P. Zeman

ZrN/Cu nanocomposite film : a novel superhard material

This article reports on the structure and hardness of ZrCu‐N films prepared by dc reactive magnetron sputtering of a ZrCu alloyed target in a mixture of Ar+N 2 using a round planar unbalanced magnetron of diameter 100 mm. It was found that there is a strong correlation between the structure of the film and its hardness. The hard (<40 GPa) ZrCu‐N films are characterized by many weak reflections from poly-oriented ZrN and Cu grains. In contrast, the superhard (µ40 GPa) ZrCu‐N films are characterized by a strong reflection from ZrN grains with a dominate ZrN(111) orientation and no reflections from Cu. The superhard ZrCu‐N films with a hardness of 54 GPa are nc-ZrN/Cu nanocomposite films composed of strongly oriented ZrN grains surrounded by a thin layer of Cu. These films exhibit a high elastic recovery of about 80% (determined by a microhardness tester) and contain approximately 1‐2 wt.% Cu. The superhard nc-ZrN/Cu nanocomposite films represent a new class of superhard materials of the type nc-MeN/metal.

Structure and properties of hard and superhard Zr-Cu-N nanocomposite coatings

Zr‐Cu‐N nanocomposite films represent a new material of the type-nanocrystalline transition metal nitride (nc-MeN):metal. In the present work, films were deposited onto steel substrates using unbalanced dc reactive magnetron sputtering of a Zr‐Cu (62:38 at.%) target. Film structure, chemical composition, mechanical and optical properties were investigated by means of X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, wavelength dispersive electron probe microanalysis, depth-sensing microindentation and spectroscopic ellipsometry. It was found that (i) there is a strong correlation between the film structure, Cu content and film properties and (ii) either hard or superhard Zr‐Cu‐N films can be formed. The superhard coatings with hardness H\ 40 GPa are characterized by a columnar structure, a strong 111 XRD peak from ZrN grains and no diffraction peaks from Cu. These films exhibit a high elastic recovery of about 80% and contain a very low amount of Cu, approximately 1‐2 at.%. In contrast, the hard (B 40 GPa) Zr‐Cu‐N films are characterized by many diffraction peaks from polyoriented ZrN and Cu grains, a more random microstructure and a Cu content higher than 2 at.%. The optical properties of nanocomposite Zr‐Cu‐N films depend on the stoichiometry of the hard ZrNx compound and the content of Cu in the film.

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...

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.

Physical properties and high-temperature oxidation resistance of sputtered Si3N4∕MoNx nanocomposite coatings

This article reports on structure, phase composition and high-T oxidation resistance of sputtered Mo–Si–N films. These films were dc reactively sputtered using an unbalanced magnetron equipped with a MoSi2 alloyed target in a mixture Ar and N2. A continuous increase of partial pressure of nitrogen pN2 from 0to0.6Pa makes it possible to produce two groups of composites: (1) MoSix+a-Si3N4 and (2) a-Si3N4+MoNx. The composites of the first group are crystalline and contain a low amount of the a-Si3N4 phase. On the contrary, the composites of the second group are amorphous and the a-Si3N4 phase dominates in these films. Sputtered films were characterized using XRD, EPMA, microhardness measurements, thermogravimetric measurements and SEM. It was found that the thermal annealing of Mo–Si–N films in flowing air at temperatures Ta⩾900°C results in a loss of the film mass (Δm 1→Mo+N(g) and the formation of volatile MoOx oxides, which diffuse out of film. T...

Hard a-Si3N4/MeNx nanocomposite coatings with high thermal stability and high oxidation resistance

This article reports on a new class of amorphous a-Si3N4/MeNx nanocomposite coatings with a high (≥50 vol.%) content of Si3N4 phase; here Me=Zr, Ta, Mo and W. These nanocomposites exhibit high (>1000°C) thermal stability against crystallization and high (>1000 °C) oxidation resistance if the metal Me incorporated in the nanocomposite is correctly selected. It was found that the Zr-Si-N film deposited on Si(100) substrate exhibits no increase of the mass (m=0) in thermogravimetric measurements performed in flowing air up to 1300 °C, i.e. up to the temperature that is the thermal limit for Si substrate but not for nanocomposite.

