K. V. Oskomov

Optical studies of plasma inhomogeneities in a high-current pulsed magnetron discharge

Results are presented for experimental studies of the plasma glow in a high-current pulsed magnetron discharge by using a high-speed optical frame camera. It is found that the discharge plasma is inhomogeneous in the azimuthal direction. The plasma bunches rotate with a linear velocity of ∼1 cm/μs in the direction of electron Hall drift, and their number is proportional to the discharge current. Plasma inhomogeneities in the form of plasma jets propagate in the form of plasma jets from the cathode region toward the anode. It is shown analytically that the formation of inhomogeneities is caused by the necessity to transfer high-density electron current across the magnetic field.

a-C:H films deposited in the plasma of barrier and surface discharges at atmospheric pressure

The aim of this work is the synthesis of the diamond-like coatings in a barrier and surface discharges at the atmospheric pressure and the investigation of their properties. The best characteristics had the coatings obtained from methane (the ratio of hydrogen atoms to carbon atoms is H/C=1.04, the ratio of the diamond-like and graphite-like C-C bonds sp 3 :sp 2 100%:0%) and from the acetylene and hydrogen mixture (1:19) (H/C=0.73, sp 3 :sp 2 = 68%:32%) in barrier discharge, as well as from methane in surface discharge (H/C =0.69-1.03, sp 3 :sp 2 =78%:22%). By their chemical and phase composition these coatings are close to the diamond-like hydrogenated (a-C:H) films obtained by traditional methods of plasma assisted chemical vapor deposition at low pressure (<10 Torr). At the same time proposed methods for fast deposition of a-C:H films make this process less expensive compared to the conventional techniques, which implies that the field of application of these films can be widened substantially.

Ion-assisted pulsed magnetron sputtering deposition of ta-C films

Abstract The process of ion-assisted deposition of ta-C films by pulsed magnetron sputtering of a graphite target has been investigated. Probe measurements of the magnetron discharge plasma have been performed and its space- and time-dependent characteristics have been obtained as functions of the sputtering parameters and the bias voltage applied to the substrate. It has been shown that the density of the pulsed magnetron discharge plasma approaches values typical of pulsed laser or vacuum arc cathode sputtering of graphite (1017−1018 m−3). Raman scattering was used to examine the ta-C films produced at both low and high pulsed bias voltages applied to the substrate (Usub

Specific features of the determination of the mechanical characteristics of thin films by the nanoindentation technique

The hardness and the elastic modulus of Cu thin films on Si, Ti, Cu, and Al substrates are investigated. It is demonstrated that the use of the Oliver-Pharr method in combination with the technique for evaluating the true hardness makes it possible to determine uniquely the hardness of Cu thin films at different ratios between the hardnesses of the film and the substrate. The elastic modulus of thin films can be correctly measured by the Oliver-Pharr method only in the case where the film and the substrate exhibit identical elastic properties. In order to determine the elastic moduli of films with the use of the parameter P/S2, the film and the substrate should have close values of both the hardness and the elastic modulus.

Properties of diamondlike films obtained in a barrier discharge at atmospheric pressure

Diamondlike films are synthesized from gaseous hydrocarbons in a barrier discharge at atmospheric pressure. The films were investigated using transmission electron microscopy, electron diffraction, and infrared spectroscopy. A technique for determining the quantitative characteristics of the films (hydrogen content, ratio of different types of carbon-carbon bonds and hydrocarbon groups) using standard samples is described. The highest-quality films were obtained from methane (ratio of hydrogen to carbon atoms H/C=1.04, fraction of diamondlike to graphitelike bonds sp3: sp2=100%: 0%) and from a mixture of acetylene and hydrogen in the ratio 1:19 (H/C=0.73, sp3: sp2=68%: 32%).

