TiN Crystallites Research Articles

X-ray scattering study of GaN nanowires grown on Ti/Al2O3 by molecular beam epitaxy.

GaN nanowires (NWs) grown by molecular beam epitaxy on Ti films sputtered on Al2O3 are studied by X-ray diffraction (XRD) and grazing-incidence small-angle X-ray scattering (GISAXS). XRD, performed both in symmetric Bragg reflection mode and at grazing incidence, reveals Ti, TiN, Ti3O, Ti3Al and Ga2O3 crystallites with in-plane and out-of-plane lattice parameters intermediate between those of Al2O3 and GaN. These topotaxial crystallites in the Ti film, formed as a result of interfacial reactions and N exposure, possess little misorientation with respect to Al2O3. As a result, GaN NWs grow on the top TiN layer, possessing a high degree of epitaxial orientation with respect to the substrate. The measured GISAXS intensity distributions are modelled by the Monte Carlo method, taking into account the orientational distributions of NWs, the variety of their cross-sectional shapes and sizes, and the roughness of their side facets. The cross-sectional size distributions of the NWs and the relative fractions of the {1100} and {1120} side facets are determined.

Microstructure, mechanical properties, and corrosion resistance of TiSiN coating prepared by FCVA technique with different N2 flow rates

TiSiN coatings have attracted extensive attention due to excellent performance in cutting tools, Marine engineering equipment and ship critical components. However, due to the many microparticles and micropores on the coating surface prepared by traditional PVD techniques, the performance of the coatings, especially corrosion resistance, is seriously affected. Therefore, the preparation of high quality TiSiN coatings is very important for the industrial applications. In this study, high-quality TiSiN coatings were prepared by FCVA technique. The effect of N2 flow rate on microstructure, mechanical properties and corrosion resistance of TiSiN coating was investigated. The results showed that all TiSiN coatings presented smooth and compact microstructure without cracks. Meanwhile, TiSiN coatings had a nanocomposite structure of amorphous Si3N4 encapsulated TiN crystallites and possessed a preferred orientation of TiN (200) plane. With the increase of N2 flow rate, the grain size and hardness increased first and then decreased. When N2 flow rate is 20 sccm, the hardness of TiSiN coating reached the maximum owing to the fine grain strengthening effect. Moreover, TiSiN coating deposited N2 flow rate of 40 sccm had the best corrosion resistance, with the highest charge transfer resistance and pore resistance, which was primarily related to the best surface quality.

Effect of DC power on the thickness, hardness and adhesion strength of Ti-51 at% Ni coated Ti/TiN

The coating of Ti/TiN was successfully deposited on Ti-51 at% Ni substrates by using direct current (DC) magnetron sputtering technique and the effect of different sputtering power on the thickness, surface hardness and adhesion strength of the coatings were studied. The microstructural characterization was carried out using scanning electron microscope (SEM), energy-dispersive X-ray (EDX) and X-ray diffractometer (XRD). The coating thicknesses were detected and measured using SEM. The surface hardness test was performed using microhardness tester, and the adhesion strength was carried out by scratch testing. The results showed that the TiN crystallites growth orientation, thickness, surface hardness and adhesion strength are influenced by sputtering power. As power increased from 300 W to 370 W, peaks at (111), (200) and (311) increased while peaks at (200) and (222) decreased, substrate hardness increased by 53.42%, thickness increased from 2.278 μm to 2.389 μm, and adhesion strength also increased from 3000 mN to 3998 mN. Meanwhile, a decrease in thickness, hardness, adhesion strength, all the peaks and total disappearance of peak (222) were all noticed at 440 W.

Effect of carbon addition on tribological performance of TiSiN coatings produced by cathodic arc physical vapour deposition

Effect of carbon addition on tribological behaviour of multilayered TiSiN coating was investigated and the performance of TiSiCN and TiSiN coatings on cold forming steel dies were compared. The coatings were deposited by an industrial cathodic arc physical vapour deposition process. Surface analysis by X-ray diffraction and micro-Raman spectroscopy revealed that structure of TiSiN was mainly composed of TiN crystallites together with a silicon-rich amorphous phase. In the case of TiSiCN coating, presence of Ti(C, N) crystallites, graphite and amorphous carbon were identified. Both coatings contained high compressive residual stresses, as measured by sin2ψ method. Nanoindentation testing showed hardness values of 25 GPa and 29 GPa for TiSiN and TiSiCN, respectively. Tribological tests, conducted on a ball-on-disc wear tester using zirconia ball, indicated lower coefficient of friction of the coatings as compared to the steel substrate; the lowest value of 0.2 was experienced by TiSiCN coated surface. Study of wear mechanisms proved that application of coatings changed the prevailing wear mode from adhesive to abrasive, decreasing the wear rate to one third. Addition of carbon to TiSiN changed tribological behaviour of the coating, similar to a self-lubricant film. Field tests of TiSiCN coating on forming dies, for deep drawing operation of steel tubes, revealed 10 times increase of die lifetime.

