Bilayer Period Research Articles

Adhesion layers between piezoelectric and magnetostrictive layers in a MEMS magneto-sensor stack: Influence on the phase transformation of deposited Co/Fe multilayers to magnetostrictive CoxFe1−x phase

Magnetoelectric MEMS devices, such as magnetic field sensors, may be composed of a multilayer stack as a magnetostrictive layer, which is mechanically coupled to a piezoelectric film. Good adhesion and a stable rigid interface have to be maintained for such a sensor. Certain electric and magnetic properties, especially the magnetostriction, have to reach sufficiently high values, which can be achieved by selected phases or mixtures of phases. In this study, Co/Fe multilayers with varied bilayer periods are deposited onto AlN or Sc0.14Al0.86N coated Si substrates by DC magnetron sputtering with the optional insertion of a 5 nm thick adhesion layer of Cr or Zr to investigate its influence on the formation of the desired mixture of bcc and fcc Co0.7Fe0.3 phases, which are expected to yield a high magnetostrictive strain, after an RTA at 800 °C. A qualitative phase analysis is made by XRD in Bragg-Brentano geometry and shows that the bcc + fcc mixture can be achieved with a Cr interlayer. A sharp, void free, and undamaged interface for that case was observed in SEM images of cross sections prepared with FIB.

Microstructural and mechanical properties of TiN/CrN and TiSiN/CrN multilayer coatings deposited in an industrial-scale HiPIMS system: Effect of the Si incorporation

Surface engineering through the deposition of advanced coatings, particularly multilayer coatings has gained significant interest for enhancing the performance of coated parts. The incorporation of Si into TiN coatings has shown promise for improving hardness, oxidation resistance, and thermal stability, while high-power impulse magnetron sputtering (HiPIMS) has emerged as a technique to deposit coatings with exceptional properties. However, TiN/CrN and TiSiN/CrN coatings deposited by HiPIMS remain relatively unexplored. In this study, different TiN/CrN and TiSiN/CrN multilayer coatings with different bilayer periods from 5 to 85 nm were deposited using an industrial-scale HiPIMS reactor, and their microstructure and mechanical properties were investigated using advanced characterization techniques. Results revealed successful deposition of smooth and compact coatings with controlled bilayer periods. X-ray diffraction analysis showed separate crystalline phases for coatings with high bilayer periods, while those with smaller bilayer periods exhibited peak-overlapping and superlattice overtones, especially for the TiN/CrN coatings. Epitaxial grain growth was confirmed by high-resolution transmission electron microscopy (HRTEM). HRTEM and electron energy-loss spectroscopy measurements confirmed Si incorporation into the TiN crystal lattice of TiSiN/CrN coatings reducing the crystallinity, especially for coatings with smaller bilayer periods. Nanoindentation tests revealed that coatings with a bilayer period of 15–20 nm displayed the highest hardness values regardless of the composition. The mechanical properties of the TiSiN/CrN coatings showed no improvement over those of the TiN/CrN coatings, attributed to the Si induced amorphization of the Ti(Si)N phase and the absence of SiNx phase segregation within the TiN nanocrystals in these coatings. These findings provide valuable insights into the microstructure and mechanical properties of TiN/CrN and TiSiN/CrN multilayer coatings deposited by HiPIMS in an industrial scale reactor, paving the way for their application in various industrial sectors.

Bilayer period and ratio dependent structure and mechanical properties of TiN/MoN superlattices

Transition metal nitrides are widely used in the hard materials and protective coatings industry, but are limited by their low fracture toughness. Encouraged by previous studies on remarkable simultaneous improvements in strength and ductility through superlattice (SL) architectures, various TiN/MoN SL thin films were developed on MgO (100) substrates. By varying their bilayer periods (Λ) between 2 and 23 nm with bilayer ratios (Γ = ℓMoN:ℓTiN) of 0.5, 1, 2, and 2.7, their individual effects on structure and mechanical properties can be revealed. All SLs—independent of Λ, Γ, and nitrogen-to-metal (N/Me) ratio (within the analysed variations)—exhibit a rocksalt structure with high-order satellite peaks in X-ray diffraction. While the SLs with Γ = 2 have the lowest hardness (H)—presumably due to their overall lowest N/Me ratio—the SLs with Γ = 2.7 are the hardest with a neat superlattice effect. The SLs with Γ = 1 and 2.7 have a comparable superlattice effect on fracture toughness (KIC), peaking at Λ = 9.9 and 9.3 nm, respectively. Of all the SLs investigated, those with Γ = 1 provide the best blend of mechanical properties and dry sliding coefficient of friction (µ), such as H = 34.8±1.6 GPa, KIC = 4.1±0.2 MPa√m, and µ = 0.27 when Λ = 9.9 nm. Deepening current understanding of superlattice effects in general—particularly the influence of bilayer periods and ratios—in relation to the nitrogen supply and heterogeneous microstructures, our study accelerates the design of nanolayered coatings with desired structure-property combinations.

