Electron Cyclotron Resonance Discharge Research Articles

Plasma-assisted growth of bilayer silicon-containing coatings for hardness and corrosion resistance

Hard corrosion-resistant bilayer coatings were grown in a high-density microwave electron cyclotron resonance discharge. The bilayer coatings consist of a relatively soft (0.6–1.5 GPa) polymer-like coating as the adherent bottom layer and a much harder (8–12 GPa) top layer. The polymer underlayers were grown from 100% octamethylcyclotetrasiloxane (OMCTS) while the hard top layer was either silicon dioxide grown from OMCTS in an oxygen plasma or silicon nitride grown from hexamethyldisiloxane in an ammonia plasma. The bilayer structures combined high surface hardness values with good corrosion resistance, surviving 1800–2600 h in an ASTM B117 salt-fog corrosion test.

High current density ion beam formation from plasma of electron cyclotron resonance discharge

This article describes the research effort to obtain a quality ion beam with high currents from the dense plasma of the pulsed electron cyclotron resonance discharge pumped with high-power millimeter-wave radiation. The results of the experiments aimed at optimization of the two-electrode system for ion extraction are presented. Under the conditions, when the density of the ion current in the vicinity of the plasma electrode was 65–75 mA/cm2, the normalized emittance of the ion beam did not exceed 0.19 π mm mrad.

H − ion production in electron cyclotron resonance driven multicusp volume source

We have used the existing magnetic multicusp configuration of the large volume H− source Camembert III to confine the plasma created by seven elementary multidipolar electron cyclotron resonance (ECR) sources, operating at 2.45 GHz. We varied the pressure from 1 to 4 mTorr, while the total power of the microwave generator was varied between 500 W and 1 kW. We studied the plasma created by this system and measured the various plasma parameters, including the density and temperature of the negative hydrogen ions which are compared to the data obtained in a chamber with elementary ECR sources without multicusp magnetic confinement. The electron temperature is lower than that obtained with similar elementary sources in the absence of the magnetic multicusp field. We found that at pressures in the range from 2 to 4 mTorr and microwave power of up to 1 kW, the electron temperature is optimal for H− ion production (0.6–0.8 eV). This could indicate that the multicusp configuration effectively traps the fast electrons produced by the ECR discharge.

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In the future, LEO spacecraft will be larger and higher powered. Because of the balance of currents through ambient space plasma, their main conductive body will have a higher negative potential without plasma contactor operation. When spacecraft operate with a higher voltage, more intensive arcing is suspected to occur on their surface. In this study, ground-based experiment was carried out to understand the arcing phenomenon and to examine influences of ambient space plasma on the arcing process. Simulating plasmas were generated by electron cyclotron resonance discharge. When arcing occurred on anodized aluminum sample (AAS) plates negatively biased by a capacitor in the plasma environment, the time variations in arc current and bias voltage were measured. Arc spot diameter was also measured. The experimental results showed that both the peak arc current and the total charge emitted by arcing increased with initial charging voltage and neutral particle number density. The diameter of arc spots increased with initial charging voltage although it was almost constant regardless of neutral particle density. Accordingly, high voltage operation of LEO spacecraft might bring drastic degradation of AAS by arcing depending on ambient plasma conditions.

Deposition of hard metal nitride-like coatings in an electron cyclotron resonance discharge

Hard titanium, zirconium and chromium nitride-like coatings were grown in a high-density microwave electron cyclotron resonance discharge. The organometallic deposition precursors were titanium (IV) isopropoxide and tetrakis(dimethylamino)titanium, zirconium 2-methyl-2-butoxide and zirconium t-butoxide, and bis(ethylbenzene)chromium, with ammonia as the reactive gas. The deposited metal nitride-like coatings have nano-indentation hardness values of 20–28 GPa for TiN-like coatings, 17–21 GPa for ZrN-like coatings and 25–31 GPa for CrN-like coatings. Growth rates were 10–20 nm/min. X-Ray photoelectron spectroscopic analyses showed the compositions of titanium-, zirconium- and chromium-containing coatings to be TiC x O y N z , ZrC x O y N z and CrC x O y N z with significant carbon and oxygen atomic concentrations. The titanium nitride-like and zirconium nitride-like coatings had characteristic gold coloring and lasted more than 1000 h in an ASTM B117 salt-fog corrosion test without color change or visible corrosion.

