible to verify that the O2 addition reduces the discharge power and effective current, as a result of lat...

Role of reactive species in processing materials at laboratory temperature by spray plasma devices

Chemical Papers Slovak Academy of Sciences, 2012

Processing the aerosol of metal salts in non-equilibrium plasma represents a promising technique that combines the advantages of spray pyrolysis with the high reactivity of plasmas at nearlaboratory temperature in order to produce mixed-oxides and perovskite materials. The aim of this paper is to describe the principles of this new technique and to present the various applications and latest developments. This technique's capacity to deposit various mixed metal oxides with precise stoichiometry is demonstrated. It is shown that oxidant plasma species play a key role in the chemical transformation of starting materials into oxides at laboratory temperature, while the configuration of the reactor determines the morphology and texture of the deposited layers. Two different reactor configurations are presented. The porous layers of LaxSr1−xMnO3 as the cathode for fuel cells were synthesised in a wave shock reactor configuration, while nanostructured ZnO-Al layers to form a transparent conductive cathode for photovoltaic cells were deposited in the spray plasma reactor of the latest generation for this technique. The experimental results emphasise the role of plasma species in the rate of chemical reactions and in the chemical composition of the deposited layers.

Investigation of the aluminium oxidation in an oxygen plasma excited by microwaves

Thin Solid Films, 2000

Al-coatings of approximately 50 nm thickness were deposited by thermal evaporation on Si 100 -wafers. The changes of the Al-films during oxygen plasma treatment in a 2.45-GHz microwave discharge at a pressure of 0.1 Pa were investigated. To study Ž . the oxidation kinetics the formed aluminium oxide was investigated using grazing incidence X-ray reflectometry GIXR , XPS Ž . and IR and the residual Al layers were studied using grazing incidence X-ray diffractometry GIXRD . It was observed that Ž . oxygen plasma treatment lead to reactions at low temperatures -300ЊC where thermal treatment show no noticeable effect.

Kinetic aspects of the formation of aluminium oxide by use of a microwave-induced plasma

Analytical and Bioanalytical Chemistry, 2002

The oxidation of thin aluminium layers in a microwave plasma has been investigated to determine the kinetics of oxide growth. Thin Al-coatings were oxidized by means of a variety of gas mixtures, characterized by different partial pressures of oxygen, in microwave-induced plasmas of different power. To study the whole kinetic process the Al-metal and the oxide formed were investigated by means of a combination of grazing incidence X-ray reflectometry (GIXR) and grazing incidence X-ray diffractometry (GIXRD). XPS and FTIR spectroscopy confirmed the formation of stoichiometric Al2O3 . The alumina formed is X-ray amorphous. Quantitative description of oxide formation was achieved indirectly by determination of the decrease in the integrated intensity of the Al(111)-peak and the total thickness of the whole coating. These values enabled calculation of kinetic data. It was found that oxide growth was a combination of two simultaneous processes – diffusion and sputter processes. The diffusion coefficient D (cm2 s–1) and the sputter rate S (nm s–1) were determined. The effect of the composition of the gas mixture, microwave power, and concentration of activated oxygen species on the oxidation process will be discussed. For calculation of the activation energy, EA, of this plasma-enhanced diffusion process the temperature-dependence of D was investigated.