Cr Interlayer Thickness Research Articles

The effects of interlayer size and crystallinity on fatigue behavior of Cu/X (X= cr, amorphous CuZr) bilayers

In this work, interlayer (Cr vs amorphous CuZr) with various thicknesses ranging from 5 nm to 40 nm were utilized for 1000 nm-thick nanostructured Cu films on polyimide substrates. The effects of heterogeneous interface and interlayer thickness on the fatigue behavior of Cu/interlayer bilayers were investigated by in situ synchrotron X-ray diffraction, electrical resistance measurement, in combination with microstructural examinations. The results demonstrated that the fatigue tolerance highly depends on the thickness and constituent of interlayer. The fatigue lifetime monotonically increases as CuZr interlayer thickness increases, coupled to the yield stress. In contrast, the fatigue lifetime first increases and then decreases with increasing Cr interlayer thickness, reaching its maximum value at a thickness of 5 nm. The underlying mechanisms for this discrepancy can be elucidated in terms of heterogeneous constraint and interface voiding, both of which depend on the interlayer thickness.

Reprint of: Improving oxidation and wear resistance of TiB2 films by nano-multilayering with Cr

Alternating TiB2-DCMS and Cr-HiPIMS layers are used to fabricate TiB2/Cr multilayer films with varying the Cr interlayer thickness, 2 and 5 nm, and the substrate bias during growth of Cr interlayers from floating, to −60 V and −200 V. The effects of multilayer structure on mechanical properties, static oxidation, and tribological behavior of the TiB2/Cr multilayers are investigated. The results reveal that TiB2 nanocolumns renucleate at each Cr interface maintaining smooth film surface and film density. Interlaying with Cr with thicknesses of 2–5 nm improves the resistance to oxidation at 500–600 °C as compared to TiB2 monolayer. The increase of the thickness of the Cr interlayers from 2 to 5 nm decreases the hardness of the multilayer slightly but deteriorates the wear rate significantly. The friction coefficients at 500 °C are lower than those at RT due to boric acid liquid lubrication induced by surface oxidation. The TiB2/Cr multilayer films show higher wear resistance than TiB2 monolayer. The multilayer films with 2 nm-thick Cr deposited at −60 V have the lowest recorded wear rates. Irradiation with 200 eV Cr+ leads to interface mixing, resulting in the formation of B-deficient TiBx phase (x < 2) and higher wear rates compared to multilayers grown at −60 V.

Improving oxidation and wear resistance of TiB2 films by nano-multilayering with Cr

Alternating TiB2-DCMS and Cr-HiPIMS layers are used to fabricate TiB2/Cr multilayer films with varying the Cr interlayer thickness, 2 and 5 nm, and the substrate bias during growth of Cr interlayers from floating, to −60 V and −200 V. The effects of multilayer structure on mechanical properties, static oxidation, and tribological behavior of the TiB2/Cr multilayers are investigated. The results reveal that TiB2 nanocolumns renucleate at each Cr interface maintaining smooth film surface and film density. Interlaying with Cr with thicknesses of 2–5 nm improves the resistance to oxidation at 500–600 °C as compared to TiB2 monolayer. The increase of the thickness of the Cr interlayers from 2 to 5 nm decreases the hardness of the multilayer slightly but deteriorates the wear rate significantly. The friction coefficients at 500 °C are lower than those at RT due to boric acid liquid lubrication induced by surface oxidation. The TiB2/Cr multilayer films show higher wear resistance than TiB2 monolayer. The multilayer films with 2 nm-thick Cr deposited at −60 V have the lowest recorded wear rates. Irradiation with 200 eV Cr+ leads to interface mixing, resulting in the formation of B-deficient TiBx phase (x < 2) and higher wear rates compared to multilayers grown at −60 V.

Evaporation of Ti/Cr/Ti Multilayer on Flexible Polyimide and Its Application for Strain Sensor.