Thermalization of sputtered aluminium atoms in an electron cyclotron resonance plasma source

The transverse temperature of sputtered aluminium atoms in an electron cyclotron resonance discharge has been calculated from the shapes of their Doppler broadening emission lines, which were measured with a pressure scanning Fabry–Perot interferometer. This temperature decreases from 0.8 to 0.28 eV at a distance of 17.5 cm from the Al target when krypton pressure rises from 0.4 to 4 mTorr. For a discharge in argon aluminium temperature falls from 0.5 to 0.18 eV for the same condition.

Development of a hybrid PIG-ECR ion source

A combined ion source with 20 cm beam diameter, utilizing both a cold-cathode Philips or Penning ionization gauge (PIG) discharge and an electron cyclotron resonance (ECR) discharge, has been built and tested. The ion source has been designed to study what effects, if any, might be induced by superimposing microwave power at the ECR condition onto a cold-cathode PIG ion source at low pressures (≤10 −4 Torr). The first experiments with argon gas indicate that the ECR coupling at low pressures results in: (a) transformation of the PIG discharge mode with a dominant anode fall into the hybrid discharge mode with a dominant cathode fall; (b) stabilization of the PIG discharge; and (c) enhanced ion beam output due to increased ionization inside the ion source. The ion beam current is 150 mA (with a beam current density at its axis of 0.35 mA/cm 2), at an anode voltage of 750 V, a microwave power of 200 W and a gas pressure of 0.05 mTorr. The ion source design and the results of preliminary experiments are presented. A stable low-pressure operation mode of the ion source might be promising for broad ion beam production.

Plasma-enhanced deposition of hard silicon nitride-like coatings from hexamethyldisiloxane and ammonia

Hard silicon nitride-like coatings have been grown in a high-density microwave electron cyclotron resonance discharge, using hexamethyldisiloxane (HMDSO) as the deposition precursor and ammonia as the reactive gas. Statistical experiment design methodology was used to investigate the effects of microwave power and NH 3/HMDSO flow-rate ratio on the growth rate, elastic modulus and hardness of the plasma-grown coatings. The films deposited are hard, colorless and transparent, with growth rates of up to 0.5 μm/min. Films lasted 745–840 h in an ASTM B117 salt-fog corrosion test. X-Ray photoelectron spectroscopic analyses showed the coating composition to be SiC x O y N z , with significant carbon and up to 13.7 at.% nitrogen concentration. While not stoichiometric Si 3N 4, coatings grown at high microwave power and high NH 3/HMDSO flow ratios had an elastic modulus of 176 GPa and hardness of 12.2 GPa, comparable to values reported for thermally grown silicon nitride.

Deposition of diamond-like carbon films on inner wall of sub-millimeter diameter steel tube by plasma source ion implantation

Diamond-like carbon (DLC) films were deposited on the inner wall surface of 304 austenitic type stainless steel tubes with inner diameter of 0.9 and 0.5 and 15 mm length by a plasma source ion implantation (PSII). A 2.45 GHz microwave was fed into a tubular vacuum chamber and supplied to an antenna. An acetylene gas was fed into the alumina ceramic tube. Plasma was produced by a coaxial electron cyclotron resonance (ECR) discharge. A magnetic field of one kilogauss was generated by a solenoidal coil. The negative high voltage pulse (typically −10 kV, 1 kHz, 10 μs) was applied to the steel tube. The results showed that the DLC film deposition on the inner wall of sub-millimeter size steel tubes was achieved by the PSII. Raman spectra of the DLC films showed a broad peak related to amorphous carbon structure.

