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Neutral gas temperature (Tg) is measured in an industrial high-density inductively coupled etch reactor operating in CF4, SF6, O2, Cl2, or HBr plasmas. Two laser diodes are used to deduce Tg from the Doppler widths of 772.38 and 811.5nm lines absorbed by Ar*(P23) metastable atoms, when a small amount of argon (5%) is added to the gas flow. With the 811.5nm beam passing parallel to the wafer, Tg near the wafer surface is obtained by laser absorption technique. With the 772.38nm beam entering the top of the reactor perpendicular to the wafer surface, the volume averaged temperature is deduced by laser induced fluorescence technique. The volume averaged Tg increases with radio frequency power and with pressure, although the temperature near the walls is only weakly dependent on gas pressure. The main effect of increasing the pressure is an enhancement of the temperature gradient between the discharge center and the wall boundary. Due to the thermal accommodation, the authors always observe a significant temp...

The reactions of Ar(4s 3 P 2 ) and Ar(4s' 3 P 0 ) metastable atoms with H 2 and D 2 have been studied at 300 and 80 K by the stationary and flowing-afterglow techniques. Total quenching constants were measured for both metastable atoms for H 2 and D 2 at 300 K and for H 2 at 80 K. Optical pumping in the stationary-afterglow experiment was used to select one or the other metastable atoms, and chemiluminescence spectra were obtained for state-selected metastable atoms reacting with H 2 and D 2 . The branching fractions for chemiluminescence, which range from 0.07 to 0.30, are higher for D 2 than H 2 and higher for Ar(4s' 3 P 0 ) atoms than for Ar(4s 3 P 2 ) atoms. The chemiluminescence is assigned to the ArH(B 2 Π-X 2 Σ + ) and ArD(B 2 Π-X 2 Σ + ) transitions. The total quenching rate constants for H 2 decline by factors of 80 and 30 at 80 K. relative to the room-temperature values, for the reactions of Ar(4s 3 P 2 ) and Ar(4s' 3 P 0 ) atoms, respectively. Both the chemiluminescence and dark product channels of these reactions probably proceed by chemical reaction rather than by electronic energy transfer.

We have developed both Atomic Layer Epitaxy (ALE) and atomic absorption (AA) techniques in a Molecular Beam Epitaxy (MBE) machine in order to grow atomically flat superconducting thin films of DyBaCuO. We describe the main characteristics of these techniques and their effects on the properties of the films.

This paper discusses the possibility of producing high concentrations of O 2 (a 1 Δ g ) states at pressures up to atmospheric in rare-gas/oxygen/NO mixtures by using micro-plasmas. Micro-plasmas refer to electric discharges created in very small geometries which have been proven able to operate in DC mode at high pressure and high power loading without undergoing any glow to arc transition. The so-called Micro Cathode Sustained Discharge (MCSD), which is a three-electrode configuration using a Micro Hollow Cathode Discharge (MHCD) as a plasma cathode, can be operated as a non-self-sustained discharge with low values of the reduced electric field and of the gas temperature. As a result, these MCSDs can efficiently generate large amounts of singlet delta oxygen. In Ar/O 2 /NO mixtures, at an oxygen partial pressure of 10 mbar, high values of O 2 (a 1 Δ g ) number density (1.5 10 16 cm -3 ) and of the production yield (6.7 %) can be simultaneously obtained. For lower O 2 partial pressure, yields higher than 10 % have been measured. In He/O 2 /NO mixtures, O 2 (a 1 Δ g ) number densities around 10 16 cm -3 were achieved at atmospheric pressure for flow rates in the range 5-30 ln/mn, which could give rise to new applications.

International audience; Broad band absorption spectroscopy is widely used to measure the concentration of radicals, which is important to understand the physical chemistry of many plasmas. It is possible to increase the sensitivity of this technique and to perform time-resolved measurement by using light emitting diodes (LEDs) as a light source. The method is applied to detect CF2 radicals and Cl2 molecules in high density plasmas. The detection limit over 10ms integration time is as low as 3mTorr of Cl2. We conclude that the absorption spectroscopy with LEDs opens possibilities for precise process control and fundamental analysis of reactive media.

