Krzysztof Zdunek

State of impulse plasma in the coaxial generator with continuous gas flow examined by indirect observations

Abstract An attempt was made to reconstruct the behaviour of impulse-generated plasma packets in a coaxial accelerator from the effect of this plasma on the structure of the central anode material and its magnetic properties. Changes in the structure which are evidence of thermal-mechanical processes were studied on a titanium electrode and traces of magnetic fields were investigated using an Alnico alloy electrode. Evidence is presented that initially the plasma moves in the form of a ‘magnetic piston’, and then as a packet with a spiral-like motion around the electrode.

Physical model of dynamic phenomena in impulse plasma coaxial accelerator

Abstract Impulse plasma is used in surface engineering (Impulse Plasma Deposition 1) as an efficient source of mass and energy in the synthesis and deposition of various materials in the form of layers. The plasma is generated and accelerated in a coaxial accelerator. 2,3 In the present work, on the basis of previous studies4 and a snow plow model of the current sheet motion, we propose and discuss a physical model of dynamic phenomena in such device.

Spreading of impulse plasma within a coaxial accelerator

Abstract The paper discusses the mechanism of the generation and spreading of an impulse plasma in a coaxial plasma accelerator. An accelerator of this type utilizes the electrodynamic mechanism of ion acceleration. The existing descriptions of the plasma spreading in a coaxial accelerator are based on the “snow plough” model. This model is not suitable for describing the behaviour of impulse plasma during the impulse plasma deposition synthesis of materials. The present author has found that, in this process, because of the quasi-stationary mode of generation, the impulse plasma soon loses its radial symmetry when spreading within the accelerator. This is an adverse effect. It has been found that it can be reduced by using an external electrode made of a ferromagnetic material.

Distribution of magnetic field in the coaxial accelerator of impulse plasma

The existing descriptions of the plasma spreading in a coaxial accelerator are based on the snow plough model. This model is not suitable for describing the behaviour of impulse plasma during the IPD synthesis of materials. It has been found that, in this process, caused by the quasi-stationary mode of generation, the impulse plasma when spreading within the accelerator, soon loses its radial symmetry. It has also been found that it can be reduced by using the external electrode made of a ferromagnetic material. Present measurements of magnetic field in the accelerator interelectrode space demonstrate a magnetic field distribution dependence on the presence or not of ferromagnetic material in coaxial accelerator construction. The experiments suggest that the use of ferromagnetic material in coaxial accelerator construction reduces harmful deformation (and therefore erosion) of the side surface of the internal electrode.

Reduction of turbulence in an impulse-plasma accelerator operating in a quasi-stayionary mode

Abstract In a conventionally constructed coaxial plasma accelerator operating in a quasi-stationary mode turbulences in plasma flow occur causing deformations of the central anode. By using a ferromagnetic insert an additional magnetic field is generated in the accelerator during plasma flow. As a result, plasma turbulence and consequent wear of the anode are strongly reduced, increasing the technological value of the impulse plasma method. In addition, the source of the vaporized material is confined only to the plane of the central electrode free end.

Combined impulse-stationary impulse plasma deposition

In order to increase the capabilities of the IPD method, we propose supplementing the IPD process with an additional stationary process, namely a glow discharge ignited between the consecutive plasma impulses. In this combined impulse-stationary IPD, the basic transport of mass and energy takes place during the impulse process, whereas the glow discharge process permits the phase (chemical) composition of the growing layer to be controlled. Experiments with TiN as the model material have confirmed the advantages of this combined process. The lattice parameter of TiN produced by the combined technique at various process parameters ranged from 0.422 to 0.425 nm. For comparison, the TiN coatings obtained by the typical IPD method have a lattice constant ranging from 0.421 to 0.423 nm. The useful properties of the coatings produced by the combined technique are now being investigated.

Impulse plasma deposition of aluminum oxide layers for Al2O3/Si, SiC, GaN systems

Abstract Nanocrystalline Al2O3 layers were produced by means of impulse plasma deposition (IPD) technique on Si and SiC substrates. Morphology, microstructure and chemical composition of films and film/substrate interfaces were investigated using SEM and SIMS methods. After depositing on top of the layers metal (Al) dot contacts also C–V and I–V measurements of so produced metal-insulator–semiconductor structures were performed in order to determine their electrophysical properties. Obtained Al2O3 films are uniform, show good adhesion to the substrates and maintain at the same time good stoichiometry and purity. Their electronic properties seem to be promising from the point of view of applications in microelectronics. Features, like low-leakage currents, high resistivity and reproducible C–V and I–V characteristics indicate that IPD aluminum oxide films may be a prospective dielectric material, especially for application in novel wide bandgap materials-based (e.g. SiC) electronic devices.

Snow plow model of IPD discharge

A two-dimensional fluid model of snow plow type to simulate the plasma dynamics in a coaxial accelerator is described. The self-consistent model combines the description of the electric circuit with the plasma resistance and inductance, as well as the balance of magnetic and fluid pressures at the contact interface. The applicability of presented model has been proved by comparison of computational results with the high-speed photographs of plasma dynamics in the impulse plasma deposition (IPD) coaxial accelerator.

Synthesis of Al2O3 condensates from impulse plasma

Abstract The synthesis of Al 2 O 3 condensates was carried out in a coaxial impulse plasma generator. A complex metal—ceramic (Al-Al 2 O 3 ) hot electrode functioned as the source of material. In some selected experiments a ceramic (Al 2 O 3 ) ring was used as an additional source of Al 2 O 3 (or AlO, Al, O) vapour. The impulse plasma was generated by discharging a 100–200 μF capacitor battery charged to a voltage of 3 kV. The plasma gas (O 2 or Ar) pressure was 15–30 Pa. As a result of the impulse plasma process, continuous ceramic coatings were condensed on non-heated Ni substrates. Surprisingly, the monotropic metastable Al 2 O 3 phases were the only phases found in the condenstate material (no stable α-Al 2 O 3 phase and/or Al occured even when argon was used as the plasma gas). This can be explained by the effect exerted by the surface pressure, which was as high as 0.4 GPa.

Novel GIMS technique for deposition of colored Ti/TiO₂ coatings on industrial scale

Abstract The aim of the present paper has been to verify the effectiveness and usefulness of a novel deposition process named GIMS (Gas Injection Magnetron Sputtering) used for the flrst time for deposition of Ti/TiO₂ coatings on large area glass Substrates covered in the condition of industrial scale production. The Ti/TiO₂ coatings were deposited in an industrial System utilizing a set of linear magnetrons with the length of 2400 mm each for covering the 2000 × 3000 mm glasses. Taking into account the speciflc course of the GIMS (multipoint gas injection along the magnetron length) and the scale of the industrial facility, the optical coating uniformity was the most important goal to check. The experiments on Ti/TiO₂ coatings deposited by the use of GIMS were conducted on Substrates in the form of glass plates located at the key points along the magnetrons and intentionally non-heated during any stage of the process. Measurements of the coatings properties showed that the thickness and optical uniformity of the 150 nm thick coatings deposited by GIMS in the industrial facility (the thickness differences on the large plates with 2000 mm width did not exceed 20 nm) is fully acceptable form the point of view of expected applications e.g. for architectural glazing.