A flexible Ti/Cr/Ti multilayer strain gauge have been successfully developed based on polyimide substrate. The pure Ti metal strain gauge have shown the hysteresis phenomenon at the relationship between resistance and strain during tensile test. The experimental results of multilayer strain gauge show that adding Cr interlayer can improve the recovery and stability of the sensing electrode. When the interlayer Cr thickness was increased from 0 to 70 nm, the resistance decreased from 27 to 8.8 kΩ. The gauge factor (GF) value also decreased from 4.24 to 2.31 with the increase in the thickness of Cr interlayer from 30 to 70 nm, and the hysteresis phenomenon disappeared gradually. The multilayer Ti/Cr/Ti film has feasible application for strain sensor.

Effects of Cr interlayer thickness on adhesive, structural, and thermoelectric properties of antimony telluride thin films deposited by radio-frequency magnetron sputtering

We investigated the effects of Cr interlayer thickness on adhesive, structural, and thermoelectric properties of p-type antimony telluride (Sb2Te3) thin films. Prior to depositing Sb2Te3 films with a thickness of 1μm using radio-frequency magnetron sputtering, a Cr film with a thickness ranging from 0 to 216nm was deposited on a glass substrate using the same sputtering equipment. The obtained samples were thermally annealed at 300°C for 1h. Adhesiveness of the films was examined by a cross-cut method. Adhesion of Sb2Te3 thin films could be improved by incorporating the Cr interlayer, independent of the thickness of the interlayer. The surface morphology of the Sb2Te3 thin films became flat with a dense structure as the thickness of the Cr interlayer increased. Atomic composition analysis indicated that Te atoms might be diffused into the Cr interlayer and formed Cr-based alloys when the Cr interlayer thickness was increased to >100nm. X-ray diffraction analyses indicated that the crystal orientation, crystallite size, and strain of the films reached their maximum values at Cr interlayer thicknesses of 46–70nm. Thermoelectric properties of the films were improved by incorporating the Cr interlayer of appropriate thickness. In particular, a power factor of 18.7μW/(cmK2) was achieved at a Cr interlayer thickness of 46nm, which was approximately 4 times larger than that of the film with no Cr interlayer.

Effects of interlayer thickness and the substrate material on the adhesion properties of CrZrN coatings

To confirm the influence of the interlayer thickness and substrate material on adhesion properties, CrZrN coatings with various Cr interlayer thickness were deposited on AISI H13, high speed steel, and tungsten carbide using unbalanced magnetron sputtering. The adhesion strength showed maximum value at 300 nm of the interlayer, but as the interlayer increased further to 450 nm, the adhesion strength decreased. The adhesion properties of the coatings were dependent upon not only interlayer thickness but also the substrate materials. The adhesion strength of the coating were measured 12, 32, 53 N on the tungsten carbide, AISI H13 steel, high speed steel, respectively and three different failure modes such as buckling spallation, wedging spallation, and chipping were observed on each substrate. The difference in adhesion properties could be attributed to the difference in value of elastic strain to failure (H/E) among the CrZrN coating, the interlayer, and the substrates material.

Effect of the Thickness of Cr Interlayer on the High-Frequency Characteristics of FeCoTa/Cr/FeCoTa Multilayers

The effect of non-ferromagnetic Cr interlayer on the high-frequency ferromagnetic properties (HFFMPs) was investigated by use of FeCoTa/Cr/ FeCoTa triple layered films. In conventional thought, the metal interlayer gives rise to a high eddy current loss and therefore a deteriorated HFFMP. However, it is found that HFFMPs depend on the thickness of Cr interlayer. The HFFPMs are improved by Cr-interlayer with a thickness less than 12 nm (sample C1). Comparing with the Cr-interlayer-free FeCoHf single layered film (sample C0), the magnetic anisotropy field of C1 dramatically increases from 185 Oe for C0 to 558 Oe for C1. As a consequence, a high ferromagnetic resonance frequency over than 3 GHz is achieved for sample C1. When the thickness of Cr-interlayer is more than 120 nm (C2), the HFFMPs are reduced due to the increase of eddy current loss and magnetic decoupling between the ferromagnetic layers.

