Larbi Bedra

Direct measurements of the energy flux due to chemical reactions at the surface of a silicon sample interacting with a SF6 plasma

Energy exchanges due to chemical reactions between a silicon surface and a SF6 plasma were directly measured using a heat flux microsensor (HFM). 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 SiF4 molecules was evaluated and is consistent with values given in literature.

Molecular Dynamics simulations of clusters and thin film growth in the context of plasma sputtering deposition

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: ZrxCu1-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.

Highly sensitive measurements of the energy transferred during plasma sputter deposition of metals

This 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 us to perform such measurements directly during the process and to follow in real-time mechanisms involved in the plasma/surface interaction. Although quantitative results are provided and discussed, the main scope of this paper 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 contribution of the main plasma (~300?mW?cm?2) from the deposition process contribution (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.

Atomic Oxygen Recombination and Chemical Energy Accommodation on Alumina at High Temperature

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 sinterin...