Bernhard Sartory

Oxidation of arc-evaporated Al1−xCrxN coatings

The recently introduced Al1−xCrxN coatings are characterized by superior thermal stability and oxidation resistance. Although several studies on the microstructure and mechanical properties of these coatings have been published, the oxidation behavior and mechanisms were only investigated for Al1−xCrxN with Cr∕Al ratio bigger than 1. Within this work, the oxidation of arc-evaporated Al1−xCrxN coatings was investigated as a function of the Al content. Coatings were deposited onto cemented carbide substrates using an industrial-scale arc evaporation system (Balzers rapid coating system) and alloyed Al∕Cr targets yielding Al1−xCrxN coatings ranging from x=0.29 to x=0.79. Heat treatments in air were conducted in the temperature range between 900 and 1100°C. For comparison, samples were also annealed in Ar between 900 and 1200°C. Elemental distributions within the coating and the oxide layers were determined by secondary ion mass spectroscopy. After annealing in Ar, Cr was found to segregate to the coating sur...

In-situ Observation of Cross-Sectional Microstructural Changes and Stress Distributions in Fracturing TiN Thin Film during Nanoindentation

Load-displacement curves measured during indentation experiments on thin films depend on non-homogeneous intrinsic film microstructure and residual stress gradients as well as on their changes during indenter penetration into the material. To date, microstructural changes and local stress concentrations resulting in plastic deformation and fracture were quantified exclusively using numerical models which suffer from poor knowledge of size dependent material properties and the unknown intrinsic gradients. Here, we report the first in-situ characterization of microstructural changes and multi-axial stress distributions in a wedge-indented 9 μm thick nanocrystalline TiN film volume performed using synchrotron cross-sectional X-ray nanodiffraction. During the indentation, needle-like TiN crystallites are tilted up to 15 degrees away from the indenter axis in the imprint area and strongly anisotropic diffraction peak broadening indicates strain variation within the X-ray nanoprobe caused by gradients of giant compressive stresses. The morphology of the multiaxial stress distributions with local concentrations up to −16.5 GPa correlate well with the observed fracture modes. The crack growth is influenced decisively by the film microstructure, especially by the micro- and nano-scopic interfaces. This novel experimental approach offers the capability to interpret indentation response and indenter imprint morphology of small graded nanostructured features.

Oxidation and diffusion processes during annealing of AlCrVN hard coatings

V-alloyed AlCrN hard coatings were deposited by reactive arc evaporation in an industrial-sized deposition system and subsequently annealed in ambient air at temperatures ranging from 550to700°C in order to study the formation mechanisms of the desired lubricious oxides. The oxidized samples were investigated by means of secondary ion mass spectrometry depth profiling, x-ray diffraction, Raman spectroscopy, and analytical transmission electron microscopy. Vanadium diffusion in the oxidized part of the coating leads to the formation of a V-rich top layer containing AlVO4 and the desired lubricious oxide V2O5 followed by a V-depleted inner oxide layer consisting of a mixed or nanocrystalline (Al,Cr,V)2O3 on top of the intact AlCrVN coating.

Mechanical property enhancement in laminates through control of morphology and crystal orientation

This article shows the successful implementation of biological design principles into synthetic laminate materials in order to enhance their mechanical properties. We demonstrate and provide a strategy for laminate thin films, which reveals that the control of local crystal anisotropy across laminates together with the optimized layered arrangement are essential for their mechanical behavior. By the example of a laminate consisting of brittle CrN and ductile Cr layers, enhanced material properties are achieved by taking advantage of the self assembly mechanisms of the heterogeneous material during film growth. The usage of local microstructure analysis by a synchrotron based technique as well as miniature mechanical tests allow to understand the relationship between the apparent local microstructure and the accompanied mechanical properties. A crystallographic orientation relationship between Cr and CrN is elucidated, which leads to decisive mechanical enhancement due to microstructural benefits in terms of texture. This results in enhanced strength and fracture toughness of the laminate compared to its single constituents. The systematic approach gives an insight into the complex coherences of laminate materials, where the used techniques and design principles are universally applicable.