Physical and mechanical properties of sputtered Ta–Si–N films with a high (⩾40 at %) content of Si

This article reports on ternary Ta–Si–N films with a high (⩾40 at %) content of Si sputtered from an alloyed TaSi2 target using an unbalanced dc magnetron. The films were deposited under the following conditions: magnetron discharge current Id=1 and 2 A, negative substrate bias Us ranging from Ufl to −500 V, substrate ion current density is=0.5, 0.75, and 1 mA/cm2, substrate temperature Ts ranging from 100 to 750 °C, substrate-to-target distance ds–t=60 mm, partial pressure of nitrogen pN2 ranging from 0 to 0.7 Pa and two values of a total pressure pT=pAr+pN2=0.5 and 0.7 Pa. Main attention is devoted to the investigation of the effect of partial pressure of nitrogen pN2 on mechanical properties of Ta–Si–N films. It was demonstrated that (1) the Ta–Si–N films exhibit an x-ray amorphous structure, (2) all films are electrically conductive but their electrical resistivity increases with increasing Si3N4 content from about 10−5 to about 102 Ω cm, and (3) the hardness H of the Ta–Si–N films is comparable to th...

Hard and superhard nanocomposite Al–Cu–N films prepared by magnetron sputtering

Abstract The article reports on structure, mechanical properties and macrostress of Al–Cu–N films deposited by reactive sputtering using a dc unbalanced magnetron equipped with a round planar aluminum target fixed to the magnetron cathode with a copper ring. A systematic investigation of sputtered films showed that: (i) Al–Cu–N is a new nanocomposite material which can form superhard (>40 GPa) coatings with a maximum microhardness of approximately 48 GPa; (ii) Al–Cu–N can easily form a very fine-grained material; (iii) the size of grains decides on the macrostress in Al–Cu–N films; the Al–Cu–N films composed of grains with the average size of 9.5 nm exhibit a low ( 10 nm) grains exhibit large macrostress of several GPa; and (iv) the macrostress in Al–Cu–N films can be varied from tension to compression by the variation of the energy delivered to the growing film, i.e. by the ion bombardment and the substrate heating. The relationships between microhardness, H, Youngs modulus, E, and elastic recovery, We evaluated from loading/unloading curves measured using the microhardness tester Fisherscope H 100 are also given.

Magnetron sputtered Si–B–C–N films with high oxidation resistance and thermal stability in air at temperatures above 1500 °C

Novel quaternary Si–B–C–N materials are becoming increasingly attractive because of their possible high-temperature and harsh-environment applications. In the present work, amorphous Si–B–C–N films were deposited on Si and SiC substrates by reactive dc magnetron cosputtering using a single C–Si–B or B4C–Si target in nitrogen-argon gas mixtures. A fixed 75% Si fraction in the target erosion areas, a rf induced negative substrate bias voltage of −100 V, a substrate temperature of 350 °C, and a total pressure of 0.5 Pa were used in the depositions. The corresponding discharge and deposition characteristics (such as the ion-to-film-forming particle flux ratio, ion energy per deposited atom, and deposition rate) are presented to understand complex relationships between process parameters and film characteristics. Films deposited under optimized conditions (B4C–Si target, 50% N2+50% Ar gas mixture), possessing a composition (in at. %) Si32–34B9–10C2–4N49–51 with a low (less than 5 at. %) total content of hydrog...

Study of the high-temperature oxidation resistance mechanism of magnetron sputtered Hf7B23Si17C4N45 film

The microstructure evolution and high temperature oxidation mechanism of a hard, amorphous, and optically transparent Hf7B23Si17C4N45 film was studied by x-ray diffraction and transmission electron microscopy. The Hf7B23Si17C4N45 films were deposited by reactive pulse dc magnetron sputtering and annealed in air at temperatures from 1100 to 1500 °C. All annealed films were found to have a two-layered structure composed of the original amorphous and homogeneous layer followed by a nanocomposite oxidized surface layer. The top nanocomposite layer consists of an amorphous SiOx-based matrix and a population of HfO2 nanoparticles with two distinct sublayers. The first sublayer is next to the original amorphous layer and has a dense population of small HfO2 nanoparticles (up to several nanometers) followed by a surface sublayer with coarsened and dispersed HfO2 nanoparticles (up to several tens nm). The HfO2 nanoparticles in the bottom sublayer form by a nucleation and growth process whereas the ones in the surf...