In rare gas/oxygen mixtures, the generation of O2(a∆g) states by microplasmas has been studied experimentally and theoretically. Microplasmas refer to electric discharges created in very small geometries able to operate in DC mode at high pressure without glow to arc transition. A microplasma configuration which has proven to be stable at atmospheric pressure and up to a power density of some 100 kW/cm is the Micro Hollow Cathode Discharge (MHCD) developed by Schoenbach and coworkers. MHCDs are created by applying a voltage between two closely spaced hollow electrodes separated by a dielectric layer. The thickness of the dielectric and the diameter of the hole are both on the order of some 100's microns. These MHCDs can be used as plasma cathodes for generating a diffuse discharge between the MHCD cathode and a third positively-biased electrode placed some distance away. This is the so-called Micro Cathode Sustained Discharge (MCSD) configuration. It is shown in the present paper that these MCSDs can be operated as nonself-sustained discharges with low values of the reduced electric field and of the gas temperature. As a result, these MCSDs can efficiently generate large amounts of singlet delta oxygen. In argon-oxygen mixtures, O2(a∆g) relative yields of 13 % were measured 23 cm downstream in the afterglow of the MCSD discharge, while in helium-oxygen mixtures, O2(a∆g) number densities above 10 cm were achieved at atmospheric pressure for flow rates in the range 5-30 ln/mn. Moreover, it has been demonstrated that MCSDs can be operated in parallel in this non-self-sustained discharge mode. Such arrays of MCSDs offer a new possibility to produce large amounts of O2(a∆g) states, which could give rise to a large spectrum of applications

Arrays of microcathode sustained discharges were developed for the production of singlet delta oxygen (SDO) at atmospheric pressure. SDO densities higher than 3.5×1016 cm−3 have been efficiently produced and transported over distances longer than 50 cm. These arrays appear to be an ideal tool for examining the reactivity of SDO with biological components. Experiments were performed indicating that SDO is able to oxidize 2′-deoxyguanosine, a DNA constituent. It is shown that the 4-OH-8-oxodGuo formation is proportional to the number of SDO molecules while other reactive species could also be involved in the production of the nucleosides dSp and dZ.

We report experimental results showing that singlet oxygen O2(aΔ1g) can be efficiently produced at atmospheric pressure in a three-electrode microcathode sustained discharge (MCSD) configuration. This configuration consists of a microhollow cathode discharge (MHCD) acting as a plasma cathode to sustain a stable glow discharge between the MHCD and a third planar electrode placed at a distance of 8 mm. Experiments were performed in He/O2/NO mixtures. O2(aΔ1g) number densities higher than 1016 cm−3 were measured in the MCSD afterglow at total flow rates up to 30 ln/mn, resulting in O2(aΔ1g) fluxes above 10 millimole per hour (mmol/h).

In this paper, we report the influence of the various stages of the preionized high power pulsed magnetron discharge on the saturated ion substrate holder current. Our system allows superposition of a preionization low current dc discharge with high voltage pulses applied directly on the magnetron cathode. This system is characterized by a very fast and perfectly reproducible discharge current rise. For a 33?mm copper target, Ar pressure of ~1?Pa, voltage applied in a pulse of ~1?kV, the maximum cathode current of ~40?A is reached in 6??s. The dependence of the saturated ion substrate holder current was analyzed for varying time duration of the high power pulse from 2 up to 8??s by 0.5??s steps. It allows the discrimination of the contribution of elemental temporal intervals to the overall saturated ion substrate holder current. This analysis led to the conclusion that the transport of ballistic ions during the current pulse and in the afterglow is independent of time. We concluded that space charge effects are negligible for both discharge and post-discharge conditions and that electrons act as a neutralizing background. Finally, on the basis of a phenomenological kinetic model for the electron transport, physical explanations of these results are proposed which involve the transverse diffusion of low energy electrons out of the magnetized glow region through electron?ion Coulomb collisions.