Effect of grid and bias on the characteristic of CHF3 electron cyclot ron resonance discharge plasma

The characteristics of CHF3 electron cyclotron resonance(ECR) plasma, which is formed in the case of a floating grid in an ECR-chemical vapor deposition system and +60V or -60V biased at grid, were investigated by an actinometric optical emission spectroscopy. It is found that the effects of grid and biasing on the distribution of radicals occur mainly at a low microwave input power. It is considered that the distribution of radicals at a low power is controlled by ele ctron collision and sheath potential together due to low electron temperature. H owever, the effect of sheath potential at a high power decreases due to increasi ng electron temperature. As a result, the distribution of radicals at a high pow er is dominated by electron collision.

Study of Wall Recycling and Conditioning on the Hanbit Mirror Device

The wall recycling effect dominantly appears in the ICRH discharge with ω < ωci in the HANBIT plasma. The methods and evaluation of wall conditioning are described. The progress of wall conditioning is monitored with neutral pressure and plasma parameters. Electron cyclotron resonance–discharge cleaning(ECR-DC) is applied to improve wall conditioning, and then electron impact desorption(EID) by filament heating is utilized in order to desorb the impurities from the wall. The impurities are analyzed quantitatively by quadrupole mass spectrometer(QMA). We also install new baking system by Halogen lamp radiation with 2 kW in the HANBIT central cell. It is also observed that Hα emission reduces after lamp heating. The evolution of neutral pressure profiles are carefully evaluated during discharge and monitored discharge cleaning effect after several hundred of radio frequency(rf) shots. The partial pressure of light impurities much reduced after rf discharges The line integrated density and edge density much decreased after rf shots, while edge temperature increases. After ECR-DC, also line density decreases, but edge temperature much increases. Plasma beta goes up more than three times after 250 rf shots.

Ion implantation into inner wall surface of millimeter size diameter steel tube by plasma source ion implantation

Nitrogen and carbon ions were implanted into the inner wall surface of 304 austenitic type stainless steel and Ni tubes with inner diameters of 0.9, 2 and 1.6 mm, by a plasma source ion implantation (PSII). These 30 mm long substrate tubes were fixed to an alumina ceramic tube in a vacuum chamber, fed with nitrogen and acetylene gases. A 2.45 GHz microwave was supplied to an antenna in the alumina ceramic tube and plasma was produced by a coaxial electron cyclotron resonance (ECR) discharge in this tube. A negative high voltage pulse of 15 kV (1 kHz, 10 μs) was applied to the steel and Ni tubes to extract ions from the generated plasma. The compositional and structural characterizations of the implanted surfaces were carried out using Auger electron spectroscopy and Raman spectroscopy. The results showed that uniform nitrogen ion implantation into the millimeter size inner wall surface of metal tubes was achieved by the PSII. Carbon implantation and subsequent diamond like carbon (DLC) coating was confirmed for the inner wall surface treated by acetylene PSII.

Influences of substrate bias on the composition and structure of carbon nitride thin films prepared by ECR-plasma assisted pulsed laser deposition