Effect of chromium interlayer on magnetic exchange coupling of SmCo/Cr/TbFeCo multilayer thin films

A series of SmCo/Cr/TbFeCo multilayer thin films with perpendicular anisotropy were prepared by RF-magnetron sputtering system, and the effects of Cr interlayer thickness on magnetic properties and interlayer exchange coupling were investigated. It was found that the magnetic properties varied with the thickness of Cr interlayer, especially the values of saturation magnetization M s and the coercivity H c fluctuated periodically with the thickness of Cr interlayer. STM images revealed that the variation of coercivity H c was attributed to the microstructure change of SmCo layer influenced by Cr interlayer, and the variation of M s was related to interlayer exchange coupling.

Magnetic Properties of (Sm, Tb)FeCo/Cr/TbFeCo Trilayers with Perpendicular Anisotropy

A series of (Sm, Tb)FeCo/Cr/TbFeCo trilayers with perpendicular anisotropy was prepared by RF magnetron sputtering, and the effect of Cr interlayer thickness on magnetic properties and interlayer exchange coupling was investigated. All the samples showed strong out-of-plane anisotropy but their hysteresis loops displayed two types: single-phase and double-phase, indicating that interlayer exchange coupling and magnetic properties varied with the thickness of Cr interlayer. Both saturation field H s and (1- M r/ M s) curves indicated that interlayer exchange coupling oscillated between antiferromagnetic and ferromagnetic with a period of 1.6 nm, and the oscillation strength attenuated with increasing Cr interlayer thickness. After being annealed at 450 °C for 25 min, the hysteresis loops of all the samples became single-phase type and coercivity H c decreased greatly, which could be attributed to the decrease of effective anisotropy in (Sm, TbFeCo) grains.

New interface solution for Ni/Ti multilayers

Nickel/titanium multilayers (ML) and supermirrors (SM) were fabricated by DC magnetron sputtering on glass or Si (1 0 0) substrates. It was possible to increase the reflectivity of ML and SM by the deposition of an ultrathin Cr layer at the Ni/Ti interfaces. Interdiffusion decreases when the Ni and Ti are separated by a covering Cr layer (3 Å), whereas, in the range where the Cr interlayer thickness is higher than the Ni/Ti interdiffusion depth (approximately 6 Å) or the surface roughness, the growth of a closed Cr layer is prohibited reducing the reflectivity. The presence of a 10 Å Cr interlayer on some Ti layers also results in enhanced reflectivities due to a smoothing effect of the interface for the following layers. The reflectivities of two monochromators for q z = 0.069 Å and a bandwidth (Δ λ/ λ) of 6% and 12% reach a value of approximately 0.90.

X-ray residual stress analysis on CrN/Cr/CrN multilayer PVD coatings deposited on different steel substrates

Hard physical vapour deposition (PVD) coatings as CrN, TiN and NbN have been successfully exploited for wear and corrosion protection. One limit to their performances under service is caused by the presence of large residual stresses, which adversely affect their properties as fatigue, fracture, corrosion, friction and wear resistance. X-ray diffraction (XRD) has been used for measuring residual stress on CrN/Cr/CrN multilayer coatings, produced by cathodic arc evaporation on substrates of three different steels (AISI H 13, AISI 1040 and K340). The thickness of the external and internal CrN layer was 1.6 μm in all the samples, while three thicknesses of the intermediate Cr layer, respectively, 0.5, 1.0 and 1.6 μm were used. The stress along two perpendicular directions ( ϕ = 0°, 90°) on the coating surface have been measured by recording the peak positions of CrN {111} reflection for each ϕ at different tilt angles ψ. Regardless of the type of steel employed as substrate, residual compressive stresses are present in the external CrN layers. Furthermore, the results reveal stress anisotropy ( σ ϕ=0° ≠ σ ϕ=90° ) in the coating plane. In the coatings deposited on AISI 1040 steel stress is more isotropic independently on the Cr interlayer thickness.

