Tick-borne encephalitis (TBE) is peculiar due to its unstable dynamics with profound interannual fluctuations in case numbers – a phenomenon not well understood to date. Possible reasons – apart from ...variable human contact with TBE foci – include external factors, e.g. climatic forcing, autonomous oscillations of the disease system itself, or a combined action of both. Spectral analysis of TBE data from six regions of central Europe (CE) revealed that the ostensibly chaotic dynamics can be explained in terms of four superposed (quasi-)periodical oscillations: a quasi-biennial, triennial, pentennial, and a decadal cycle. These oscillations exhibit a high degree of regularity and synchrony across CE. Nevertheless, some amplitude and phase variations are responsible for regional differences in incidence patterns. In addition, periodic changes occur in the degree of synchrony in the regions: marked in-phase periods alternate with rather off-phase periods. Such a feature in the disease dynamics implies that it arises as basically diverging self-oscillations of local disease systems which, at intervals, receive synchronizing impulses, such as periodic variations in food availability for key hosts driven by external factors. This makes the disease dynamics synchronized over a large area during peaks in the synchronization signal, shifting to asynchrony in the time in between.
CrN films were prepared using three different configurations of the HiPIMS discharge mode and the substrate holder potential. We investigate the effect of a positive pulse voltage (30–400 V) in ...bipolar HiPIMS on the crystal structure, microstructure and resulting mechanical properties of the films, and compare it to the effect of a standard DC bias voltage applied to the substrate holder in unipolar HiPIMS. We find that when the substrate holder is at a floating potential, its charging causes the loss of the plasma-substrate potential difference, necessary for ion acceleration, and no obvious evolution is thus observed with increasing positive pulse voltage. However, when the substrate holder is grounded, the effect of the positive pulse voltage is apparent and different from the effect of the DC bias substrate voltage. That is mainly due to differences in energies delivered into the growing film by bombarding ions. Films prepared using bipolar HiPIMS at a positive pulse voltage of 90 and 120 V exhibit the most interesting properties, namely high hardness (23.5 and 23.1 GPa, respectively) at a relatively low residual compressive stress (1.7 and 1.5 GPa, respectively). The results indicate that as long as the growing film is conductively connected with the ground, bipolar HiPIMS is a suitable method to tailor and improve the film properties.
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•CrN films prepared by bipolar HiPIMS at different positive pulse voltages.•Comparison between a floating and grounded substrate holder in bipolar HiPIMS.•Comparison of the effect of a positive pulse voltage in bipolar HiPIMS and a DC substrate bias voltage in unipolar HiPIMS.•High hardness at relatively low residual stress for CrN films prepared by bipolar HiPIMS.
Binary Zr–Cu thin-film alloys were prepared by non-reactive conventional dc and impulse magnetron co-sputtering using two unbalanced magnetrons equipped with Zr and Cu targets. The magnetron with the ...Zr target was operated in a dc regime while the magnetron with the Cu target in a pulse regime either at low or high density discharge conditions. The elemental composition in the films was controlled in a very wide composition range (∼10–90 at.%). The evolution of the structure, thermal behavior, mechanical, electrical and surface properties of Zr–Cu films with increasing Cu content was systematically investigated. We found that Zr–Cu thin-film metallic glasses were prepared with the Cu content between approximately 30 and 65 at.% Cu independently of the low or high density discharge conditions used. A clear correlation between the evolution of the crystallization temperature and mechanical properties with increasing Cu content was observed. The deposition at the high density discharge conditions resulted in a preparation of the Zr–Cu thin-film metallic alloys with a compressive stress (<0 GPa), an enhanced hardness (>7 GPa), very smooth (surface roughness < 1 nm) and hydrophobic (water contact angle >100°) surface.
•Zr–Cu alloys deposited by magnetron co-sputtering in a wide composition range.•X-ray amorphous films prepared between 18 and 88 at.% Cu.•Metallic glass behavior unambiguously recognized between 30 and 65 at.% Cu.•Correlation of crystallization temperature and mechanical properties observed.•Metallic glasses with enhanced hardness, smooth and hydrophobic surface obtained.
The thermal stability and oxidation behavior of metastable W–Zr thin-film alloys with up to 83 at.% Zr were thoroughly investigated with a focus on the effect of gradual substitution of Zr for W. The ...films were prepared by dc magnetron co-sputtering of W and Zr targets in argon on unheated and unbiased substrates. The experiments showed that a supersaturated α-W(Zr) solid solution structure of as-deposited W-rich films with up to 19 at.% Zr is highly thermally stable up to 1200 °C in argon and the thermal stability of the W–Zr thin-film metallic glasses (33–83 at.% Zr) decreases with increasing Zr content. Nevertheless, the thermal stability of the W–Zr thin-film metallic glass with 33 at.% Zr reaches 1420 °C, which is very high value for binary metallic glass. The annealing of W-rich films (0–24 at.% Zr) in air leads to the formation of a protective surface oxide layer, which serves as a more effective oxygen diffusion barrier due to an increasing packing factor and amorphization with Zr addition. On the other hand, no protective surface oxide layer is grown during the annealing in air in the case of the W–Zr thin-film metallic glasses and the oxidation leads to the formation of compact, homogeneously oxidized substoichiometric W–Zr–O films with an amorphous structure and enhanced mechanical properties before reaching the final mass gain.
