S. N. Grigoriev

Broad fast neutral molecule beam sources for industrial-scale beam-assisted deposition

Abstract A new beam-assisted deposition technique is presented featuring fast neutral molecule beams being used instead of conventional ion beams. As compared with ions the neutral beams ensure better treatment stability, reliability, eliminate damages of conductive films with unipolar arcs and substantially reduce the number of beam-induced defects in semiconductors and dielectrics. Fast molecules are being produced as a result of the primary ion beam interaction with slow gas molecules in a charge transfer collision chamber. Acceleration–deceleration of primary ions in two positive space charge layers separated from each other with one accelerating grid allows the beam current density up to 10 mA/cm 2 at any energy of accelerated particles beginning from 10 eV up to several keV. Due to generation of the ion emitter using a cold cathode glow discharge with electrostatic electron confinement, beams of any reactive gas molecules are available. By changing the shape of the accelerating grid and of the electrostatic trap, any beam configurations are available: converging; diverging; or highly coherent beams. Three pilot series of fast molecule sources are developed. Beam cross-section up to 10 4 cm 2 and current up to 10 A lead to industrial-scale beam-assisted deposition at 3×10 −4 –6×10 −3 mbar. Negative biasing of a target immersed in a plasma emitter of the beam source allows utilization of secondary electron emission for energy-effective heating of massive substrates and utilization of the target sputtering for metal vapor production. Both processes are inherently unavoidable but still rarely used by-processes of plasma immersion ion implantation.

Tribological characteristics of (TiZrHfVNbTa)N coatings applied using the vacuum arc deposition method

The effect of the pressure of the nitrogen atmosphere during the formation of vacuum arc nitride coatings based on high entropy alloys of the Ti-Zr-Hf-V-Nb-Ta system on their structure, hardness, and tribotechnical characteristics is considered. It is shown that strong nitride-forming components lead to the dependence of the structural state and properties on the pressure of the nitrogen atmosphere during coating deposition. Deposition at a nitrogen pressure of 0.4 Pa results in the formation of a texture with the [111] axis when the applied bias potential is −70 V and when the bias potential is equal to −150 V the textural structure is biaxial ([111] and [110]) textures and high value of hardness of 51 GPa Along with that the highest value of wear resistance (under oxidizing-mechanical wear) is inherent to coatings formed under the pressure of nitrogen of 0.09 Pa. The strongest microdeformation of coating crystallites corresponds to this pressure.

On the mechanism of encapsulated particle formation during pulsed laser deposition of WSe x thin-film coatings

We have studied factors influencing the formation of particles with the structure of a spherical metal W core inside a WSe2 shell during pulsed laser deposition (PLD) of thin films of tungsten diselenide under variable conditions (buffer gas (Ar) pressure, substrate temperature). It is established that the metal core is formed at the stage of laser ablation of a synthesized WSe2 target, while the shell grows as a result of condensation, migration, and redistribution of atoms during deposition of a laser-initiated atomic flow on the surface of a growing film. Retardation of the atomic flow by a buffer gas at pressures within 2–10 Pa does not ensure activation of the shell condensation process on the metal core in the gas phase. Increasing the substrate temperature from room temperature up to 250°C leads to transformation of the shell structure from amorphous into laminar.

Cutting Tools Nitriding in Plasma Produced by a Fast Neutral Molecule Beam

Nitrogen plasma produced by a broad beam of fast neutral nitrogen molecules in 0.12-m3 vacuum chamber has been studied and used for cutting tools nitriding. The study results prove that fast molecules play a leading role in gas ionization and plasma density is proportional to their energy, equivalent current and gas pressure. Plasma is quite nonuniform: its density is maximal within the beam and rapidly decreases beyond it. Non-self-sustained glow discharge between chamber and an anode immersed in the plasma reduces plasma nonuniformity down to 10%, when discharge voltage amounts to 200–300 V, and raises plasma density by an order of magnitude. After 1-h-long soaking in discharge plasma of isolated from the chamber and heated by 4-keV beam up to 500 °C cutting plates made of high-speed steel their microhardness rises from 950 up to 1400 HV, and the mean radius of cutting edges decreases from 20 to 18 µm.