Cu diffusion in single-crystal and polycrystalline TiN barrier layers: A high-resolution experimental study supported by first-principles calculations

Dense single-crystal and polycrystalline TiN/Cu stacks were prepared by unbalanced DC magnetron sputter deposition at a substrate temperature of 700 °C and a pulsed bias potential of −100 V. The microstructural variation was achieved by using two different substrate materials, MgO(001) and thermally oxidized Si(001), respectively. Subsequently, the stacks were subjected to isothermal annealing treatments at 900 °C for 1 h in high vacuum to induce the diffusion of Cu into the TiN. The performance of the TiN diffusion barrier layers was evaluated by cross-sectional transmission electron microscopy in combination with energy-dispersive X-ray spectrometry mapping and atom probe tomography. No Cu penetration was evident in the single-crystal stack up to annealing temperatures of 900 °C, due to the low density of line and planar defects in single-crystal TiN. However, at higher annealing temperatures when diffusion becomes more prominent, density-functional theory calculations predict a stoichiometry-dependent ...

Microstructure-controlled depth gradients of mechanical properties in thin nanocrystalline films: Towards structure-property gradient functionalization

Although the influence of the grain size on the mechanical properties of polycrystalline materials is well understood, the occurrence of depth-gradients of grain size, microstructure, and residual stresses in nanocrystalline thin films and their effect on the functional properties is a phenomenon which has not yet been studied in detail. Hence in this work, single-layered polycrystalline and mosaic epitaxial as well as multilayered CrN thin films were characterized by a combination of averaging as well as depth-resolved experimental techniques, such as cross-sectional X-ray nanodiffraction and small-angle cross-sectional nanoindentation. The results reveal the fundamental relationship between gradients of grain size, microstructure, and stresses, controlled by the film growth conditions, and gradients of hardness and elastic modulus. The effect of the compressive stress and structural defects associated with high particle energy on the mechanical properties of nanocrystalline thin films was found to be do...

The chemical composition of tetrahedrite-tennantite ores from the prehistoric and historic Schwaz and Brixlegg mining areas (North Tyrol, Austria)

The copper ore occurrences from Schwaz and Brixlegg were mined both in prehistoric and historic times. The ores occur as discordant veins, strata-bound bodies and breccias in the Devonian Schwaz Dolomite of the Northern Greywacke Zone. The ore mineral assemblage is characterized by more or less monomineralic Fe-Zn-Hg-bearing tetrahedrite-tennantite. Especially in the Groskogel mining area in Brixlegg, barite is associated with the tetrahedrite-tennantite ores. To characterize the compositional variations of tetrahedrite-tennantite a comprehensive electron microprobe investigation involving the analysis of 21 elements was conducted. The mining areas of Schwaz and Brixlegg can be distinguished by their chemical and mineralogical compositions. Whereas fahlore from Schwaz is a strongly zoned Fe-Zn tetrahedrite-tennantite solid solution (10.4 % to 59.8 % tennantite component, 21.8–71.8 % Zn end-member) with high Hg (≤5.56 wt%) and low Ag (≤0.80 wt%) concentrations, fahlore from Brixlegg, also strongly zoned, is generally richer in Zn (47.8–97.1 % Zn end-member) and poorer in Hg ( ≤2.11 wt%) with comparable low Ag concentrations. The mineralogical differences are basically due to the tetrahedrite-tennantite breakdown textures in ores from Brixlegg leading to the assemblage enargite/luzonite-famatinite + sphalerite + pyrite + stibnite + chalcostibite, or fahlore (second generation) + enargite/luzonite-famatinite +sphalerite +pyrite +stibnite +chalcostibite and fahlore (second generation) +sphalerite +pyrite +stibnite + chalcostibite. The following model reactions explaining these reaction assemblages can be proposed: Cu 10 Fe 2 Sb 4 S 13 + Cu 10 Fe 2 As 4 S 13 + 13 / 4 S 2 → 1 / 2 Cu 10 Fe 2 Sb 4 S 13 + 1 / 4 Cu 10 Fe 2 As 4 S 13 + 3 Cu 3 AsS 4 + Cu 4 SbS 4 + 1 / 2 CuSbS 2 + 1 / 4 Sb 2 S 3 + 5 / 2 FeS 2 Cu 10 Fe 2 Sb 4 S 13 + Cu 10 Fe 2 As 4 S 13 + 5 S 2 → 3 Cu 3 AsS 4 + 2 Cu 3 SbS 4 + 2 CuSbS 2 + 4 FeS 2 Cu 10 Zn 2 Sb 4 S 13 + Cu 10 Zn 2 As 4 S 13 + 2 S 2 → 1 / 2 Cu 10 Zn 2 Sb 4 S 13 + 1 / 4 Cu 10 Zn 2 As 4 S 13 + 3 Cu 3 AsS 4 + Cu 3 SbS 4 + 1 / 2 CuSbS 2 + 1 / 4 Sb 2 S 3 + 5 / 2 ZnS Cu 10 Zn 2 Sb 4 S 13 + Cu 10 Zn 2 As 4 S 13 + 3 S 2 → 4 Cu 3 AsS 4 + 2 Cu 3 SbS 4 + 2 CuSbS 2 + 4 ZnS Thermodynamic modelling of these breakdown reaction textures shows that either local-scale variations in sulphur fugacity , f S 2 , and/or decreasing temperature , T , result in the breakdown of the fahlores. The presented chemical and mineralogical data were subsequently compared to ore-fragments, copper slags and raw copper from mining archaeological excavations at the Kiechlberg Early Bronze Age copper smelting site near Innsbruck (Tirol, Austria). Excavated ore fragments contain tetrahedrite-tennantite with similar Fe-Zn-Hg concentrations and breakdown textures as described from the Brixlegg mining district. Several raw copper fragments also yielded similar high Sb-, As- and Ag-concentrations. These observations indicate 1) the use of fahlore-copper smelting and 2) local-scale import of copper-ore from Brixlegg.