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•Metastable magnetron sputtered W–Zr thin-film alloys investigated up to 1500 °C.•Thermal stability of crystalline W-rich films (up to 19 at.% Zr) up to 1200 °C in Ar.•More protective oxide layer formed on W-rich films with Zr addition (≤24 at.% Zr).•Thermal stability of thin-film metallic glass (33 at.% Zr) up to 1420 °C in Ar.•In-volume homogenously oxidized thin-film metallic glasses (33–83 at.% Zr).
•Magnetron sputtered W–Zr thin-film alloys prepared in a very wide composition range.•W-rich films with a single-phase α-W(Zr) solid solution structure up to 24 at.% Zr.•W–Zr metallic glasses with an ...amorphous structure between 33 and 83 at.% Zr.•Zr-rich films with a predominantly dual-phase structure at ≥86 at.% Zr.•Relationships between the structure, microstructure and properties of the films.
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Binary W–Zr thin-film alloys with different metastable structures were prepared by dc magnetron co-sputtering of W and Zr targets in argon atmosphere on unheated and unbiased substrates. The effect of the elemental composition on the formation of different structures and phases was studied in a very wide range of 3–99 at.% Zr. The microstructure and properties of the films were related to the individual metastable structures prepared. We found that W-rich films with an α-W(Zr) solid solution structure can be prepared in much wider range of the elemental composition (up to 24 at.% Zr) than indicated in the equilibrium W–Zr phase diagram. These films exhibited an enhanced hardness (up to 16.1 GPa) and a reduced residual stress (down to −0.05 GPa). Amorphous W–Zr films with a very low surface roughness (down to 0.4 nm) and metallic glass features were prepared with the Zr content between 33 and 83 at.%. The hardness of these films gradually decreased with increasing Zr content due to reducing average bond energy. All films were in the compressive state in contrast to the crystalline ones. The structure of crystalline Zr-rich films with higher than 88 at.% Zr was predominantly dual-phased exhibiting a gradual transition from a metastable β-Zr(W) solid solution (86–96 at.% Zr) through a metastable ω-Zr(W) solid solution (94–100 at.% Zr) to the thermodynamically stable α-Zr phase (99–100 at.% Zr) with increasing Zr (decreasing W) content. We also observed the formation of dual-phase glassy-crystalline structures in the transition zones between fully crystalline and glassy films.
Hard, and optically transparent amorphous Hf6B12Si29Y2C2N45 and Hf5B13Si25Ho3C2N48 films were prepared by reactive pulsed dc magnetron co-sputtering and annealed up to 1500 °C in air. The evolved ...microstructures were studied by X-ray diffraction and transmission electron microscopy to understand the Y- and Ho– doping effects on thermal stability and oxidation behavior. A three-layered microstructure developed in both annealed films. A fully oxidized layer formed at the top surface consisting of cubic fluorite Hf(Y/Ho)O2 nanoparticles embedded in an amorphous SiOx-based matrix. The oxide layer is about 36 % thinner compared to undoped films with similar composition 1. A recrystallized structure formed at the bottom of both films composed mainly of Hf(Y/Ho)N and α-/β-Si3N4. All Hf(Y/Ho)N in the middle layer was oxidized producing vertically oriented Hf(Y/Ho)O2 nanocolumns surrounded by Si3N4 nanocrystalline. The Y- and Ho– doping found to stabilize the cubic fluoride oxide structure and promoted its (1 1 1) columnar texture. The oxidation mechanism of Si3N4 nanodomains occurs via formation of β-SiO2 first followed by its transformation to amorphous SiOx. It is suggested that substitution of Hf4+ with Y3+ and Ho3+ ions within the Hf(Y/Ho)O2 formed an anion vacancy defect structure to preserve charge neutrality affecting the oxidation mechanism in the doped films.