Electroplating of Palladium‐Based Integrated Reactive Multilayer Systems (iRMS)

Bonding with integrated reactive material systems enables joining of heterogeneous substrates at room temperature. The increasing diversity of electronic modules raises the demand for low temperature bonding processes for heat sensitive components. In this article, fundamental steps for the deposition of Pd/In multilayers from a single bath electrolyte are presented. It furthermore describes the deposition of Pd/Sn reactive multilayers for bonding application on ceramic substrates and introduces a new semi‐automated plating tool for Pd/Sn multilayers. The Pd/Sn multilayers can be deposited reproducible on silicon and ceramic substrates. While a bilayer period of 425 nm enables stable ignition and bonding of Si substrates, the bilayer period for ceramics has to be increased to 620 nm to compensate the higher heat dissipation into the substrate. By integrating 2.5–9 μm thick Sn compensation layers beneath the integrated reactive multilayer systems (iRMS) to smoothen the surface profile of the printed metallization and improved bonding processes with wedge compensation, a homogeneous bond along the whole interface can be achieved.

Impact of substrate thickness and surface roughness on Al/Ni multilayer reaction kinetics

Reactive multilayers comprising alternating nanoscale layers of Al and Ni, exhibit potential across various applications, including localized heating for welding and joining. Control over reaction properties is pivotal for emerging applications, such as chemical time delays or neutralization of biological or chemical weapons. This research offers insights into the intricate interplay between substrate thickness, surface roughness, and the behavior of Al/Ni reactive multilayers, opening avenues for tailored applications in various domains. To observe this interplay, silica with various thicknesses from 0.4 µm to 1.6 µm was deposited on polished single crystalline Si and rough poly‐Si base substrates. Additionally, to analyze the impact of varying silica thickness along the sample length on reaction behavior, silica in step‐like shape was fabricated. Subsequently, Al/Ni multilayers with 5 µm total thickness and 20 or 50 nm bilayer periodicities were deposited. Reaction velocity and temperature were monitored with a high‐speed camera and pyrometer. Results indicate that silica thickness significantly affects self‐propagation in multilayers. The reaction is not self‐sustained for silica layers ≤ 0.4 µm, depending on bilayer periodicity and substrate roughness. The velocity increases or decreases based on the direction of reaction propagation, whether it moves upwards or downwards, in relation to the thickness of silica.This article is protected by copyright. All rights reserved.

Mechanical properties of VC/ZrC and VC/HfC superlattices

Face-centered cubic transition metal carbides exhibit high melting points and hardness, making them prominent candidates for protective coating applications. Vanadium carbide (VC) has typical characteristics of transition metal carbides. It serves as model material in this study, in which we showcase the effect of superlattice architecture on mechanical properties and fracture toughness. While beneficial effects of superlattice arrangement have been demonstrated for a series of nitride-based coatings, transition metal carbides remain largely unexplored territory. Following density functional theory based ab initio predictions on lattice and shear modulus mismatch, we develop VC/ZrC and VC/HfC superlattice coatings synthesized via pulsed DC sputter deposition. The bilayer periods (Λ) of our fully fcc-structured polycrystalline coatings range between 2–50 nm (indicated by X-ray diffraction, transmission and scanning electron microscopy). The chemical composition is close to 1:1 stoichiometry (from X-ray fluorescence, elastic back-scattering spectrometry and elastic recoil detection analysis). Both superlattice series exhibit a strong dependence of hardness, elastic modulus, and fracture toughness on their bilayer periods, which can only be correlated with the in-plane stress variations for VC/ZrC. The VC/HfC superlattices provide their peak-hardness of 36.0 ± 1.6 GPa for Λ = 6 nm and their peak in fracture toughness of 3.5 ± 0.5 MPa√m for Λ = 10 nm.

