A joint experimental and theoretical approach has been developed to study oxygen atom recombination on a beta-quartz surface. The experimental MESOX setup has been applied for the direct measurement of the atomic oxygen recombination coefficient gamma at T(S) = 1000 K. The time evolution of the relative atomic oxygen concentration in the cell is described by the diffusion equation because the mean free path of the atoms is less than the characteristic dimension of the reactor. The recombination coefficient gamma is then calculated from the concentration profile obtained by visible spectroscopy. We get an experimental value of gamma = 0.008, which is a factor of about 3 less than the gamma value reported for O recombination over beta-cristobalite. The experimental results are discussed and compared with the semiclassical collision dynamics calculations performed on the same catalytic system aimed at determining the basic features of the surface catalytic activity. Agreement, both qualitative and quantitative, between the experimental and the theoretical recombination coefficients has been found that supports the Eley-Rideal recombination mechanism and gives more evidence of the impact that surface crystallographic variation has on catalytic activity. Also, several interesting aspects concerning the energetics and the mechanism of the surface processes involving the oxygen atoms are pointed out and discussed.

Carrying out molecular Dynamics simulations is a relevant way for understanding growth phenomena at the atomic scale. Initial conditions are defined for reproducing deposition conditions of plasma sputtering experiments. Two case studies are developed for highlighting the implementation of molecular dynamics simulations in the context of plasma sputtering deposition: Zr x Cu 1-x metallic glass and AlCoCrCuFeNi high entropy alloy thin films deposited onto silicon. Effects of depositing atom kinetic energies and atomic composition are studied in order to predict evolution of morphologies and atomic structure of MD grown thin films. Experimental and simulated X-ray diffraction patterns are compared.

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Energy exchanges due to chemical reactions between a silicon surface and a SF 6 plasma were directly measured using a heat flux microsensor. The energy flux evolution was compared with those obtained when only few reactions occur at the surface to show the part of chemical reactions. At 800 W, the measured energy flux due to chemical reactions is estimated at about 7 W.cm -2 against 0.4 W.cm -2 for ion bombardment and other contributions. Time evolution of the HFM signal is also studied. The molar enthalpy of the reaction giving SiF 4 molecules was evaluated and is consistent with values given in literature.a)

In this work, we employed classical molecular dynamics simulations model to study Zr x Cu 100-x (3 ≤ x ≤ 95) metallic glass films deposited on a silicon (100) substrate. Input data were chosen to fit with the experimental operating conditions of a magnetron sputtering deposition system. The growth evolution is monitored with variable compositions of the incoming atom vapor. The Zr-Zr, Cu-Cu and Zr-Cu interactions are modeled with the Embedded Atom Method (EAM), the Si-Si interaction with Tersoff potential, the Zr-Si and Cu-Si interactions with Lennard-Jones (12-6) potential. Different film morphology and structure were detected and analyzed when the Zr to Cu ratio is varied. The results are compared with X-ray diffraction and Scanning Electron Microscopy analyses of experimentally deposited thin films by magnetron sputter deposition process. Both simulation and experiment results show that the structure of the Zr x Cu 100-x film varies from crystalline to amorphous depending on the elemental composition.

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To cite this version:L Bedra, a L Thomann, N Semmar, R Dussart, J Mathias. Highly sensitive measurements of the energy transferred during plasma sputter deposition of metals. AbstractThis work reports results obtained from heat flux measurements performed during the deposition of metallic thin films by low-pressure plasma sputtering. It introduces a sensitive diagnostic, which allows to perform such measurements directly during the process and to follow in real-time mechanisms involved in plasma/surface interaction. Although quantitative results are provided and discussed, the main scope of this article is a qualitative study of the sputter-deposition process via the energy flux transfers. The diagnostic developed for energy flux measurements is presented and the versatility of the experimental apparatus is described.Results on the study of the deposition of Pt (and Fe) thin films demonstrate a good reproducibility of the measurements and the ability to separate the energetic contributions of the main plasma (∼ 300 mW/cm 2 ) from the deposition process ones (2 to 23 mW/cm 2 ). The influence of gas pressure, plasma power and target bias voltage, on the energy transferred to the silicon substrate is also studied.

To develop heat shields for space vehicles, materials must be characterized in simulation conditions close to those in space environments. The most important conditions for simulating the Earth re-entry phase of space vehicles are achieved through the MESOX set-up associating a 6 kW solar radiation concentrator and a 2450 MHz microwave plasma generator. This paper presents some experimental results for the recombination coefficient γ and the chemical energy accommodation coefficient β in the surface-catalyzed oxygen atom recombination based on experiments performed on the MESOX set-up. This set-up allows both the experimental measurements of the recombination coefficient γ using Optical Emission Spectroscopy and the chemical energy accommodation coefficient β using calorimetry according to a defined protocol. Experimental results are presented for three types of alumina in the temperature range 900-2400 K, for 200 Pa total air pressure. These three alumina differ essentially from their content of sintering additives. This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP: 130.237.165.40 On: Tue, 25 Aug 2015 16:34:18 CP762, Rarefied Gas Dynamics: 24 th International Symposium, edited by M. Capitelli