Hollow cathode discharges (HCD) are capable of generating dense plasmas and have been used for development of high-rate, low-pressure, high-efficiency processing machines. The geometric feature of a HCD promotes oscillations of hot electrons inside the cathode, thereby enhancing ionization, ion bombardment of inner walls and other subsequent processes. At the same power the hollow cathode exhibits plasma density one to two orders of magnitude higher than that of conventional planar electrodes. The aim of the present studies was to obtain experimental observations about the main features of a dc hollow cathode discharge in order to evaluate its capability of generating compounds in the plasma medium, by reaction between sputtered species from the cathode and radicals from the gas discharge. Especial interest is focused on aluminum nitride (AlN) formation which is very desirable if a deposition of thin film of this material is concerned. Plasma properties were inferred from the current-voltage characteristics of a single Langmuir probe positioned at the inter-cathode space. Through mass spectrometry technique some species in the plasma gas phase could be monitored for various operating conditions of the discharge. This mass analysis together with the probe measurements gives guidance for optimization of AlN generation in the discharge consequently for deposition of thin films of this material.
The paper is devoted to the proof of the uniqueness theorem for solution of the equation for the non-local ionization source in a glow discharge and a hollow cathode in general 3D geometry. The theorem is applied to wide class of electric field configurations, and to the walls of discharge volume, which have a property of incomplete absorption of the electrons. Cathode is regarded as interior singular source, which is placed arbitrarily close to the wall. The existence of solution is considered also. During the proof of the theorem many of useful structure formulae are obtained. Elements of th…
General form of the non-local equation for an ionization source in glow discharge and hollow cathode 3D-simulation is formulated. It is a fundamental equation in a hollow cathode theory, which allows to make up a complete set of field equations for a self-consistent problem in a stationary glow discharge and a hollow cathode. It enables to describe adequately the region of negative glow and the hollow cathode effect. Here you can see first attempts to compare calculation results of electrical dependences (pressure - voltage) and experimental data, - under conditions of gradual appearance of th…
A new approach for solving the problem of creation of inverse electron distribution function and practical recommendations for experimental searches for such media in glow discharges with hollow and flat cathodes
Micro hollow cathode discharges (MHCD) were produced using 250 m thick dielectric layer of alumina sandwiched between two nickel electrodes of 8 m thickness. A through cavity at the center of the chip was formed by laser drilling technique. MHCD with a diameter of few hundreds of micrometers allowed us to generate direct current discharges in helium at up to atmospheric pressure. A slowly varying ramped voltage generator was used to study the ignition and the extinction periods of the microdischarges. The analysis was performed by using electrical characterisation of the V-I behaviour and the …
The results from a series of experiments are presented whose purpose is to explore different schemes which may lead to the formation of pure metal plasmas in a capillary discharge with parameters appropriate for X ray lasing. The experiments were performed in ceramic wall capillary discharges at currents of up to 120 kA, with an available ID of between 3 and 8 mm and with lengths from 60 to 100 mm. Initial plasma conditions in the capillary exploit transient hollow cathode effects in a preionizing discharge. A laser focussed onto the back surface of the cathode initiates both beam activity in …
To simulate the influence of pendulum effect in hollow cathode configuration on a current-voltage characteristic it is proposed to consider a plane glow discharge in one-dimensional space configuration with two plane parallel cathodes and one plane anode in the middle. A pendulum effect could be switched on or off, with consideration for the anode to be transparent or not for fast ionizing electrons. On the basis of a stationary kinetic equation for ionizing electrons an integral equation for a source of ionization is derived. This equation can be used as a component in self-consistent problem…