Deposition of CrN–MoS 2 thin films by D.C. magnetron sputtering

As technology advances, there is a demand for development of hard, solid lubricant coatings. CrN–MoS 2 films were deposited on SKD 11 tool steel by co-deposition of MoS 2 with CrN using a D.C. magnetron sputtering process. The influence of the Cr interlayer thickness, the N 2/Ar inlet gas ratio, the deposition temperature, the amount of MoS 2 in the film, and the bias voltage on the mechanical and the structural properties of the films were investigated. The critical load increased with the increase of the Cr interlayer thickness. The hardness of the film increased with the decrease of nitrogen content in the gas and with the increase of the deposition temperature. The films show less crystallinity with the increase of the MoS 2 content in the films. The hardness of the film reached maximum level at the negative substrate bias potential of −100 V and decreased with a further increase of the bias potential. The thickness of the film remained the same with the increase of the bias voltage.

Interfacial Sensitivity and Zero-Bias Anomalies in Magnetic Tunnel Junctions

Large zero-bias resistance anomalies as well as an extremely strong decrease of magnetoresistance were observed in Co/Al2O3/Co magnetic tunnel junctions with thin Cr interfacial layers. The tunnel magnetoresistance decays exponentially with nominal Cr interlayer thickness with a length scale of ∼0.1 nm. The magnetoresistance decay, as well as some aspects of the zero-bias anomalies, can be understood by considering a strong spin-dependent modification of the density of states at Co/Cr interfaces and existing models for zero-bias anomalies. The effect of the density of states modification is also observed in the transport of the metallic electrodes alone, confirming the key role of the Co/Cr interface. However, several aspects of the zero-bias anomalies cannot be explained at present, suggesting perhaps a novel form of the Kondo resonance.

Interfacial Sensitivity and Zero-Bias Anomalies in Magnetic Tunnel Junctions

Large zero-bias resistance anomalies as well as an extremely strong decrease of magnetoresistance were observed in Co/Al 2 O 3 /Co magnetic tunnel junctions with thin Cr interfacial layers. The tunnel magnetoresistance decays exponentially with nominal Cr interlayer thickness with a length scale of ∼ 0.1 nm. The magnetoresistance decay, as well as some aspects of the zero-bias anomalies, can be understood by considering a strong spin-dependent modification of the density of states at Co/Cr interfaces and existing models for zero-bias anomalies. The effect of the density of states modification is also observed in the transport of the metallic electrodes alone, confirming the key role of the Co/Cr interface. However, several aspects of the zero-bias anomalies cannot be explained at present, suggesting perhaps a novel form of the Kondo resonance.

Interfacial density of states in magnetic tunnel junctions.

Large zero-bias resistance anomalies as well as a collapse of magnetoresistance were observed in Co/Al2O3/Co magnetic tunnel junctions with thin Cr interfacial layers. The tunnel magnetoresistance decays exponentially with nominal Cr interlayer thickness with a length scale of approximately 1 A more than twice as fast as for Cu interlayers. The strong suppression of magnetoresistance, as well as the zero-bias anomalies, can be understood by considering a strong spin-dependent modification of the density of states at Co/Cr interfaces. The role of the interfacial density of states is shown by the use of specially engineered structures. Similar effects are predicted and observed in junctions with Ru interfacial layers.

Effects of thin Cr interlayer on time decay of magnetization and magnetization reversal for CoCrTaPt thin film media

The effect of thin Cr interlayer on the time decay of magnetization and magnetization reversal for CoCrTaPt/Cr/CoCrTaPt media is presented. The time decay of magnetization was measured at various reverse magnetic fields. The maximum magnetic viscosity coefficient which occurs around the remanent coercivity increases with increasing interlayer thickness, which implies the degradation of thermal stability. The activation volume decreases with increasing Cr interlayer thickness. Both torque magnetometer and the law of approach to saturation methods were used to measure the magnetic anisotropy. The results show a decrease in anisotropy with increasing interlayer thickness which may explain the degradation of thermal stability. The distribution of rotational hysteresis losses (W/sub r/) were measured and the rotational hysteresis integral (R/sub h/) was found to decrease with increasing Cr interlayer thickness which may be caused by reduction of the magnetic interaction.