Hardness and fracture toughness enhancement in transition metal diboride multilayer films with structural variations

The simultaneous enhancement of hardness (H) and fracture toughness (KIC) through the formation of superlattice structures challenges the conventional belief that these quantities are mutually exclusive. Here, this approach has been applied to the transition metal diborides, whose inherent brittleness severely restricts their application potential. The mechanical properties of TiB2/TaB2 systems as a function of bi-layer period Λ are investigated, combining theoretical and experimental approaches. Density Functional Theory is used to investigate the structural stability and mechanical properties of stoichiometric hexagonal TiB2/TaB2 superlattices for Λ = 3.9 – 11.9 nm. The calculations predict the highest H = 38 GPa and KIC (100) of 3.3 MPa.m1/2 at the value of Λ = 5.2 nm. Motivated by the theoretical results, multilayer films with Λ = 4–40 nm were prepared by direct current magnetron sputtering. Due to the sputtering effects, the deposited diboride films differ significantly from the view of stoichiometry and structure. A detailed structure investigation reveals TiB2/TaB2 in form of superlattices exhibiting coherent interfaces for Λ = 4 nm. For higher Λ, parts of TaB2 layers transform from the crystalline to the disordered phase. These transformations are reflected in the mechanical properties as measured by nanoindentation and micromechanical bending tests. The evolution of hardness follows Hall-Petch behavior, reaching a maximum of 42 GPa at Λ = 6 nm. Enhancing fracture toughness involves more complex mechanisms resulting in two KIC maxima: 3.8 MPa.m1/2 at Λ = 6 nm and 3.7 MPa.m1/2 at Λ = 40 nm.

Preparation and tribological properties of Ni/DLC multilayer film

Ni was selected as a transition layer and sublayer in the diamondlike carbon-based multilayered film with varied bilayer periods (from 228 to 970 nm) prepared by magnetron sputtering. The reaction between Ni- and C-containing particles was discussed, and the influences of bilayer periods on the structure and morphology, accompanied with the frictional behaviors at different loading forces (2 and 5 N), as well as the field emission properties were investigated. The results showed that Ni grew in the (111) plane, and there was no Ni–C bond or graphene formed in the film because of the relatively lower energy during deposition. Moreover, the content of sp2C in the film, the hardness, and the field emission performance exhibited an initial increase followed by a subsequent decrease with increasing bilayer periods. However, the frictional coefficient decreased owing to more graphitization with an increase of the applied load. Particularly noteworthy was that the film possessed a bilayer period of 710 nm, displayed a compact structure with a smaller grain size, and showed reduced sp2C content in the role of Ni. This resulted in sustained lower surface roughness, heightened hardness, decreased coefficient of friction, and a smaller opening electric field.

Structure and mechanical properties of TiCN-ZrCN multilayer coatings

The present study is focused on the design, deposition and characterization of nanoscale multilayer TiCN/ZrCN coatings obtained by cathodic-arc PVD technique. The multilayer coatings with the bilayer period’s thickness of 12 nm, 20 nm and 32 nm were deposited on stainless steel and high-speed steel substrates at temperature of 320°C in a mixture of N2 and CH4 gases. Scanning electron microscopy equipped with energy dispersive x-ray spectroscopy, was employed to investigate the top surface morphology, cross-sectional morphology, bilayer thickness and structure of the coatings. Mechanical properties were investigated via Calotester, Nanoindentation tester, Scratch tester and Tribometer. The SEM/EDS cross-sectional analysis revealed a columnar morphology and well expressed multi-layered periodic structure. All the multilayer samples demonstrated an increase in hardness and well fracture resistance ability in comparison to TiCN and ZrCN monolayer coatings. The highest nanohardness of 41GPa and better wear resistance for the coatings with bilayer period of 12 nm was determined. The results of the study show that a reduction in the thickness of the individual sub-layers has a significant impact on the mechanical properties of the coatings.

Interface-dominated deformation mechanisms in Cr/CrN/Cr-DLC multilayer triggered by nanoindentation

The diamond-like carbon (DLC) film traditionally possesses low toughness owing to high intrinsic compressive stress. The incorporation of other elements into the DLC film provides an effective approach to improving toughness, but it is still limited and produces some detrimental effects. In this study, a new strategy of designing the Cr/CrN multilayers to serve as a functional transition layer and doping Cr into DLC film is attempted to simultaneously improve the strength and ductility of DLC film. Herein, a profound understanding of the deformation mechanisms of Cr/CrN/Cr-DLC multilayers with different bilayer periods (BPs) during the indentation process is investigated. The maximum strength and toughness values are achieved by the Cr/CrN/Cr-DLC multilayer with BP of 10 nm (P10). The cooperation of multiple strengthening mechanisms involving the diminishment of dislocation motion within individual layers and the formation of coherent twin boundaries (CTBs) and Lomer-Cottrell locks (L-C locks) contributed significantly to the high hardness of P10. The predominant toughening mechanism of P10 is the formation of a substantial number of high-density stacking faults (SFs) in CrN sublayers, which is attributed to that the pre-existed CTBs with numerous kinks in CrN can reduce the stacking fault energies (SFEs) for P10. Few deformation twins facilitated the deformation of P10. In contrast, a versatile deformation mechanism appears in Cr/CrN/Cr-DLC with BP of 100 nm (P100) involving dislocation motion, SFs, deformation twins, and, of particular note, amorphization. However, the released energy related to deformation in P100 is limited, leading to cracks in the Cr-DLC top layer. This multilayer structure can provide additional strengthening and toughening mechanisms to endow the DLC film with profound mechanical properties in harsh service conditions.