The electron sheath formation in a DC magnetised plasma of modified hollow cathode source is studied. The discharge consists of two plane parallel cathodes and a small cubical anode placed off axis at the center. The argon plasma is produced and the properties of the plasma in response to the sheath formation near the anode are studied using electrical and optical diagnostics. In particular, the effect of pressure, magnetic field on discharge parameters such as discharge current, plasma potential, plasma density and electron temperature is studied. The discharge showed an onset of anode glow a…
Large-amplitude current-driven instabilities in hollow cathode plumes can generate energetic ions responsible for cathode sputtering and spacecraft degradation. A 2D2V (two dimensions each in configuration [D] and velocity [V] spaces) grid-based Vlasov--Poisson (direct kinetic) solver is used to study their growth and saturation, which comprises four stages: linear growth, quasilinear resonance, nonlinear fill-in, and saturated turbulence. The linear modal growth rate, nonlinear saturation process, and ion velocity and energy distribution features in the turbulent regime are analyzed. Backstre…
In this work, we demonstrate a new method to produce black TiO2 from pristine anatase TiO2 films. It consists on the immersion of TiO2 films in a hollow cathode H2 RF plasma for a few minutes, resulting in an efficient blackening of TiO2. In this study, the pristine anatase TiO2 films were grown by magnetron sputtering onto cover glass and c-Si substrates and then annealed at 450 °C for 2 h. Before and after the hollow cathode H2 plasma treatment, the samples were characterized by profilometry, UV-Vis spectrophotometry, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, f…
Continuous wavelet transform (CWT) based time-scale and multi-fractal analyses have been carried out on the anode glow related nonlinear floating potential fluctuations in a hollow cathode glow discharge plasma. CWT has been used to obtain the contour and ridge plots. Scale shift (or inversely frequency shift) which is a typical nonlinear behaviour, has been detected from the undulating contours. From the ridge plots, we have identified the presence of nonlinearity and degree of chaoticity. Using the wavelet transform modulus maxima technique we have obtained the multi-fractal spectrum for the…
Proof of operation of a micro-hollow cathode discharge driven by a true ns-pulsed high voltage: emission properties and atomic nitrogen production
Laboratoire des Sciences des Procédés et des Matériaux (LSPM), CNRS, Université Sorbonne Paris Nord（材料过程与科学实验室，法国国家科学研究中心，索邦巴黎北大学）；Laboratoire Energétique Moléculaire et Macroscopique, Combustion (EM2C), CNRS, Université Paris Saclay（分子与宏观能量、燃烧实验室，法国国家科学研究中心，巴黎萨克雷大学）
This paper presents the application of two classical models to high-resolution electric field measurements carried out in a hollow cathode discharge operated in pure hydrogen plasma. The electric field determination has been done via the Stark shifting and splitting of the 2S level of hydrogen, followed by optogalvanic detection. Two classical models, Rickards' and Wro{ń}ski's, are applied to these measurements with the objective of obtaining a first estimation on the discharge dynamics. The chosen models provide an idea of the ions movement, their energy and their mean free path at the cathod…
Parallel Micro Hollow Cathodes Discharges are characterised by electrical and spectroscopic studies and by using an ICCD camera. V-I curves present a hysteresis cycle between Townsend and normal glow regimes. For I d =4-10mA, gas temperature ranges between 300-500{\textdegree}C. When the diameter of a hole decreases, a more significant discharge voltage is needed.
Results are presented that have been obtained while operating the graphite hollow cathode duoplasmatron ion source in dual mode under constant discharge current. This dual mode operation enabled us to obtain the mass and emission spectra simultaneously. In mass spectra C3 is the main feature but C4 and C5 are also prominent, whereas in emission spectra C2 is also there and its presence shows that it is in an excited state rather than in an ionic state. These facts provide evidence that C3 is produced due to the regeneration of a soot forming sequence and leave it in ionic state. C3 is a stable…
The high density of RF-DC plasma N2-H2 was used to make precise micro-texturing onto AISI420 has complex textured geometry. The original 2D micro-patterns were drawn onto substrate surface by maskless patterning using by of nano-carbon ink. These micro-patterned specimens were further plasma-nitrided at 673 K for 5.4 ks by 70 Pa using the hollow cathode device. The emissive light spectroscopy shows species in plasma were nitrogen atoms together with NH radicals and nitrogen molecular ions. Unprinted surface areas had selectively nitrided, have high nitrogen solute contents up to 12 mass%. Mask…
