CrN Thin Films Research Articles

The effect of growth parameters on CrN thin films grown by molecular beam epitaxy

In this paper, we report on the controlling of the effect of growth parameters such as substrate temperature and the ratio of Cr and N atoms on phase formation, surface morphology and crystallization of CrN(001) thin films grown by plasma-assisted molecular beam epitaxy on the MgO(001) substrate. The reflection high energy electron diffraction, atomic force microscopy, X-ray diffraction and scanning tunneling microscopy are used to characterize the thin films grown under various conditions. High-quality CrN(001) thin films are achieved at a substrate temperature 430 °C with a low Cr deposition rate.

Study of the Adhesion and the Thermal Stability of CrN and CrAlN Thin Films

The chromium nitride thin layers have became more and more popular in the last decade because of their good physical, chemical and mechanical properties. The present study deals the morphological characterization of hard Cr-N and CrAlN thin layers deposited on silicon (100) substrates by physical vapour deposition (PVD). The effect of the annealing temperature on the adherence and the thermal stability of CrN layers are considered. SEM observations and EDS microanalyses were performed. Cr-N films, 1μm thick, were annealed for 1 hour at 600 to 1000°C under flux of nitrogen. These layers presented a good thermal stability at low temperatures. Moreover SEM observations showed that the CrN films had a low adhesion at high temperatures. In addition, after annealing at 700°C for 4 hours, CrAlN coating of 1μm thickness presents a better thermal stability than CrN coating but with lower adherence. The results given by SEM-EDS and XRD are compared.

S043022 CrN薄膜を被覆したチタン合金のフレッティング疲労特性([S04302]環境調和型の表面改質および薄膜コーティング(2))

S043022 CrN薄膜を被覆したチタン合金のフレッティング疲労特性([S04302]環境調和型の表面改質および薄膜コーティング(2))

Fourier-Transform Infrared Absorption Spectroscopy of Chromium Nitride Thin Film

Chromium nitride thin films were deposited by RF reactive unbalanced magnetron sputtering on (100) Si single-crystal or glassy carbon substrates. The characteristics of the thin films were measured by Rutherford backscattering spectroscopy, X-ray diffractometry, and scanning electron microscopy. From the results of the above measurements, it was found that our samples were stoichiometric chromium nitride thin films. The chemical bonding state was estimated using the results of the Fourier-transform infrared spectroscopy. A peak attributed to the Cr–N bond was observed at around 380 cm-1, and it could be obtained with any beam splitter and atmosphere. Furthermore, the influence of residual stress was also investigated. Residual stresses of CrN thin films, which were calculated from their strains, were quite low.

S043014 CrN薄膜の密着性に及ぼす基板前処理及び基板材料の影響([S04301]環境調和型の表面改質および薄膜コーティング(1))

In this study, influence of substrate material and ion bombardment pretreatment on adhesion of CrN film is examined on the basis of surface free energy measurement. Four materials: pure aluminum alloy, super duralumin, high-speed tool steel, and pure titanium alloy are used as substrates. Before CrN deposition, ion bombardment pretreatment is performed in order to remove surface contamination. Ion bombardment process is carried out in nitrogen or argon atmosphere under various gas flow rate. Surface free energy is measured by sessile drop method using distilled water and methylene iodide. Critical load of CrN film is examined using the scratch tester. The influence of venting after ion bombardment process on the critical load is also examined. As a result, surface free energy, especially polar component, decreased after ion bombardment process. Critical load decreased with increasing the polar component of surface free energy. The critical load increases with decreasing the polar component of surface free energy, in particular, SKH-2 substrate.

S043021 ナノインデンテーション法を用いたCrN薄膜の破壊靭性の評価([S04302]環境調和型の表面改質および薄膜コーティング(2))

S043021 ナノインデンテーション法を用いたCrN薄膜の破壊靭性の評価([S04302]環境調和型の表面改質および薄膜コーティング(2))

Room temperature ferromagnetism and hopping transport in amorphous CrN thin films

Magnetic and electronic properties of stoichiometric amorphous CrN thin films grown on MgO (001) substrates by radio-frequency nitrogen-plasma-assisted molecular beam epitaxy have been investigated. The magnetic property of the amorphous CrN thin films shows a ferromagnetic behavior even at room temperature, and can be interpreted by the percolation theory of magnetic polaron where we consider Cr3+ defects as magnetic impurities which lead to the formation of bound magnetic polarons. The obtained results of electrical conductivity are explained by the variable-range-hopping theory of the Mott and Davis model.