Variety of interlayer coupling in sandwiches

The possible mechanisms of magnetic interlayer coupling in sandwiches has been analyzed on the basis of experimental data of coercive force, domain structure and microstructure of Fe 15Co 20Ni 65/Cr/Fe 15Co 20Ni 65 and Fe 19Ni 81/Cr/Fe 19Ni 81 films. By means of theoretical estimations we have shown that with increasing Cr interlayer thickness ( L) the exchange interlayer coupling changes into a magnetostatic interaction which is due to either the interface roughness or the magnetization ripple for different L.

Bilinear and Biquadratic Exchange Coupling in Fe(110)/Cr/Fe Trilayers

ABSTRACTThe indirect exchange coupling in W(110)/Fe/Cr/Fe/Cr trilayers was determined by analysis of magnetization curves measured by Kerr magnetometry. We adjusted the uniaxial in-plane anisotropies in the two Fe layers in such a way that the easy axes were orthogonal, [001] in the 1st, [110] in the 2nd layer. This allows an independent determination of both bilinear (i) and biquadratic (J2) coupling constants. We determined tJ and J2 as a function of Cr interlayer thickness (tcT = 0 – 4 nm), preparation temperature of the interlayer Tcr=100 – 500 K, and as a function of temperature (T = 100 – 300 K). Results for the exchange coupling are correlated to the particular lateral thickness fluctuation of the Cr spacer.

Effect of a Cr interlayer on properties of CoCrTa/Cr media: experiments and simulations

An experimental result and a micromagnetics model of a double layered CoCrTa film separated by a thin flash Cr interlayer are described. In the experiment, coercivity and coercivity squareness drastically changed with an increase in the Cr interlayer thickness. There was some coercivity increase in the double layered films compared to a single layered film when the flash Cr interlayer thickness was around 8 /spl Aring/ to 10 /spl Aring/ and coercivity decreased with further increase of the Cr interlayer thickness up to 50 /spl Aring/. At a very thin interlayer range, the change of coercivity is affected mainly by the change of exchange interaction. By using the assumption of the formation of a Cr island type interlayer at a thin interlayer region, we can explain the increment of coercivity at the initial state.

Noncollinear and collinear magnetic structures in exchange coupled Fe/Cr(001) superlattices.

The magnetic and structural properties of molecular beam epitaxy grown Fe/Cr(001) superlattices were studied as a function of the growth temperature ${\mathit{T}}_{\mathit{g}}$ using polarized neutron reflectometry (PNR) with polarization analysis, magneto-optic Kerr effect (MOKE), and x-ray-scattering techniques. From MOKE and PNR as a function of external field we find strong noncollinear coupling between the Fe layers and a so far unexpected coupling angle of 50\ifmmode^\circ\else\textdegree\fi{} near remanence for a sample grown at ${\mathit{T}}_{\mathit{g}}$=250 \ifmmode^\circ\else\textdegree\fi{}C. A detailed discussion of the domain structure of the sample near remanence confirms the modeling. On the other hand, an otherwise equivalent sample grown at room temperature exhibits completely ferromagnetic or uncoupled behavior. Using diffuse x-ray-scattering methods these distinct differences in the magnetic structure are found to be correlated with a growth temperature dependent length scale of constant Cr interlayer thickness ${\mathit{l}}_{\mathrm{Cr}}$. We find that ${\mathit{l}}_{\mathrm{Cr}}$ increases significantly with ${\mathit{T}}_{\mathit{g}}$. These results are discussed in the framework of current theories of noncollinear exchange. It is demonstrated that the bilinear-biquadratic formalism used so far is inconsistent with the data. The Cr specific proximity magnetism model is discussed which explains the occurrence of noncollinear coupling for systems with Cr interlayer thickness fluctuations on the length scale observed here for ${\mathit{T}}_{\mathit{g}}$=250 \ifmmode^\circ\else\textdegree\fi{}C. The model yields an exchange energy different from the bilinear-biquadratic formalism used so far, explaining the asymptotic approach to saturation observed by MOKE.