Amorphous quaternary Zr–Hf–Al/Si–Cu thin-film metallic alloys were prepared by non-reactive magnetron co-sputtering using four unbalanced magnetrons equipped with Zr, Hf, Al or Si, and Cu targets. ...The Zr, Hf and Al or Si targets were sputtered in dc regimes while the Cu target in a high-power impulse regime. Two series of films with either Al (up to 17 at.%) or Si (up to 12 at.%) addition were deposited. The effect of the elemental composition on the structure, thermal behavior, mechanical and surface properties, electrical resistivity and oxidation resistance was systematically investigated. All Zr–Hf–Al/Si–Cu films were deposited with an X-ray amorphous structure. The glass transition was, however, recognized only up to 12 at.% Al or 6 at.% Si. The addition of Al or Si enhances mechanical properties of the films and the thermal stability of their amorphous state. This may be explained by an increase of a covalent component of the mixed metallic-covalent bonds with increasing the Al and Si content. Moreover, the Zr–Hf–Al–Cu metallic glasses exhibit a wider super-cooled liquid region, while the Zr–Hf–Si–Cu metallic glasses are more oxidation resistant.
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•X-ray amorphous Zr–Hf–Al/Si–Cu thin-film alloys deposited by magnetron co-sputtering.•Metallic glasses prepared up to 12 at.% Al or 6 at.% Si.•Extension of supercooled liquid region for Zr–Hf–Al–Cu metallic glasses.•Enhancement of hardness, thermal stability and oxidation resistance.•Clear correlation between mechanical properties and thermal behavior.
The outstanding oxidation resistance, thermo-mechanical stability, and chemical inertness of alumina, but also the synthesis of phase pure polymorphs attract particular attention in academia and ...industry. Especially, the difficulties regarding the synthesis of α- or γ-structured Al2O3 by physical vapor deposition techniques are still strong limitations. Within this study, we investigated in detail the influence of 2 at.% tungsten in the Al-target on the process stability and phase formation during reactive DC magnetron sputtering as well as high power impulse magnetron sputtering (HiPIMS) of Al2O3-based coatings. The small addition of W to the Al target allows to increase the oxygen partial pressure by more than 200% while maintaining a stable deposition process. Ion mass spectroscopy measurements yield a promising high fraction of 16O+ and 32O2+, when operating the W-containing target in the metal-to-poisoned transition mode. A significant increase of 16O+ is further provided by the target surface oxide in poisoned mode. Detailed time-of-flight ion mass spectroscopy investigations during one HiPIMS pulse show a clear temporal separation of the individual ions arriving at the substrate plane during the pulse on-time, allowing for controlled ion attraction by synchronizing the bias pulse to the discharge impulse. Equal amounts of 27Al+ and 32O2+ can be attracted using a bias on-time between 400 μs and 900 μs in the “off-time” (after glow) leading to a dense and nano-crystalline coating. Detailed electron microscopy investigations show the presence of metallic phase fractions for higher duty cycles (7.5%). Decreasing the duty cycle to 3.75% leads to amorphous coatings when operating the Al-target at the highest oxygen partial pressure in metallic mode.
•R-HiPIMS deposition of W alloyed Al2O3 coatings to control the poisoning behavior•W alloying increases the oxygen partial pressure by more than 200% before poisoning.•Despite of the target condition (poisoning mode) the Al+/O+ ratio is still above 1.
Time-averaged and time-resolved ion fluxes during reactive HiPIMS deposition of Ti1-xAlxN thin films are thoroughly investigated for the usage of Ti1-xAlx composite targets – Al/(Ti + Al) ratio ...x = 0.4 and 0.6. Ion mass spectroscopy analysis revealed, that increasing x in the target material or reducing the N2 flow-rate ratio leads to a proportional increase of the Al+-ion count fraction, whereas that of Tin+-ions (n = 1, 2) remains unaffected despite of comparable primary ionisation energies between Al and Ti. In fact, energetic Ti2+-ions account for the lowest flux fraction incident on the substrate surface, allowing for a high Al-solubility limit in cubic-structured Ti1-xAlxN thin films (xmax ~ 0.63) at low residual stresses. In addition, time-resolved plasma analysis highlights the simultaneous arrival of metal- and process-gas-ions throughout the entire HiPIMS pulse duration. These ion-bombardment conditions, which were dominated by gas-ion irradiation with a significant contribution of Al+-ions (up to ~20 %) and negligible energetic Ti2+-ions, allowed for the growth of cubic Ti0.37Al0.63N coatings exhibiting high indentation hardness of up to ~36 GPa at a low compressive stress level (σ = −1.3 GPa).
•Mass spectroscopy was used during R-HiPIMS deposition of TiAlN from TiAl targets.•Al+-ions drastically increase with target Al-content & reduced N2-flow rates.•Ti1,2+-ions constitute lowest fraction for all target compositions & N2-flow rates.•Simultaneous arrival of metal & gas-ions during entire HiPIMS pulse.•c-Ti0.37Al0.63N with high hardness (H ~ 36 GPa) & low stress (σ = −1.3 GPa) achieved.
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