O. Leroy

Generation and confinement of microwave gas-plasma in photonic dielectric microstructure.

We report on a self-guided microwave surface-wave induced generation of ~60 μm diameter and 6 cm-long column of argon-plasma confined in the core of a hollow-core photonic crystal fiber. At gas pressure of 1 mbar, the micro-confined plasma exhibits a stable transverse profile with a maximum gas-temperature as high as 1300 ± 200 K, and a wall-temperature as low as 500 K, and an electron density level of 10¹⁴ cm⁻³. The fiber guided fluorescence emission presents strong Ar⁺ spectral lines in the visible and near UV. Theory shows that the observed combination of relatively low wall-temperature and high ionisation rate in this strongly confined configuration is due to an unprecedentedly wide electrostatic space-charge field and the subsequent ion acceleration dominance in the plasma-to-gas power transfer.

Determination of titanium temperature and density in a magnetron vapor sputtering device assisted by two microwave coaxial excitation systems

We present an optical absorption diagnostic technique devoted to the simultaneous determination of titanium density and temperature during sputtering of Ti. These measurements were performed in a type of ionized physical vapor deposition reactor, consisting of a magnetron sputtering device assisted by two microwave systems for the ionization of the sputtered vapor of the magnetron. Our goal is to optimize the ionization in this reactor in order to improve the deposition process (film quality, recovery of the layers, etc.) compared to standard magnetron sputtering systems. In order to determine both titanium neutral and ion densities, we have used a titanium hollow cathode vapor lamp powered with pulsed power supply. Measurements were carried out at different positions in the reactor at different pressures (1–15 Pa). We have studied the effect of magnetron current from 100 mA to 2 A and of microwave power from 100 W to 1 kW. At lower pressures, we have shown that the titanium is not thermalized close to th...

New type of plasma reactor for thin film deposition: magnetron plasma process assisted by microwaves to ionise sputtered vapour

Abstract A new type of plasma reactor for thin film deposition has been designed: a magnetron-sputtering device assisted by microwave applicators to ionise the sputtered vapour of the magnetron. Ionizing the vapour has several advantages: improvement of the film quality, deposition on substrates with complex shapes, enhancement and control of the reactivity. The reactor consists of a planar rectangular magnetron cathode (22 cm×9 cm) and of two coaxial-type microwave applicators located perpendicularly to the substrate–magnetron axis, on both sides of the sputtered vapour flow. This reactor can operate on a wide pressure range: from 0.2 to 60 Pa. Several in-situ diagnostics have been performed to characterise the process in argon gas with chromium and titanium targets. Electron density of the order of 10 11 –10 12 cm −3 and electron temperature of 1.5–2 eV were measured in the microwave plasma by a cylindrical Langmuir probe; emission of metallic ions (Cr + , Ti + ) was clearly identified when the microwave plasma is turned on; concentration of Cr or Ti atoms was measured by absorption spectroscopy, a decrease of this concentration is observed when the microwave power is increased. Characterisation of thin titanium films was performed ex-situ by Rutherford backscattering spectroscopy (RBS) for Ti content and nuclear reaction analysis (NRA) for oxygen contamination. Film density was deduced from RBS and NRA measurements and X-ray reflectometry. Oxygen contamination in the film is clearly decreased when microwave plasma is turned on and with a bias applied to the substrate.

Fundamental aspects in non-reactive and reactive magnetron discharges

In this paper, which deals with physical processes and problems that are involved in magnetron discharges used for the deposition of thin films and material coatings, we emphasize the aspects connected to discharge physics: energy deposition, behaviour of the discharge in reactive gases in connection with plasma–surface interactions. We also present recent works on ionized physical vapour deposition (IPVD) in which the usual PVD magnetron sputtering is assisted by an additional discharge in order to ionize the sputtered neutral vapour and to achieve a better control and quality of the deposited material in industrial applications. We restrict ourselves to planar magnetrons.

Hydrodynamic and thermal effects of continuous microwave-sustained plasma in capillary tubes

Argon micro-plasmas can be generated at low power (10–100 W) in hollow-core capillaries 100–700 μm in diameter and over a few cm in length using continuous wave (CW) microwave surfatron excitation at 2.45 GHz. Electromagnetic simulations have been performed in order to design the surfatron cavity for optimal discharge ignition and stable plasma CW operation. The plasma characterization was carried out by optical emission spectroscopy on excited species present as impurities in argon. The rotational spectra of OH molecules were used to determine the gas temperature, and Stark broadening of the H β line was used to obtain the electron density. The gas temperature turns out to be in the 500–1200 K range along the plasma column, and the maximum electron density (at the surfatron gap) in the 8  ×  1014–5  ×  1015 cm−3 range. The electron density was also obtained by a semi-empirical analysis of the power coupled to the plasma along the axial direction and was found to be in good agreement with the Stark measurements. The hydrodynamic and thermal effects of plasma were investigated by the modelling of neutral gas flow and heat transfer which is of interest for the remote control of gas flow properties along the capillary.

Microwave resonator for generation of microplasmas in hollow-core photonic crystal fibers

We report on new class of microwave resonator enabling generation of a stable microplasma in 100 μm core-diameter kagome-latticed HCPCF without any structural damage. Blue Ar+ lines are successfully generated with low microwave power.

Generation of surface-wave microwave microplasmas in hollow-core photonic crystal fiber based on a split-ring resonator.

We report on a new and highly compact scheme for the generation and sustainment of microwave-driven plasmas inside the core of an inhibited coupling Kagome hollow-core photonic crystal fiber. The microwave plasma generator consists of a split-ring resonator that efficiently couples the microwave field into the gas-filled fiber. This coupling induces the concomitant generation of a microwave surface wave at the fiber core surround and a stable plasma column confined in the fiber core. The scheme allowed the generation of several centimeters long argon microplasma columns with a very low excitation power threshold. This result represents an important step toward highly compact plasma lasers or plasma-based photonic components.

Recent Developments on Ionized Physical Vapour Deposition: Concepts, Determination of the Ionisation Efficiency and Improvement of Deposited Films

While most of the IPVD reactors use radio-frequency (RF) coils to create additional ionization, we developed an alternative technique consisting of a home made magnetron sputtering device in which the ionization of the emitted sputtered vapor is achieved by two microwave antennas. Langmuir probe measurements were used to determine electronic density and temperature. Emission optical spectroscopy has been performed and argon and titanium line intensities have been measured, showing an increase of Ti+* to Ti* line intensity ratio. Optical absorption spectroscopy using a titanium hollow cathode lamp powered with a pulsed power supply has also been performed to determine the ionized fraction of the sputtered vapor. Preliminary results are also given for a conventional IPVD system (with RF loops) used for the deposition of Ti-based biomaterials.