The influences of substrate bias on the properties of carbon nitride thin films, prepared by plasma assisted pulsed laser deposition, are reported. We demonstrated the feasibility of preparation of carbon nitride thin films containing high nitrogen content. A reactive nitrogen plasma was provided by electron cyclotron resonance (ECR) microwave discharge in nitrogen gas. Target ablation and film preparation were performed in the nitrogen plasma environment, with the growing films being concurrently bombarded by the low-energy nitrogen plasma stream. Rutherford backscattering spectroscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and Raman spectroscopy were used for composition determination and structure analysis. Films consisting homogeneously of carbon and nitrogen were obtained on Si (1 0 0) substrates at low temperatures (<80 °C), with nitrogen content over 50 at.% depending on the bias voltage applied to the substrates. Structural analysis reveals that nitrogen and carbon in the films are bonded through hybridized sp 2 and sp 3 configurations and the prepared films can be considered as a compound containing amorphous carbon phase, N-bonded sp 2 and sp 3 hybridized carbon. Besides the composition dependence on the substrate bias voltage, strong influences of the bias voltage on deposition rate and bonding configuration was also observed. The large amount of highly activated nitrogen species created by ECR discharge is expected to be responsible for efficient nitrogen incorporation, bonding formation and film growth. The subsequent surface reactions promoted by the energetic active nitrogen plasma stream enhance the growth of carbon nitride films, while excessive bombardment of the growing film by the plasma stream with higher energies was observed to decrease nitrogen content and deposition rate due to re-sputtering effect.

Development of new steady-state, low-energy, and high-flux ion beam test device

A new steady-state, low-energy, and high-flux ion beam test device has been developed to study erosion, re-deposition, and hydrogen retention mechanisms of plasma facing materials under high flux conditions. Source plasma was produced by electron cyclotron resonance discharge with 2.45 GHz microwave. Ion extraction was made by spherical multiaperture triode electrodes to obtain high ion flux at the focal point. Ion extraction aperture geometry was designed so that high current density can be obtained in the case of low energy (&amp;lt;500 eV) by applying high deceleration voltage. It was demonstrated that low-energy and high-flux ion beam can be produced by increasing deceleration voltage with the fixed acceleration voltage (beam energy). In the case of hydrogen beam energy of 300 eV, beam power density has rapidly increased with a deceleration voltage over accel–decel ratio 4, and maximum beam flux is 4.1×1020 H/m2 s. On the other hand, maximum beam flux of 3.6×1021 H/m2 s was obtained for 3 keV hydrogen beam. These fluxes are much higher than that of conventional mass analyzed ion beam (&amp;lt;1.0×1020 H/m2 s).

The energy influx during plasma deposition of amorphous hydrogenated carbon films

The integral energy influx from the plasma to the substrate was determined for amorphous hydrogenated carbon (a-C:H) film deposition by magnetron sputtering and in an electron cyclotron resonance (ECR) discharge. The measurements, for which a thermal probe was designed, are based on time evolution of the substrate temperature during the deposition process. The different contributions to the integral energy influx were estimated by model calculations on the basis of assumptions for the kinetic energy of the charge carriers, their recombination, and film condensation. The energy influx during deposition in the CH 4-ECR plasma, which is in the range of 0.5–2 J s −1, is predominantly determined by ions and chemical reactions, while the energy influx in magnetron sputtering, being in the range of 0.2–1.2 J s −1, is mainly determined by fast neutrals and target radiation. The present results emphasise that the energy influx is a key parameter in thin film deposition and is important for comparison and scaling-up of different plasma process systems.

Formation of CN x thin films by reactive pulsed laser deposition assisted by electron cyclotron resonance microwave discharge

Amorphous carbon nitride thin films were synthesized by pulsed laser deposition combined with electron cyclotron resonance (ECR) microwave discharge in nitrogen gas. The ECR discharge supplies active nitrogen species in the deposition environment and to the growing film surface, enhancing the film growth in complex processes accompanied by chemical reaction. The synthesized films were characterized by Rutherford backscattering spectroscopy (RBS), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), and Raman spectroscopy. The films were determined to consist purely of carbon and nitrogen with a nitrogen concentration of 42%, and have a thickness of 550 nm over which carbon and nitrogen are well distributed. Structural characterizations based on XPS, FTIR and Raman analysis showed that these films appear to contain several bonding configurations between carbon and nitrogen with a small amount of C≡N bonds compared with other bonding states.

