S. V. Rabotkin

Investigation of Plasma Characteristics in an Unbalanced Magnetron Sputtering System

Results are presented from experimental studies of a magnetron sputtering system for different configurations of the magnetic field above the cathode surface. The current-voltage characteristics of a magnetron discharge at different working gas pressures (0.08–0.3 Pa) and currents in the unbalancing coil were studied. The production and transport of charge carriers in a magnetron discharge with an unbalanced magnetic field was investigated by means of probe measurements of plasma characteristics and ion energies in the region between the substrate and the magnetic trap at the cathode surface. The radial distributions of the ion current density, plasma potential, and floating potential in the unbalanced operating mode are found to have pronounced extrema at the magnetron axis. It is shown that the plasma density near the substrate can be increased considerably when the axial magnetic field is high enough to efficiently confine plasma electrons and prevent their escape to the chamber wall.

Hard carbon coatings deposited by pulsed high current magnetron sputtering

Hard (up to 17 GPa) carbon coatings are deposited onto face SiC bearings used in liquid pumps by pulsed high-current magnetron sputtering of graphite. As a result, the friction coefficient is decreased from 0.43 to 0.11 and the wear rate is decreased from 26 to 0.307 μm3 N−1 m−1, which increases the service life of the bearings by approximately three times. The deposited carbon coatings have a high hardness and wear resistance due to the generation of high-density (up to 1013 cm−3) plasma.

Deposition of silicon–carbon coatings from the plasma of a non-self-sustained arc discharge with a heated cathode

Amorphous hydrogenated carbon doped with silicon oxide (a-C:H:Si:O), which is referred to as silicon–carbon coatings in this work, consists of thin amorphous films, which are used as commercial solid lubricants due to their higher stability under extreme environmental conditions as compared to amorphous hydrogenated carbon. The deposition of silicon–carbon coatings from the plasma of a non-self-sustained arc discharge with a heated cathode is considered. Silicon–carbon coatings are deposited using polyphenul methylsiloxane as a precursor at a flow rate of 0.05 mL/min in an argon atmosphere at a pressure of 0.1 Pa. A high-frequency power supply is used to apply a high-frequency bias voltage to a substrate during deposition. After deposition, the mechanical properties of the coatings are studied. The maximum hardness of the coating is 20 GPa at a minimum friction coefficient of 0.16 and a wear rate of 1.3 × 10–5 mm3 N–1 m–1. Energy dispersive analysis shows that the coatings contain a significant content of carbon and oxygen (about 80 and 15%, respectively) and a low content of silicon (about 5%).

Properties of low-emission coatings based on Ag and Cu deposited on polymer film by magnetron sputtering

Results of experiments on the deposition of multilayer low-emission coatings with “oxide-metaloxide” structure on polyethylene terephthalate film by magnetron sputtering are presented. The purpose of this work was to find the composition of coatings which would have high moisture resistance and the possibility to operate outside sealed glass units. For this purpose, coatings with TiO2/ZnO:Ga/Ag/ZnO:Ga/TiO2 and TiO2/Cu/TiO2 structures were proposed and their optical and electrical characteristics were investigated. The optimum thickness of coating layers which provides a good ratio of coating transparency in the visible range with reflection in infrared spectral region was obtained. It was shown that low-emission coatings based on a Ag layer have a higher transparency (82%) and reflection in the infrared region (93%) than coatings based on a Cu layer, for which these characteristics are 60% and 84%, respectively.

Gallium-doped zinc oxide films deposited using an unbalanced magnetron sputtering system

Gallium-doped zinc oxide films are deposited using an unbalanced magnetron sputtering system. The films are deposited by dc sputtering of a conducting ceramic target in an argon atmosphere. The substrate temperature is 150°C. The film surface morphology is studied by scanning electron microscopy and atomic force microscopy. As the degree of magnetron unbalance increases, the electrophysical properties of the films deposited along the system axis are shown to improve, and the distribution of the film electrical resistivity over the substrate surface becomes more uniform.

Solid nanocrystalline fullerite-containing carbon coatings

Solid carbon coatings with a high content of nanocrystalline fullerite have been obtained using unbalanced magnetron sputtering of graphite under conditions of pulsed high-voltage ion bombardment of the film growing on a substrate. It is established that samples possessing the maximum hardness (18.8 GPa) are characterized by maximum values of the volume fraction of fullerite in the coating (50%), coherent scattering domain size (53 nm), degree of preferred grain orientation (85%), relative deformation of the lattice (1.02%), and internal compressive stresses (2.91 GPa). The observed behavior is consistent with the mechanism of strengthening that accounts for the phenomenon of superhardness in nanocrystalline and nanocomposite materials. This assumption is confirmed by the results of investigation of the morphology of growing coatings.

Comparison of characteristics of solid oxide fuel cells with YSZ and CGO film solid electrolytes formed using magnetron sputtering technique

The work describes the methods of manufacturing single cells of solid oxide fuel cell (SOFC) with thin–film YSZ and CGO electrolytes and also with the bilayer YSZ/CGO electrolyte. Formation of YSZ and CGO films on the supporting NiO–YSZ anode of SOFC was carried out using the combined electron–ionic–plasma deposition technique. The microstructure and phase composition of the formed coatings are studied and also comparative analysis of electrochemical characteristics of single fuel cells with different electrolytes is performed. It is shown that the maximum power density of 1.35 W/cm2 at the temperature of 800°C is obtained for the cell with bilayer YSZ/CGO electrolyte. However, the highest performance at lower working temperatures (650–700°C) is characteristic for the fuel cell with single–layer CGO electrolyte; its power density is 600–650 mW/cm2.

Deposition of ultrahard Ti–Si–N coatings by pulsed high-current reactive magnetron sputtering

We report on the results of investigation of properties of ultrahard Ti–Si–N coatings deposited by pulsed high-current magnetron reactive sputtering (discharge pulse voltage is 300–900 V, discharge pulse current is up to 200 A, pulse duration is 10–100 μs, and pulse repetition rate is 20–2000 Hz). It is shown that for a short sputtering pulse (25 μs) and a high discharge current (160 A), the films exhibit high hardness (66 GPa), wear resistance, better adhesion, and a lower sliding friction coefficient. The reason is an enhancement of ion bombardment of the growing coating due to higher plasma density in the substrate region (1013 cm–3) and a manifold increase in the degree of ionization of the plasma with increasing peak discharge current (mainly due to the material being sputtered).

Features of the modification of microstructure and properties for copper-doped titanium nitride coatings

Features of a defective microstructure and the mechanical properties of titanium nitride coatings having different copper content are investigated by means of transmission electron microscopy, X-ray structural analysis, microhardness measurement, and scratch tests. It is shown that, under a relatively low deposition temperature and ion-induced surface activation during the growth of a TiN-Cu coating, a highly defective single-phase crystalline state of titanium nitride is formed at a copper concentration of up to 12 at %. The noted state is characterized by a scale hierarchy of the lattice fragmentation from sizes of ∼10–15 to 100 nm, high bending-torsion of the crystal lattice (tens of degrees per micron), and a level of local internal stresses from ∼E/40 to ∼E/120 (E is the modulus of elasticity). The revealed high gradients, including those of a dipole character, for the bending-torsion on characteristic scales up to some tens of nanometers can be described within the framework of a model for the continuous distribution of dislocation-disclination ensembles. The effect of the copper content on an increase in the degree of dispersion of the subgrained structure, a decrease in the local bending-torsion of the crystal lattice within subgrains, the level of local internal stresses, and variation of the hardness and strength in scratch tests is revealed.