Microstructure, adhesion strength and thermal conductivity of AlN/(Ti, W)/Cu substrate system

AlN/(Ti, W)/Cu substrates were successfully fabricated by the combination of magnetron sputtering and electroless copper plating, exhibited layered distribution without obvious defects or delamination. The adhesion film in AlN/Ti/Cu was composed of TiN, Al, and Ti crystallites due to the reaction between the sputtered Ti layer and the AlN substrate, while in AlN/W/Cu was α-W and β-W crystallites with a mixed distribution but a thin W-rich amorphous layer at the interface towards Cu contact. In AlN/TiW/Cu was W-rich TixW1−x and α-Ti with the interlayer distribution. The scratch failure of the AlN/(Ti, W)/Cu substrates included the peeling of the Cu plating layer and adhesion film. The nanoscale hard phase layered combination of the adhesion film in AlN/TiW/Cu exhibited better peeling resistance, resulting in the most prominent adhesion strength among the substrate system. The existence of an amorphous layer in AlN/W/Cu led to the lower thermal conductivity. AlN/TiW/Cu substrate showed good comprehensive properties including adhesion strength and thermal conductivity.

Multi-scale interface design of strong and damage resistant hierarchical nanostructured materials

Synthesis of damage resistant nanostructured materials with high strength and fracture toughness is a challenging task. In this work, multi-scale interfaces were implemented into a hierarchical TiN/SiOx microstructure to mimic stepwise crack growth behaviour of the hard and damage resistant bivalve mollusc Saxidomus purpuratus shell. In situ micromechanical testing in scanning and transmission electron microscopes revealed multi-scale crack deflection events at grain boundaries of individual alternately-tilted TiN crystallites, at kinks of their repeatedly tilted columnar grains as well as crack interaction with perpendicular interfaces of elastic amorphous SiOx layers. These events induced an increase in the crack surface area, reduction of the crack driving force and dissipation of local stress and energy at the crack tip with subsequent crack slow-down or arrest, resulting in fracture toughness exceeding by ~200% the toughness of monolithic TiN nanoceramics. By this perspective biomimetic microstructural design, catastrophic failure of brittle ceramics may be turned into a predictable and controllable process increasing reliability of strong materials in various challenging safety-critical engineering applications. It also shows potential paths for the development of strong and simultaneously tough materials with high mechanical and thermal stability.

Zero temperature coefficient of resistance in back-end-of-the-line compatible titanium aluminum nitride films by atomic layer deposition

Thin film resistors with near-zero temperature coefficient of resistance (TCR) are key passive elements in analog integrated circuits (ICs). State-of-the-art near-zero TCR technology is based on sputtered compounds of Si, Cr, B, and C, which require annealing at temperatures higher than 500 °C, making it incompatible with back-end-of-the-line (BEOL) processes. We report here that near-zero TCR resistors can be obtained by atomic layer deposition (ALD) of TiN-AlN nano-laminates at BEOL-compatible deposition temperature. The resistivity and the TCR can be tuned by varying the ratio between AlN (insulating) and TiN (metallic) in the TiXAl1−XN thin film. The TCR changes from positive to negative as the AlN content is increased, allowing for optimization to zero TCR. The ALD method provides ultimate control of the thickness, composition ratio, coverage, and uniformity. Microstructure analysis shows that the film consists of metallic TiN crystallites embedded in the semiconducting TiyAl1−yN amorphous matrix, suggesting that the electrical behavior is similar to that of SiCr-based compounds. These results pave the way toward BEOL-compatible near-zero TCR thin film resistors, which can significantly reduce capacitance and minimize design complexity of passive analog IC components.