Enhanced Ti0.84Ta0.16N diffusion barriers, grown by a hybrid sputtering technique with no substrate heating, between Si (001) wafers and Cu overlayers

We compare the performance of conventional DC magnetron sputter-deposited (DCMS) TiN diffusion barriers between Cu overlayers and Si(001) substrates with Ti0.84Ta0.16N barriers grown by hybrid DCMS/high-power impulse magnetron sputtering (HiPIMS) with substrate bias synchronized to the metal-rich portion of each pulse. DCMS power is applied to a Ti target, and HiPIMS applied to Ta. No external substrate heating is used in either the DCMS or hybrid DCMS/HiPIMS process in order to meet future industrial thermal-budget requirements. Barrier efficiency in inhibiting Cu diffusion into Si(001) while annealing for 1 hour at temperatures between 700 and 900 °C is investigated using scanning electron microscopy, X-ray diffraction, four-point-probe sheet resistance measurements, transmission electron microscopy, and energy-dispersive X-ray spectroscopy profiling. Ti0.84Ta0.16N barriers are shown to prevent large-scale Cu diffusion at temperatures up to 900 °C, while conventional TiN barriers fail at ≤700 °C. The improved performance of the Ti0.84Ta0.16N barrier is due to film densification resulting from HiPIMS pulsed irradiation of the growing film with synchronized Ta ions. The heavy ion bombardment dynamically enhances near-surface atomic mixing during barrier-layer deposition.

X-ray nanodiffraction analysis of stress oscillations in a W thin film on through-silicon via

X-ray nanodiffraction is used to evaluate axial and tangential residual stress distributions in a W thin film deposited on the scalloped inner wall of a through-silicon via. The results reveal oscillatory stress distributions which correlate well with the scallop wavelength and morphology.

Combinatorial refinement of thin-film microstructure, properties and process conditions: iterative nanoscale search for self-assembled TiAlN nanolamellae

A novel iterative combinatorial nanoscale search based on the application of cross-sectional synchrotron X-ray nanodiffraction and cross-sectional nanoindentation is used to refine the relationship between deposition conditions, microstructure and properties of nanostructured TiAlN thin films. Using three iterative steps, a nanolamellar TiAlN thin film with a maximal hardness of ∼36 GPa is developed.