Philippe Belenguer

Improvement of the analytical performance in RF-GD-OES for non-conductive materials by means of thin conductive layer deposition and the presence of a magnetic field

Radiofrequency glow discharge coupled to optical emission spectrometry (RF-GD-OES) is a well-known analytical technique for bulk, surface and depth profiling and can be applied in the direct analysis of conductors, semiconductors and non-conductors, however for the latter case limits still exist. The problem is related to the low power deposited in the plasma due to a voltage drop developing inside the material. The voltage transfer coefficient, defined as the ratio between the peak voltage at the front and at the back of the sample. This depends on the sample capacitance, which itself is dependant on the material surface, thickness and permittivity. In order to improve the analysis of such non-conductive materials, thin conductive top layers are deposited on both sides of the sample which increases their voltage transfer coefficient. The aim of this work is to study the influence of these thin layers on the optical and electrical signals measured for the samples with varying thickness and diameter. Additionally, the influence of applying a magnetic field during the GD analysis has been evaluated as an attractive option in order to obtain higher sputtering rates, together with better ionisation and excitation efficiencies and as a consequence give improved emission intensities.

Improve the luminous efficacy of dielectric barrier discharge xenon lamp

Xenon excimer dielectric barrier discharge is a good candidate for free mercury lightning. The studied device1 is consisting of two glass plates separated by a constant gas gap. The glass thickness is 4 mm and the gap 2 mm. A transparent conducting material (electrode) has been deposited on both external sides (plane to plane electrodes) and white phosphors2 on both internal sides of the dielectric. The lamp is filled with Neon-xenon gas mixture and operates in a pressure range of 100-400 torr. In a previous work1, for sinusoidal and pulsed excitations, we have shown the influence of the applied voltage (amplitude and frequency) on the consuming power, the light emission and mostly on the homogeneity of the discharge (modeling and experimental works).

Spatial emission behaviour of dielectric barrier discharge lamp driven by sinusoidal or pulsed voltage excitation

Xenon excimer dielectric barrier discharge is a good candidate for free mercury lamp. The studied device is consisting of two glass plates separated by a constant gas gap. The glass thickness is 4 mm and the gap 2 mm. A transparent conducting material (electrode) has been deposited on both external sides and phosphors (white emitting powders) on both internal sides of the dielectric. The lamp is filled with rare gas mixture and operates in a pressure range of 100-400 torr. A sinusoidal or a pulsed excitation voltage can be used up to 3000 V in a frequency range of 10-50 kHz. In a previous work for sinusoidal excitation, we shown the influence of the applied voltage (amplitude and frequency) on the consuming power, the light emission and mostly on the non-homogeneity of the discharge. Using a 2 dimensional model developed in our laboratory, the effects of the applied voltage (amplitude and frequency) and the pressure will be studied. Particularly on the distance between the streamers when the discharge is not homogeneous. In this work, for pulsed excitation, we will present some results concerning a Ne-Xe 50% mixture for three different pressures and we will discuss the influence of the applied voltage (waveforms, amplitude and frequency) on the consuming power, the light emission (ICCD and luminance) and mostly on the spatial emission of the discharge. We will also compare experimental results between sinusoidal and pulsed excitations.

Experimental and numerical characterization of an argon RF inductively coupled plasma for surface treatment

Summary form only given. Plasma-surface interactions depend highly on plasma parameters offering an appreciable versatility on the use of plasma discharges for surface treatment applications including surface cleaning, surface etching, wettability and adhesion increase, friction reduction, cell attachment improvement and surface-protein interactions alteration. This work is supported by the French public funding agency OSEO and aims to provide surface treatment solutions with an Inductively Coupled Plasma (ICP) source. Prior to any treatment attempt, experimental and numerical diagnostics have been conducted on an ICP discharge in argon in order to obtain a better understanding of the plasma behavior and properties. In our experimental setup, the discharge is generated with a 13.56 MHz radiofrequency ICP source within a cylindrical quartz tube. The tube is connected to a separate process chamber where samples to be treated may be inserted. The gas parameters are the argon flow rate (<; 500 sccm) and the pressure (<; 1 mbar). Optical emission spectroscopy diagnostics are conducted with an Automated Imaging Spectrometer (iHR320 Horiba Jobin Yvon) and a Princeton Instruments PI-MAX intensified CCD camera. Moreover, Langmuir Double Probe diagnostics are done with an Impedans ALP Sytem (Impedans Ltd). Simultaneous measurements are performed through different reactor openings for spatio-temporal characterization. In parallel, a time dependent 2 dimensional fluid model is developed for comparison purpose1. The numerical model is applied to a simplified 2D geometry corresponding to the experimental chamber with pure Ar gas. In both numerical and experimental domain, the influence of various parameters, particularly gas pressure and injected power, are studied. In this work, basic plasma characteristics such as optical emission and electron temperature in the chamber will be provided. In addition, comparison between the experimental and simulation results will be presented.