Low-temperature synthesis of AlN films through electron cyclotron resonance plasma-aided reactive pulsed laser deposition

Combination of pulsed laser ablation with electron cyclotron resonance microwave discharge was demonstrated for a novel method for low-temperature thin film growth. Aluminum nitride thin films were synthesized on silicon substrates at temperatures below 80 °C by means of reactive pulsed laser deposition in nitrogen plasma generated from the electron cyclotron resonance discharge. The synthesized films show a very smooth surface and were found to have a stoichiometric AlN composition. X-ray photoelectron spectroscopy analysis evidenced the formation of aluminum nitride compound. Fourier transform infrared spectroscopy revealed the characteristic phonon modes of AlN. The AlN films were observed to be highly transparent in the visible and near-IR regions and have a sharp absorption edge near 190 nm. The band gap of the synthesized AlN films was determined to be 5.7 eV. The mechanisms responsible for the low-temperature film synthesis are also discussed in the paper. The nitrogen plasma facilitates the nitride formation and enhances the film growth.

Large-volume microwave plasma for energetic H- ionsneutralization

A large-volume microwave electron cyclotron resonance discharge in athree-dimensional multicusp trap can be used for neutralization of fastnegative ions in the ITER neutral beams injection system. The requirements of a plasma neutralizerare discussed. Experiments on the PNX-U installation, constructed for thestudy of plasma confinement in a neutralizer, are described. Improvedpotential confinement of the plasma at the centre of a trap is found. Theimprovement is caused by the formation of the hot electrons on the plasmaperiphery.

Novel Applications of Millimeter and Submillimeter Wave Gyro-Devices

The possible applications of high-power millimeter (mm) and submillimeter waves from gyro-devices span a wide range of technologies. The plasma physics community has already taken advantage of recent advances in applying high-power micro- and mm-waves generated by gyrotron oscillators in the areas of RF-plasma production, heating, noninductive current drive, plasma stabilization and active plasma diagnostics for magnetic confinement thermonuclear fusion research, such as lower hybrid current drive (8 GHz), electron cyclotron resonance heating (ECRH) (28–170 GHz), electron cyclotron current drive (ECCD), collective Thomson scattering and heat-wave propagation experiments. Other important applications of gyrotrons are electron cyclotron resonance (ECR) discharges for generation of multi-charged ions and soft X-rays, as well as industrial materials processing and plasma chemistry. Submillimeter wave gyrotrons are employed in high-frequency broadband electron paramagnetic resonance (EPR) spectroscopy. Future applications which await the development of novel high-power gyro-amplifiers include high resolution radar ranging and imaging in atmospheric and planetary science as well as deep-space and specialized satellite communications and RF drivers for next-generation high-gradient linear accelerators (supercolliders). The present paper reviews the state-of-the-art and future prospects of these recent applications of gyro-devices.

Nitridation of thermal SiO2 films by radio-frequency plasma assisted electron cyclotron resonance: Effect of plasma modes and process parameters

Dual-frequency plasma using electron cyclotron resonance (ECR) and radio-frequency (rf) discharges was used for the nitridation of silicon dioxide (SiO2) films, which were grown by conventional thermal oxidation. Nitridation was performed under ion densities less than 1011 ions/cm3 and substrate temperatures of 300±20 °C. The effects of plasma mode (ECR/dc, ECR/rf, ECR, and rf) and the principal process variables (N2 pressure, ECR power, rf applied voltage, and nitridation time) on formation and growth of the nitrided layer were studied by spectroscopic ellipsometry, Auger electron spectroscopy, and atomic force microscopy. It was observed that the nitrided films were composed of an upper layer of silicon oxynitride (SiOxNy) and an inner layer of SiO2. The plasma mode, N2 pressure, and rf bias affected the reactions and concentration of particles in the gas phase, and therefore impacted growth of the nitrided layer. Plasma parameters and plasma modes were optimized to produce a dense upper nitride layer, while minimizing the effect on the inner SiO2 layer, with the goal of preserving the electronic integrity of the Si–SiO2 interface.