J. Vlček

Magnetron sputtering of hard nanocomposite coatings and their properties

The article reports on the present status of knowledge in the field of hard and superhard nanocomposite coatings prepared by magnetron sputtering. Special attention is devoted to the two-phase nanocomposites composed of one hard and one soft phase. Trends of the next development are outlined.

Collisional-radiative model for an argon glow discharge

An extensive collisional-radiative model for the argon atoms in a glow discharge has been developed. Sixty-five effective argon atomic levels are considered. The processes taken into account are radiative decay, electron, fast argon ion and argon atom and thermal argon atom impact ionization, excitation and deexcitation between all the levels, electron-ion radiative recombination, and electron-ion three-body recombination where the third body is an electron, fast argon ion or atom, or a thermal argon atom. Some additional processes are incorporated for the two 4s metastable levels, i.e., Penning ionization of sputtered atoms, two- and three-body collisions with argon ground state atoms, collisions between two atoms in a metastable level, and diffusion and subsequent deexcitation at the walls. Typical results of the model are the populations of the various excited levels as a function of distance, and the relative contributions of different populating and depopulating processes for all levels.

Mechanical and optical properties of hard SiCN coatings prepared by PECVD

Novel amorphous SiCN coatings are becoming increasingly attractive because of their mechanical, optical and electronic properties. In the present work, SiCN films were fabricated by PECVD from SiH4/CH4/N2/Ar gas mixtures at a temperature of 400 °C. Mechanical properties such as hardness, Youngs modulus, friction coefficient and stress were evaluated, respectively, by depth-sensing indentation, pin-on-disk, micro-scratch and curvature methods. Films deposited under optimized conditions exhibited a hardness >30 GPa, Youngs modulus >190 GPa, elastic rebound of 85% and a compressive stress of approximately 1 GPa. A friction coefficient against Al2O3, ranging from 0.75 to 0.25 and a low surface roughness of approximately 1 nm were found to be accompanied by a refractive index ranging from 1.85 to 2.10 (at 550 nm) and an extinction coefficient between 1.0×10−4 and 4.5×10−2. The film behavior is correlated with the microstructure and composition determined by SEM, XPS, AFM and broad-range UV–VIS–NIR–IR spectroscopic ellipsometry.

Tribological study of CNx films prepared by reactive d.c. magnetron sputtering

Abstract The effects of both substrate bias voltage during fabrication and countersurface materials during sliding, on the tribology of CN, films are reported. Amorphous CN, films (12–24 at.% N), about 1 μm thick, were deposited onto Si(100) substrates at 600°C by d.c. magnetron sputtering of graphite in a nitrogen plasma. Tribological behaviour of the CN x films was evaluated in continuous, unidirectional sliding against different materials (Al 2 O 3 , 52100 steel, and diamond film-coated Si 3 N 4 balls) in pin-on-disk tests. Low friction coefficient values (μ = 0.1–0.25) were found for soft, but rougher, films prepared at lower bias voltage (−300 V). Such films exhibited a relatively high wear rate (≥ 1.3 × 10 −13 m 3 N −1 m −1 ), partial transfer to the alumina ball, but the wear debris acted as a lubricant during sliding. Harder CN x films prepared at higher bias voltage (−700 V) resulted in lower wear but higher friction levels (μ = 0.25–0.5) when sliding against alumina. The hardest film (23 GPa) prepared at a pressure of 0.5 Pa also showed lower wear, but relatively high and variable friction, behaviour when sliding against 52100 steel (μ = 0.4–0.5). Sliding against the rough, polycrystalline diamond coated countersurface eventually led to film delamination. Friction coefficients calculated from scratch test measurements are also compared with previous results obtained for diamond-like carbon films.

Reactive magnetron sputtering of hard Si-B-C-N films with a high-temperature oxidation resistance

Based on the results obtained for C–N and Si–C–N films, a systematic investigation of reactive magnetron sputtering of hard quaternary Si–B–C–N materials has been carried out. The Si–B–C–N films were deposited on p-type Si(100) substrates by dc magnetron co-sputtering using a single C–Si–B target (at a fixed 20% boron fraction in the target erosion area) in nitrogen-argon gas mixtures. Elemental compositions of the films, their surface bonding structure and mechanical properties, together with their oxidation resistance in air, were controlled by the Si fraction (5–75%) in the magnetron target erosion area, the Ar fraction (0–75%) in the gas mixture, the rf induced negative substrate bias voltage (from a floating potential to −500V) and the substrate temperature (180–350°C). The total pressure and the discharge current on the magnetron target were held constant at 0.5Pa and 1A, respectively. The energy and flux of ions bombarding the growing films were determined on the basis of the discharge characterist...