Effect of sputtering pressure and temperature on DC magnetron sputtered CrN films

Chromium nitride thin films were deposited on Si(100) substrate by using DC magnetron sputtering and the influence of process parameters such as substrate temperature, pressure and power on their microstructural characteristics were investigated in the present work. The CrN films were characterised with X-ray diffraction and it was observed that the films exhibit (111) preferred orientation but it transforms in to (200) orientation with increasing working pressure. The preferred orientations of CrN thin films are strongly influenced by sputtering conditions, thickness and the induced microstrain in the thin films. Field emission scanning electron microscopy and atomic force microscopy were used to characterise the morphology and surface topography of the CrN thin films respectively. The as deposited CrN films exhibited columnar morphology and its surface roughness values were influenced by the working pressure and temperature. Similarly, the microstrain in the films exhibited a strong dependence on deposition conditions.

Estimation of the stress relief induced in CrN thin films by buckling

Previous studies have revealed that thin PVD coatings submitted to repeated impacts may undergo blister formation which appears to be the first damage step leading to spalling. From mechanical analysis, the blister formation is likely to be related to a critical compressive stress value depending on the film thickness and on the size of the interfacial defects. In this model, a blister formation should then lead to a local stress relief. To show this induced stress evolution, micro-Raman spectroscopy was used in this study on both untreated and buckled CrN thin films. Thanks to the localized analysis, microstructure and stress modifications in the impacted area were detected. They can be related to the mechanical model generally used to explain the observed failure mechanisms. Stress reliefs of about 1.6 and 2.2 GPa have been detected on buckled CrN films of various thicknesses whereas structural damages are observed in worn impact scares.

Ion-beam irradiation effects on reactively sputtered CrN thin films

The present study deals with CrN/Si bilayers irradiated at room temperature (RT) with 120 keV Ar ions. The CrN layers were deposited by d.c. reactive sputtering on Si(1 0 0) wafers, at different nitrogen partial pressures (2 × 10 −4, 3.5 × 10 −4 and 5 × 10 −4 mbar), to a total thickness of 240–280 nm. The substrates were held at room temperature (RT) or 150 °C during deposition. After deposition the CrN/Si bilayers were irradiated up to fluences of 1 × 10 15 and 1 × 10 16 ions/cm 2. Structural characterization was performed with Rutherford backscattering spectroscopy (RBS), cross-sectional transmission electron microscopy (XTEM) and grazing angle X-ray diffraction (XRD). For the highest nitrogen pressure (5 × 10 −4 mbar) a pure stoichiometric CrN phase was achieved. The results showed that Ar ion irradiation resulted in the variation of the lattice constants, micro-strain and mean grain size of the CrN layers. The observed microstructural changes are due to the formation of the high density damage region in the CrN thin film structure.

Adhesion of Human Osteoblasts Cell on CrN Thin Film Deposited by Cathodic Arc Plasma Deposition

Interaction between human osteoblast (hFOB 1.19) and CrN films was conducted in vitro. CrN films were produced by cathodic arc plasma deposition. The surface was characterized by atomic force microscopy (AFM). CrN films, glass substrates and TiN films were cultured with human osteoblasts for 48 and 72 hours. Actin stress fiber patterns and cell adhesion of osteoblasts were found less organized and weak on CrN films compared to those on the glass substrates and the TiN films. Human osteoblasts also showed less proliferation and less distributed microtubule on CrN films compared to those on glass substrates and TiN films. Focal contact adhesion was not observed in the cells cultured on CrN films, whereas focal contact adhesion was observed well in the cells cultured on glass substrates and TiN films. As a result, the CrN film is a potential candidate as a surface coating to be used for implantable devices which requires minimal cellular adhesion.

Cell adhesion property of cathodic arc plasma deposited CrN thin film

The interaction between human osteoblast cells and CrN thin film was studied in vitro. CrN thin films were produced by cathodic arc plasma deposition. The surface was characterized by atomic force microscopy. Cell adhesion on the coatings was assessed by MTT assay and visualization. Cell cytoskeleton organization was studied by analyzing microtubule and actin cytoskeleton organization. Focal contact adhesion was monitored by analyzing vinculin density. The study found that the CrN thin film is a potential candidate as a protective coating on implantable devices that require minimal cellular adhesion.