Influence of Bilayer Thickness on Mechanical and Tribological Properties of (Ti-Al)N/MoN Nanostructured Hard Coatings Deposited by Cathodic Arc Ion Plating

Deposition of (Ti-Al)N/MoN multilayered coatings was carried out through a cathodic ion-plating system in an argon and then nitrogen atmosphere. Bilayer thickness (Λ) of all the samples were achieved, from 22 to 104 nm, by organizing substrate holder rotational speed (SRS). To obtain the optimum properties of the (Ti-Al)N/MoN coatings, the Ti and Al ratio was maintained at a level of 1:1. X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy were utilized to analyze the crystal structure and morphology of the coatings. Mechanical and tribological properties were examined by nanohardness and atomic force microscopy (AFM). The preferred orientation of the (Ti-Al)N/MoN nanoscale multilayer films was TiAlN (200) and MoN (200), which had face centered cubic (fcc) and hexagonal structures, respectively. The hardness increased with the decrease in Λ (104 nm to 26 nm), and then it increased. The highest hardness of 37 GPa was revealed at Λ = 26 nm, whereas the least wear rate of 8.09 × 10−7 mm3/N.m was attained at Λ = 22 nm. Wear rate, roughness, and coefficient of friction were decreased with decreasing bilayer period. EDS results showed that Al and Ti contents were almost the same in all samples, as per design of the experiment.

Unraveling the superlattice effect for hexagonal transition metal diboride coatings

Superlattice structures enable the simultaneous enhancement in hardness (H) and fracture toughness (KIC) of ceramic-like coatings. While a deeper understanding of this effect has been gained for fcc-structured transition metal nitrides (TMN), hardly any knowledge is available for hexagonal diborides (TMB2). Here we show that superlattices can—similarly to nitrides—increase the hardness and toughness of diboride films. For this purpose, we deposited TiB2/WB2 and TiB2/ZrB2 superlattices with different bilayer periods (Λ) by non-reactive sputtering. Nanoindentation and in-situ microcantilever bending tests yield a distinct H peak for the TiB2/WB2 system (45.5 ± 1.3 GPa for Λ = 6 nm) but no increase in KIC related to a difference in shear moduli (112 GPa). Contrary, the TiB2/ZrB2 system shows no peak in H, but for KIC with 3.70 ± 0.26 MPa∙m1/2 at Λ = 4 nm originating from differences in lattice spacing (0.14 Å), hence causing coherent stresses retarding crack growth.

High density of stacking faults strengthened TaN/TiN multilayer

Multilayer coatings with individual layer thickness on the nanoscale exhibit superior mechanical properties because of their high interface density. However, compared to artificial phase interfaces, planar defects like twin and stacking faults (SFs) are hardly investigated in ceramic multilayer systems. We choose to combine the group VB transition metal nitride (TMN) TaN with its extremely low stacking faults energy (SFE) and TiN to form a superlattice (SL). TiN/TaN multilayers with a bilayer period (Λ) from 8 nm to 100 nm were prepared by dc magnetron sputtering. These as-deposited films show a peak hardness 36 ± 2.4 GPa at Λ=20 nm. The extensive high-resolution transmission electron microscopy (HRTEM) observations reveal that the dissociation of full dislocations results in the network of SFs and the formation of Lomer-Cottrell lock arrays inside the TaN layer. Meanwhile, further dislocation analysis indicated the Shockley partials cross slip at the interface. These findings provide us with a new perspective for designing TMN multilayers with planar defects.