Equipment for deposition of thin metallic films bombarded by fast argon atoms

Deposition of thin metallic films on dielectric substrates using a source of metal atom flow combined with a flow fast argon atoms has been investigated and the investigation results are presented. The fast atoms are produced due to charge-exchange collisions in a vacuum chamber of argon ions, which are accelerated by potential difference between the hollow-cathode glow-discharge plasma and an emissive grid and enter the chamber through the grid. The metal atoms produced due to ion sputtering of a metallic foil placed on the inner surface of the hollow cathode enter the chamber through the same grid. Substrate pretreatment and pulse-periodic bombardment of the growing film by ∼1-keV argon atoms both ensure adhesion of copper to glass up to 2 × 107 Pa. The use of a hollow substrate holder, whose inner surface is also covered with the same foil, makes it possible to exclude losses of the depositing metal and allows recommendation of the equipment for beam-assisted deposition of precious metal films.

The formation of a hybrid structure from tungsten selenide and oxide plates for a hydrogen-evolution electrocatalyst

It has been found that the pulsed laser deposition of a thin tungsten selenide film, followed by thermal treatment at 550°C in an Ar + O2 mixture of gases, results in the formation of a hybrid structure that is made up of ultrathin WSe2 and WO3–y platelets. The structural and size characteristics of the nanoplatelets deposited on microcrystalline graphite provide the effective hydrogen evolution reaction in a 0.5 M H2SO4 solution, with the cathode current made about seven times higher at a potential of–100 mV and the slope of the Tafel characteristic reduced from 340 to 90 mV/dec.

Formation of thin catalytic WSe x layer on graphite electrodes for activation of hydrogen evolution reaction in aqueous acid

The possibility of obtaining new relatively inexpensive electrode materials to provide enhanced efficiency of hydrogen evolution reaction (HER) in an aqueous acid solution was investigated. For this purpose, the surface properties of cathodes made of microcrystalline graphite were modified by pulsed laser deposition of thin films of WSex. The structure, morphology, and chemical composition of the thin film coatings were varied by changing the deposition conditions and subsequent heat treatment. The compact and dense structure of the film in an amorphous and crystalline state did not result in a marked positive impact on the character of the HER process, which was investigated in 0.5 M H2SO4 solution at room temperature. Formation of thin layers consisting of nanocrystalline “petals” WSe2 caused an increase in cathodic current by more than 6 times (at a voltage of–150 mV), and the Tafel slope of the voltage vs. current curve was reduced by about 80 mV/dec. The conditions were determined to produce on the surface of the graphite cathode a high density of new catalytically active sites that formed on edges of molecular planes forming a layered structure characteristic of WSe2 nanocrystals.

The role of the thermal factor in the wear mechanism of ceramic tools: Part 1. Macrolevel

The developed technique for conducting a multilevel study of the operational characteristics, wear, thermal and stress state of ceramic tools has been described. A correlation between the cutting speed and operational characteristics, as well as the thermal state of the cutters with inserts from nitride ceramics, is revealed. Both peculiarities of the tool wear and the role of the thermal factor in the wear mechanism are determined.

Focused beams of fast neutral atoms in glow discharge plasma

Glow discharge with electrostatic confinement of electrons in a vacuum chamber allows plasma processing of conductive products in a wide pressure range of p = 0.01 – 5 Pa. To assist processing of a small dielectric product with a concentrated on its surface beam of fast neutral atoms, which do not cause charge effects, ions from the discharge plasma are accelerated towards the product and transformed into fast atoms. The beam is produced using a negatively biased cylindrical or a spherical grid immersed in the plasma. Ions accelerated by the grid turn into fast neutral atoms at p > 0.1 Pa due to charge exchange collisions with gas atoms in the space charge sheaths adjoining the grid. The atoms form a diverging neutral beam and a converging beam propagating from the grid in opposite directions. The beam propagating from the concave surface of a 0.24-m-wide cylindrical grid is focused on a target within a 10-mm-wide stripe, and the beam from the 0.24-m-diameter spherical grid is focused within a 10-mm-diame...

A magnetron sputtering device with generation of pulsed beams of high-energy gas atoms

Coating deposition study results are presented a source of joint flow of metal atoms and highenergy gas atoms being used for the deposition. Metal atoms are produced due to sputtering of a flat rectangular target in magnetron discharge. Gas atoms with energies up to 30 keV are produced due to both the acceleration of ions from discharge plasma by high-voltage pulses applied to a grid that is parallel to the target, and ion charge exchange in space-charge sheaths near the grid surface. Metal atoms pass through the grid and are deposited on articles. The coincidence of their trajectories with those of gas atoms that bombard the growing coating allows coatings to be synthesized on dielectric articles that rotate in a chamber. High-energy gas atoms mix the atoms of the coating with the atoms of the article material in its surface layer, thus improving the coating adhesion.