Correlating elemental distribution with mechanical properties of TiN/SiNx nanocomposite coatings

Detailed structural and chemical analyses reveal that Ti-Si-N coatings prepared with high nitrogen partial pressure and temperature are composed of nm-sized (nearly equiaxed) TiN crystallites encapsulated by ~1.0 nm thin Si-rich tissue phase. This nanocomposite structure allows for superior hardness (37.6 ± 1.5 GPa) and fracture toughness (4.5 ± 0.6 MPa√m). Contrary, deposition at lower nitrogen partial pressure and temperature does not allow for such a clear Si segregation during film growth, leading to nm-sized solid solution Ti1-xSixN crystallites. Although having the same Si content of 8.5 at.%, their hardness (32.1 ± 0.9 GPa) as well as fracture toughness (3.0 ± 0.2 MPa√m) is significantly lower.

TiSiN(Ag) films deposited by HiPIMS working in DOMS mode: Effect of Ag content on structure, mechanical properties and thermal stability

TiSiN(Ag) coatings with Ag contents ranging from 0 to 29 at.% were designed as promising materials to allow long term solid lubrication during dry machining operations. Here, we report the influence of Ag additions on the properties of TiSiN(Ag) films deposited by high power impulse magnetron sputtering- HiPIMS, working in deep oscillation magnetron sputtering mode – DOMS. Introduction of silver pellets on the target progressively increases the Ag concentration on the films, influencing the deposition rate, structure and morphology of the films. All the coatings display crystalline peaks assigned to a TiN fcc NaCl type structure. Ag additions to the reference TiSiN film, significantly broadens the TiN diffraction peaks and abruptly decreases the grain size of the TiN crystallites from 24 nm to 11–7 nm. Grain size was then found to be independent of the silver content on the films. Hardness and Young's modulus of the coatings decreased with increasing Ag additions mainly due to the increase of this soft phase on the microstructure. An increase in the peak power was observed when 6 at.% Ag was added which revealed a transition from a columnar to a very compact morphology, a decrease of the deposition rate and an increase of the lattice parameter for this coating. A reverse in the morphology is then perceived for the higher Ag concentration (29 at.%). Annealing treatment didn't present any significant changes in the structure/phase composition or mechanical properties of the coatings. Elemental maps and profiles allowed perceiving the formation of a very thin dual layer where a top Ag rich layer is formed due to the diffusion of silver from the Ag deficient TiSiN layer below.

Microstructural evolution, mechanical properties and strengthening mechanism of TiN/Ni nanocomposite film

A series of TiN/Ni nanocomposite films with different Ni content were synthesized by reactive magnetron sputtering. The microstructural evolution, mechanical properties and strengthening mechanism of TiN/Ni nanocomposite film were studied. When Ni:Ti ratio is less than 1:24, the small amount of Ni can be dissolved in the TiN matrix, leading to the slight decrease of the hardness and elastic modulus. When Ni:Ti ratio rises to 4:21, Ni inclines to separate from TiN due to the thermodynamic incompatibility as an interfacial phase and grow coherently with adjacent TiN crystallites. As a result, the TiN/Ni film was remarkably strengthened with the maximal hardness and elastic modulus of 33.3 GPa and 373 GPa. As Ni:Ti ratio further increases to 5:20, Ni interface transforms into amorphous state, leading to the destruction of the epitaxial growth structure and the rapid decrease of hardness and elastic modulus. The strengthening effect of TiN/Ni nanocomposite film can be attributed to the coherent interface between Ni interfacial layers and TiN crystallites.

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.

Photoluminescence and compositional-structural properties of ion-beam sputter deposited Er-doped TiO2−xNx films: Their potential as a temperature sensor

Er-doped TiO2−xNx films were grown by Ar+ ion-beam sputtering a Ti + Er target under different N2 + O2 high-purity atmospheres. The compositional-structural properties of the samples were investigated after thermal annealing the films up to 1000 °C under a flow of oxygen. Sample characterization included x-ray photoelectron spectroscopy, grazing incidence x-ray diffraction, Raman scattering, and photoluminescence experiments. According to the experimental data, both composition and atomic structure of the samples were very sensitive to the growth conditions and annealing temperature. In the as-deposited form, the N-rich TiO2−xNx films presented TiN crystallites and no photoluminescence. As the thermal treatments proceed, the films were transformed into TiO2 and Er3+-related light emission were observed in the visible and near-infrared ranges at room-temperature. Whereas the development of TiO2 occurred due to the insertion-diffusion of oxygen in the films, light emission originated because of optical bandgap widening and/or structural-chemical variations in the vicinity of the Er3+ ions. Finally, the photoluminescence results in the visible range suggested the potential of the present samples in producing an optically based temperature sensor in the ∼150–500 K range.