High-power pulsed sputtering using a magnetron with enhanced plasma confinement

High-power pulsed dc magnetron discharges for ionized high-rate sputtering of metallic films were systematically investigated. The depositions were performed using two unbalanced circular magnetrons of different types with a directly water-cooled planar copper target of 100mm in diameter. The repetition frequency was 1kHz at a fixed 20% duty cycle and an argon pressure of 0.5Pa. Time evolutions of the discharge characteristics were measured to provide information on absorption of energy in the discharge plasma and on transfer of arising ions to the substrate at a target power density in a pulse up to 950W∕cm2. Time-averaged mass spectroscopy was performed at the substrate position to characterize ion energy distributions and composition of total ion fluxes onto the substrate. The deposition rate of the copper films formed on a floating substrate at the distance of 100mm from the target was 2.2μm∕min at an average target power density over a pulse period of 96W∕cm2. Very effective ionization of sputtered c...

Reactive magnetron sputtering of CNx films: Ion bombardment effects and process characterization using optical emission spectroscopy

CNx films were deposited on Si(100) substrates at a substrate temperature of 600 °C using dc magnetron sputtering of a high-purity graphite target in pure nitrogen. The film characteristics were primarily controlled by the pressure, p, (0.05–5 Pa), the discharge current on the magnetron target, Im, (0.5–3 A), and the rf induced negative substrate bias voltage, Ub, (−300 to −1200 V). The films, typically 1–2 μm thick, were found to be amorphous, and they possessed the N/C atomic concentration ratio up to 0.35, the hardness up to 40 GPa, the elastic recovery up to 85%, and good adhesion and promising tribological properties. The energy and flux of ions bombarding the target and the growing films were evaluated on the basis of the discharge characteristics measured for both the dc magnetron discharge and the rf discharge in the deposition zone. Optical emission spectroscopy was used to study the behavior of significant atomic and molecular species, such as N, N2, N+, N2+, CN, C, and C2, near the substrate an...

Ion flux characteristics in high-power pulsed magnetron sputtering discharges

High-power pulsed dc magnetron discharges for ionized high-rate sputtering of copper films were investigated. The repetition frequency was 1 kHz at a fixed 20% duty cycle and argon pressures of 0.5 Pa and 5 Pa. Time evolutions of the discharge characteristics were measured at a target power density in a pulse up to 950 W/cm2. Time-averaged mass spectroscopy was performed at substrate positions. It was shown that copper ions are strongly dominant (up to 92%) in total ion fluxes onto the substrate. Their energy distributions with a broadened low-energy part at a lower pressure are extended to higher energies (up to 45 eV relative to ground potential for the target-to-substrate distance of 100 mm).

Hard amorphous nanocomposite coatings with oxidation resistance above 1000°C

Abstract This article reports on two classes of novel hard amorphous coatings: (a) Si3N4/MeNx coatings with high (≥50 vol.-%) content of Si3N4 phase; here Me=Zr, Ta, Ti, Mo, W, etc. and x=N/Me is the stoichiometry of MeNx metal nitride phase, and (b) Si–B–C–N coatings with strong covalent bonds. These nanocomposites exhibit high thermal stability against crystallisation and high oxidation resistance, both at temperatures considerably exceeding 1000°C. Hard amorphous coatings were prepared using reactive magnetron sputtering. Properties of sputtered coatings were characterised using the following techniques: X-ray diffraction, electron probe microanalysis, Rutherford backscattering spectrometry, elastic recoil detection, high resolution transmission electron microscopy, selected area electron diffraction, atomic force microscopy, microhardness tester Fischerscope H 100, differential scanning calorimetry and thermogravimetric analysis. It was found that hard amorphous coatings of both new systems exhibit excellent oxidation resistance at high temperatures about 1500 and 1700°C for amorphous Si3N4/MeNx and Si–B–C–N coatings respectively.

Pulsed dc magnetron discharge for high-rate sputtering of thin films

This article analyzes a pulsed magnetron discharge. Main attention is devoted to the specific behavior of the pulsed discharge. The time development of pulsed discharge is composed of three regimes of operation: (1) plasma buildup, (2) stationary plasma, and (3) decaying plasma when the pulse power is off. The duration of individual regimes strongly depends on the pulse length t1, the repetition frequency fr of pulses, the power delivered into the discharge, and the operating pressure. The proportion of duration of the regime of plasma buildup to the regime of stationary plasma in the pulse dramatically influences the I–V characteristics of the pulsed discharge and the deposition rate of sputtered films. The I–V characteristics of an unbalanced round planar magnetron with a Cu target 100 mm in diameter are shown. The deposition rate of Cu films sputtered with the pulsed magnetron is also given.