Elastic constants of fibre-textured thin films determined by X-ray diffraction

A new methodology is presented that allows the rapid determination of elastic constants of cubic fibre-textured thin films by X-ray diffraction. The theoretical concept is developed and tested on calculated examples of Cu and CrN films. The mechanical elastic constants are extrapolated from X-ray elastic constants by taking into consideration crystal and macroscopic elastic anisotropy. The derived algorithm enables the determination of a reflection and the corresponding value of the X-ray anisotropic factor Γ for which the X-ray elastic constants are equal to their mechanical counterparts in the case of fibre-textured cubic polycrystalline aggregates. The approach is independent of the crystal elastic anisotropy and depends on the fibre-texture type, the texture sharpness, the number of randomly oriented crystallites and the supposed grain-interaction model. In the experimental part, out-of-plane Young's moduli of 111 and 311 fibre-textured Cu and CrN thin films deposited on monocrystalline Si(100) substrates are determined. The moduli are extrapolated from thin-film experimental X-ray elastic constants that are determined by a combination of X-ray diffraction substrate curvature and sin(2)ψ methods. For the calculation, the film macroscopic elastic anisotropy (texture) is considered. The advantage of the new technique lies in the fact that experimental moduli are determined nondestructively, using a static diffraction experiment, and represent volume-averaged quantities.

ホロカソード型イオンプレーティングで作製したCr-N系薄膜(HDCr)の評価

ホロカソード型イオンプレーティングで作製したCr-N系薄膜(HDCr)の評価

Effects of substrate bias frequencies on the characteristics of chromium nitride coatings deposited by pulsed DC reactive magnetron sputtering

Chromium nitride coatings have been used widely in industrial due to their good mechanical properties and corrosion resistance. In this work, the pure chromium nitride coatings were prepared by a bipolar symmetric pulsed DC reactive magnetron sputtering system at four different bias frequencies. It is observed that the texture of CrN changed from (200) to (220) as substrate bias frequencies and bias current increased. It was concluded that the high substrate bias current showed strong detrimental effects on the microstructures, adhesion and wear properties of thin films. A pure CrN thin film with sufficient hardness, adhesion and wear resistance properties combinations was achieved as deposited at a substrate bias current lower than 0.394 A in this study.

Investigation of the microstructure and characterizations of TiN/CrN nanomultilayer deposited by unbalanced magnetron sputter process

In this study, TiN, and CrN, monolayer thin films and a TiN/CrN multilayer thin film were deposited onto WC substrates by unbalance DC magnetron sputtering. Single-layer TiN and CrN thin films were prepared at various nitrogen flow rates (20–30 sccm). TiN/CrN multilayers with a monolayer thickness of 4 nm were also deposited on the WC substrates. The morphology, and crystalline structures of the as-prepared films were characterized by SEM and XRD, and their mechanical properties and thermal stabilities were also evaluated. The experimental results show that the grain size of the columnar structure increased with the nitrogen flow rate. The increase in the size of the grains in the columnar structure, however, can be minimized with an applied bias voltage of 100 V. When the nitrogen flow rate was increased from 20 to 30 sccm, β-Cr 2N transformation to CrN was observed, while the TiN structure remained unchanged. The hardnesses of the TiN and CrN thin films were ~ 23.9 and 21.4 GPa, respectively. A significant increase in the hardness of the TiN/CrN multilayer thin film to 34.9 GPa (4 nm interval) could be observed. Scratch test results also show that the multilayer has more desirable properties than the monolayers. The critical load for the TiN/CrN multilayer thin film (45.0 N) was higher than that for the TiN (~ 24.8 N) or CrN (~ 37.3 N) monolayer thin films. After annealing at 800 °C, no significant phase transformation and decrease in mechanical properties of the TiN/CrN multilayer thin film could be observed.

A study of the oxidation behavior of CrN and CrAlN thin films in air using DSC and TGA analyses