Tailoring the nanostructure of Ti–Si–N thin films by HiPIMS in deep oscillation magnetron sputtering (DOMS) mode

Nanocomposite TiSiN films consist of nano-sized TiN crystallites surrounded by an amorphous Si–N matrix. Many works have shown that the hardness of nanostructured TiSiN films increases with increasing silicon content up to an optimal concentration. However, energetic ion bombardment of the growing film also influences the hardness and structure of TiSiN films. The main objective of the present work was to tailor the nanostructure of TiSiN films by using the highly ionized fluxes of sputtered material generated in a HiPIMS discharge. For this purpose TiSiN films were deposited by DOMS (deep oscillation magnetron sputtering) mode. The energetic ion bombardment of the growing films was controlled by changing the peak power.The crystal structure of TiSiN films was analyzed by X-ray diffraction (XRD) with a parallel beam in both θ–2θ and GIXRD geometries. EDS and XPS were used to elucidate the chemical composition of the films and the nature of the chemical bonding, respectively. The microstructure of the films was characterized by SEM while their mechanical properties were measured by nanoindentation.All the films deposited by DOMS have a nanocomposite microstructure consisting of two phases: f.c.c TiN and a-SiN. Although similar amounts of SiN were detected in the films, both the phase distribution and the properties of the f.c.c phase depend on the peak power. Two deposition regimes were identified. At low peak power (up to 44kW) the growing film is bombarded with a high flux of low energy ionized sputtered species promoting the surface mobility of the ad-atoms and avoiding the atomic peening effect. At high peak power the energetic species impinging on the substrate are able to penetrate in the sub-surface of the growing film, resulting in an intense atomic peening effect which ultimately leads to secondary nucleation due to the high number of defects.

Nanocrystalline nitride coatings deposited by vacuum arc plasma-assisted method

In the given work, experiments on research of formation of titanium nitride doped with copper (≤12 at %) produced by plasma-assisted vacuum arc deposition by evaporation of sintered Ti-Cu cathodes were carried out. It was revealed that Ti-Cu-N coatings have high hardness (≈40 GPa), high elastic recovery (≥50%), low friction coefficient (≈0.2) and high adhesion to a substrate compared with typical TiN coatings. By methods of transmission electron microscopy of thin foils and x-ray diffraction, it was showed that the coating crystallites consist of δ-TiN with the average crystallite size of 10-30 nm and the sheath of doping elements (copper) with thickness of 2-3 monolayers is formed around of TiN crystallites.

Characterization and Mechanical Properties of Ti–Al–Cr–N Nanocomposite Coatings Deposited by Closed Field Unbalanced Middle Frequency Magnetron Sputtering

Ti–Al–Cr–N coatings, characterized by a nanocomposite comprising nano-sized TiN crystallites embedded in amorphous AlN or CrN matrix, could be successfully synthesized on Si(111) and WC–Co cemented carbide substrates by a closed field unbalanced middle frequency magnetron sputtering method. The Cr content in the Ti–Al–Cr–N coatings linearly increased from 11.2 to 32.8 at. % raising the Cr targets currents from 5 to 15 A, whereas the Ti content decreased from 63 to 47 at. %. The high resolution transmission electron microscope (HRTEM) image and diffraction patterns clearly show that the Ti–Al–Cr–N coatings were composites of crystallites and amorphous phase, which were distinguished from each other by lattice fringe contrast. The hardness and Young's modulus value of the Ti–Al–Cr–N coatings increased with incorporation of Cr, and had the maximum value of 38.9 and 475 GPa at the Cr content of 17 at. %, respectively. The average friction coefficient of the Ti–Al–Cr–N coatings largely decreased with an increase of the Cr content when compared to the TiN coatings.