Deposition of highly adhesive amorphous carbon films with the use of preliminary plasma-immersion ion implantation

Abstract The usability of the following two types of plasma generators for deposition of highly adhesive a-C:H films on the large area substrates has been studied: (1) a source of plasma generated by means of a non-self-sustained arc discharge in low-pressure gas; and (2) an ion-plasma source on the basis of a Hall current accelerator with closed electron drift. The distinctive features of both sources are: (a) the possibility of the generation of extended flows (up to 2 m) of relatively dense plasma (∼10 10 cm −3 ); and (b) control of the plasma ionization degree, allowing realization of both preliminary plasma-immersion ion implantation (PIII) of a substrate and subsequent plasma-immersion ion-assisted deposition (PIID) of a-C:H film. The results of experimental investigations into the characteristics of the sources in different operational regimes are presented. Taking into account the probe measurements of plasma parameters, both generators have been optimized to operate in the PIII and PIID regimes. Characteristics of the pulsed negative bias applied to the substrate in both regimes have also been determined. It was shown that both sources allowed deposition of a diamond-like film on large-area substrates with a growth rate of 100–300 nm h −1 . A hard (20–30 GPa) a-C:H coating containing approximately 60% of carbon atoms with sp 3 hybridization and having satisfactory adhesion to the substrate can be obtained if short (∼60 μs) high-voltage (∼6 kV) bias pulses are applied to the substrate.

Use of the hydrocarbon plasma of a low-pressure arc discharge for deposition of highly adhesive a-C:H films

Abstract It has been investigated whether a source of a hydrocarbon plasma generated by a non-self-sustained low-pressure arc discharge is suitable for production of highly adhesive a-C:H films. The distinguishing feature of this plasma source is the possibility for varying the degree of plasma ionization and the degree of destruction of hydrocarbon gases, making possible to realize both pure plasma-immersion ion implantation (PIII) and plasma-immersion ion deposition (PIID) in a unified vacuum cycle. The plasma parameters were measured with probes as functions of discharge current. Based on these measurements, the parameters of plasma generator have been determined for the PIII and PIID operation. The parameters of the pulsed bias voltage applied to the substrate in the process of the ion implantation and growth of an a-C:H film have also been preliminary chosen. For PIID it has been demonstrated that the improvements in quality of the a-C:H coating and in its adherence to the substrate are attained when an energy per carbon atom built in the coating is lying in the range 200–500 eV. The growth rates of a-C:H films in this case are approximately 200–300 nm/h. It was shown that the most favorable for achieving high energies per deposited carbon atom and for reducing of residual intrinsic stress are short (∼60 μs) high-voltage (>1 kV) substrate bias pulses.

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.

Study of the plasma parameters in a high-current pulsed magnetron sputtering system

Results are presented from experimental studies of the current-voltage characteristics and spatial and temporal parameters of the plasma in a high-current pulsed magnetron sputtering system with a 10-cm-diameter plane disk cathode. It is shown that the plasma density in such a system is three orders of magnitude higher than that in conventional dc magnetron discharges and reaches 1013 cm−3 at a distance of 250 mm from the cathode at a peak discharge current of 500 A. The plasma propagates from the cathode region at a velocity of 1 cm/μs in the axial direction and 0.25 cm/μs in the radial direction. Optical emission spectroscopy shows that the degree of plasma ionization increases severalfold with increasing discharge current, mainly at the expense of the sputtered material.

Properties of multilayer ZnO:Ga/Ag/ZnO:Ga coatings applied by magnetron sputtering

The methods of van der Pau, spectrometry, and atomic force microscopy were used to study the optical and electrophysical properties of multilayer ZnO:Ga/Ag/ZnO:Ga coatings applied by magnetron sputtering. The effect of the thickness of the coating layer was studied with respect to the surface resistance, transparency, and reflection of the multilayer structure in the visible and infrared wavelength ranges. The coating surface morphology and moisture resistance was studied. The ZnO:Ga/Ag/ZnO:Ga coatings were shown to have a high transparency (T = 90%) in the visible range, high reflection coefficient in the IR range (R = 93%), and low surface resistance (Rs = 4.88 Ohm/sq). The moisture resistance studies showed the highest moisture resistance of ZnO:Ga (25 nm) / Ag (15 nm) / ZnO:Ga (75 nm) coatings, which are not changed by testing and can be used for the effective protection of silver films against degradation.