Freestanding CrN x and Cr 1 − x Al x N films with two different Al atomic percentages with respect to the metal sublattice ( x = 0.23 and x = 0.60) were produced by pulsed closed field unbalanced magnetron sputtering (P-CFUBMS). The dynamic oxidation behavior of the films has been characterized by thermal analysis using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The structure of the films at different thermal-annealing temperatures were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) in an effort to understand different phase transitions and oxidation reactions observed on the DSC curves. The peak temperatures of the main exothermic/endothermic oxidation reactions in the DSC signals at different heating rates were applied to the Kissinger model for determination of activation energies. The mechanical properties of the films at different heat-annealing states were measured by nano-indentation. It was found that the CrN x films oxidized in air after 600 °C by the dissociation of fcc (face center cubic)-CrN to h(hexagonal)-Cr 2N and nitrogen and, after 900 °C by the dissociation of h-Cr 2N to Cr and nitrogen in the film. The addition of Al to CrN film can further improve the oxidation resistance, especially for the high temperature above 800 °C. The oxidation degradation in two Cr-Al-N films started with dissociation of fcc-CrAlN to h-Cr 2N and nitrogen in the film. The presence of thermally stable Al–N bonding in the fcc-CrAlN structure can suppress the reduction of nitrogen in the film. A dense (Cr,Al) 2O 3 layer (either amorphous or crystalline) formed at early oxidation stage (< 700 °C) can act as an effective diffusion barrier slowing down the inward diffusion of the oxygen at high temperatures. Precipitation of h-AlN phase in Cr 0.77Al 0.23N and Cr 0.40Al 0.60N films were found at 900 and 1000 °C respectively, accompanied with crystalline Al 2O 3 formation. After that, both Cr-Al-N films oxidized rapidly after the dissociation of h-Cr 2N to Cr and nitrogen. In addition, Cr 0.40Al 0.60N films exhibit higher oxidation resistance than Cr 0.77Al 0.23N films. The fcc-CrAlN was retained up to 900 °C and the precipitation of h-AlN phase took place after 1000 °C in Cr 0.40Al 0.60N films. Cr 0.40Al 0.60N films also retained a hardness of 25 GPa after annealing at 800 °C in ambient air for 1 h. The activation energies of the final oxidation exothermic peaks in CrN x , Cr 0.77Al 0.23N and Cr 0.40Al 0.60N films in the current study were found to be 2.2, 3.2 and 3.9 eV atom − 1 respectively.

Finite element simulation of the effect of surface roughness on nanoindentation of thin films with spherical indenters

The effect of the surface roughness on nanoindentation results was investigated instancing a series of CrN thin films deposited by unbalanced magnetron sputtering. The arithmetic roughness (Ra) of the films ranged between 2 and 10 nm and was measured by atomic force microscopy. The measured surface topography was incorporated into a finite element model, which allowed simulating the indentation of an axisymmetric sample by a rigid spherical indenter. For the applied conditions it was found that plastic deformation could be neglected and thus purely elastic material behavior was assumed. For roughness values of Ra ≈ 2, 5, and 10 nm, 100 indents each were simulated. Subsequently, the software Elastica and the approach by Oliver and Pharr were used to evaluate Young's modulus of the CrN thin films from the simulated load-displacement curves. Under the applied conditions, the increasing roughness causes a reduction of the contact area and leads to an underestimation of Young's modulus. The mean Young's modulus of all simulated indents on the rough surfaces lies 5–14% below the Young's modulus determined for a perfectly smooth surface. This deviation seems to be independent of Ra, although the data scatter increases significantly with increasing roughness. Additionally, an influence of the lateral extension of the surface texture on the data scatter was observed which is not accounted for in roughness measures such as Ra.

Thermally induced transitions of CrN thin films

Annealing of CrN thin films in an inert atmosphere causes dissociation into Cr2N with N2 release with an activation energy, Ea, of ∼4.39 eV atom−1 in the temperature range 1000–1250 °C. At higher temperatures the Cr2N dissociates into Cr and N2 with Ea≈ 3.15 eV atom−1. These processes occur after recovery and recrystallization during which the lattice parameter decreases (from 4.162 to 4.142 A) and the mean crystallite feature size increases (from 21 to 104 nm) compared to the as-deposited values.

Effect of Interlayer on TiN and CrN Thin Films of STS 420 Hybrid-Deposited by AIP and DC Magnetron Sputtering

Effects of interlayer and the combination of different coating methods on the mechanical and corrosion behaviors of TiN and CrN coated on 420 stainless steel have been studied. STS 420 specimen were tempered at <TEX>$300^{\circ}C$</TEX> for 1 hr in vacuum furnace. The TiN and CrN thin film with 2 <TEX>${\mu}m$</TEX> thickness were coated by arc ion plating and DC magnetron sputtering following the formation of interlayer for pure titanium and chromium with 0.2 <TEX>${\mu}m$</TEX> thickness. The microstructure and surface analysis of the specimen were conducted by using SEM, XRD and roughness tester. Mechanical properties such as hardness and adhesion also were examined. XRD patterns of TiN thin films showed that preferred TiN (111) orientation was observed. The peaks of CrN (111) and <TEX>$Cr_2N$</TEX> (300) were only observed in CrN thin films deposited by arc ion plating. Both TiN and CrN deposited by arc ion plating had the higher adhesion and hardness compared to those formed by magnetron sputtering. The specimen of TiN and CrN on which interlayer deposited by magnetron sputtering and thin film deposited by arc ion plating had the highest adhesion with 22.2 N and 19.2 N. respectively. TiN and CrN samples shown the most noble corrosion potentials when the interlayers were deposited by using magnetron sputtering and the metal nitrides were deposited by using arc ion plating. The most noble corrosion potentials of TiN and CrN were found to be approximately -170 and -70 mV， respectively.