Characterisation and corrosion resistance of TiN–Ni nanocomposite coatings using RBS and NRA

Nanocomposite TiN–Ni coatings were produced by a duplex treatment on Ti–6Al–4V substrates. The procedure consisted of plasma nitriding of the substrate followed by deposition of a TiN–Ni layer by sputtering a composite Ti–Ni target with 1.2 keV Ar + ions. The growing film was bombarded during deposition by a mixture of 50 eV Ar +–N 2+–N + ions. The temperature as well as the Ni- and the N-content of the coatings varied in order to obtain the optimum structural and mechanical properties. The surface morphology of the coatings was examined by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The results showed that Ni appears as an amorphous phase around the TiN crystallites. The thickness and the composition of the coatings were investigated by Rutherford Backscattering Spectrometry (RBS) using deuterons as projectiles. The nitrogen depth distribution in the coatings was determined by Nuclear Reaction Analysis (NRA) using 14N(d, α) and 14N(d, p) nuclear reactions. The corrosion resistance of the nitrided and non-nitrided coatings in aggressive environment (NaCl 3% solution at RT) was investigated using electrochemical techniques (potentiodynamic polarisation and cyclic voltammetry). It was found that nanocomposite coatings are stable and do not influence the corrosion resistance of the Ti-alloy substrate. The nitrided coatings exhibited higher wear and corrosion resistance related with their Ni-content.

Microstructure and mechanical properties of Ti–Si–C–N coatings deposited by hybrid arc enhanced magnetron sputtering

Quaternary Ti–Si–C–N coatings have been deposited on high speed steel substrates using a new hybrid arc enhanced magnetron sputtering (AEMS) technique conducted at low temperature. The microstructure and mechanical properties of the deposited Ti–Si–C–N coatings are investigated and the results show that the Ti–Si–C–N coatings have a nanocomposite microstructure consisting of nanosized TiN and TiC crystallites embedded in an amorphous phase of Si3N4/C. The hardness of the Ti–Si–C–N coatings increases linearly from 20 to 35 GPa with carbon incorporation up to 35 at.-% and the friction coefficient is below 0·25 which is smaller than that of ternary Ti–Si–N nanocomposite coatings.

Synthesis Ti–Si–N nanocomposite coating prepared by a hybrid system of double bending filtered vacuum arc source and magnetron sputtering

In this work, various nanocomposite Ti–Si–N films have been deposited by hybrid coating system of double bending filtered vacuum arc source (DBFVAS) and magnetron sputtering techniques. Vacuum arc source has been used for the deposition of TiN and Si was incorporated by magnetron sputtering. The magnetic system of double bending filter consists of five solenoid coils and additional coil on the opposite side of vacuum chamber is supporting stabilization of the plasma flow onto substrate surface. Ti–Si–N film is deposited on the Si wafers and high speed steel (HSS) substrates with different Si content, which is controlled by magnetron current. As magnetron current increases from 0 to 1.5 A, Si content increases up to 18.2%. The deposition rate of Ti–Si–N coating layer is up to 17 nm/min. From the results Ti–Si–N coatings have been characterized as nanocomposites, consists of TiN crystallites and amorphous Si 3N 4.

Effect of Si Addition on the Corrosion Behavior of Ti–Si–N Coatings Prepared by a Hybrid Coating System

Ti-Si-N coatings were deposited on stainless steel substrates using a hybrid coating system consisting of arc ion plating for Ti and a dc magnetron sputtering technique for Si in a gaseous N 2 /Ar mixture. On increasing the Si content in the Ti-Si-N coating, the microstructure changed from columnar to a nanocomposite. The anodic polarization measurement performed in 3 wt % NaCl solutions at room temperature revealed that Ti-Si-N coatings with higher Si contents had better corrosion resistance due to the formation of a unique nanocomposite microstructure where the highly corrosion-resistive amorphous SiN x phases surrounded the TiN crystallites.

Effect of Silane Flow Rate on Structure and Corrosion Resistance of Ti–Si—N Thin Films Deposited by a Hybrid Cathodic Arc and Chemical Vapour Process

Ti–Si–N thin films with different silicon contents are deposited by a cathodic arc technique in an Ar+N2 +SiH4 mixture atmosphere. With the increase of silane Bow rate, the content of silicon in the Ti–Si–N films varies from 2.0 at. % to 12.2 at. %. Meanwhile, the cross-sectional morphology of these films changes from an apparent columnar microstructure to a dense fine-grained structure. The x-ray diffractometer (XRD) and x-ray photoelectron spectroscopy (XPS) results show that the Ti–Si–N film consists of TiN crystallites and SiNx amorphous phase. The corrosion resistance is improved with the increase of silane Bow rate. Growth defects in the films produced play a key role in the corrosion process, especially for the local corrosion. The porosity of the films decreases from 0.13% to 0.00032% by introducing silane at the Bow rate of 14sccm.