Development of TaC-based transition metal carbide superlattices via compound target magnetron sputtering

Transition metal carbides belong to ultra-high temperature ceramics and are particularly valued for their high thermal and mechanical stability as well as melting points of even above 4000 °C. However, a considerable limitation of these materials is their high inherent brittleness. Inspired by the success of nanolayered superlattice architecture—shown to enhance both hardness and toughness of transition metal (TM) nitrides—we developed superlattice films with TM carbides. Among these, density functional theory calculations suggest TaC/HfC and TiC/TaC to have a similar shear modulus mismatch of 23 and 19 GPa, but a different lattice parameter mismatch of 4.2 and 2.4%, respectively. Detailed transmission electron microscopy and X-ray diffraction show a pronounced superlattice structure for TiC/TaC with nominal bilayer periods Λnom of 2, 6, and 10 nm. Contrary, the TaC/HfC showed a more solid solution like characteristic for Λnom = 2 nm, and a clear superlattice structure for Λnom = 6 and 10 nmjap. While the hardness of the TaC/HfC coatings is between those of their constituents TaC (33.3 ± 1.9 GPa) and HfC (37.4 ± 3.2 GPa), the TiC/TaC superlattices outperform their constituents and clearly show a superlattice-effect with a peak of 44.1 ± 3.4 GPa at Λnom = 2 nm (TiC has 37.6 ± 3.1 GPa). Also the qualitative fracture behavior investigation with 450-mN-loaded cube corner indentation yield the TiC/TaC superlattices to be superior to the TaC/HfC as well as the monolithically prepared TiC, TaC, and HfC coatings.

A comparative study of nanolaminate CrN/Mo2N and CrN/W2N as hard and corrosion resistant coatings

Nanolaminate coatings (NLC) consisting of alternated CrN coupled with either cubic tungsten nitride (β-W2N) or molybdenum nitride (γ-Mo2N) were deposited on cold worked tool steel substrates using reactive DC reactive magnetron sputtering for improved mechanical and corrosion resistance. The CrN/γ-Mo2N and CrN/β-W2N nanolaminate systems were found to perform better than the corresponding single-layer systems, with both mechanical and electrochemical properties improving by decreasing the individual layer thickness from 100 to 5 nm. The CrN/β-W2N NLC combined the high hardness value of W2N with the low corrosion current of CrN. The CrN/γ-Mo2N NLC showed synergistic improvements consisting of both higher hardness and lower corrosion currents with respect to the constituent materials alone. The dependence of mechanical and corrosion properties on the bilayer period is discussed in terms of the grain size, residual stresses and texture of the constituent materials and the nanostructured character of the multilayer architecture.

Microstructure and high-temperature tribological characteristics of self-lubricating TiAlSiN/VSiN multilayer nitride coatings

In recent years, self-lubricating hard protective coatings operated at elevated temperature have drawn great amount of attentions. It has been found that alloying certain elements such as vanadium is an effective method to reduce the friction coefficient, since the Magnéli phase formed at elevated temperature provides a self-lubricious surface during the wear process. However, the formation kinetics of the Magnéli phase should be appropriately controlled. Insufficient or excessive amount of Magnéli phase formation may result in high friction coefficient or severe oxidation of coatings. This study reports an architectural design strategy to engineer the mechanical and high temperature tribological properties of TiAlSiN/VSiN multilayer.In this study, the multilayer system exhibited a low friction coefficient of 0.28 and the lowest wear rate of 7.01 × 10−6mm3N−1m−1 was revealed at multilayer with bilayer period of 16 nm during the wear test at 700 °C. The existence of the Magnéli phase, V2O5, was observed by XPS and its high-temperature lubricating effect was revealed as compared to the wear test at room temperature. It is demonstrated that a particular architectural design of TiAlSiN/VSiN multilayer coating provides a potential candidate for high-speed cutting tools due to their mechanical and lubricious properties.

Role of ZnO and MgO interfaces on the growth and optoelectronic properties of atomic layer deposited Zn1−xMgxO films

Zn1−xMgxO films with very precise Mg content are of strong interest for the development of buffer layers on copper-indium-gallium-sulfide solar cells. Atomic layer deposition (ALD) has been successfully used for buffer layers with appropriate electronic properties; however, a good understanding of the growth properties of the ternary oxide is still lacking. Here, we investigate the role of the ZnO/MgO interface on the growth and resulting optoelectronic properties by varying the supercycle parameters (pulse ratio and bilayer period) of the ALD process. We demonstrate that the growth of the MgO layer is enhanced by the ZnO surface, describing the interplay between ZnO and MgO interfaces on the growth of Zn1−xMgxO films. The optical properties of the film not only depend on the Mg content but also on the bilayer period at a given Mg content. More specifically, the bandgap for a given Mg composition is high for the smallest bilayer period 5, starts decreasing slightly for bilayer periods between 10 and 20 due to the increase in thickness of the ZnO layer and confinement effects, and falls to a bandgap of ZnO as the bilayer period increases further >40. With the change in Zn1−xMgxO films from well-mixed to multilayer material as the bilayer period is varied, we illustrate that the optical properties of Zn1−xMgxO can be tuned effectively without largely altering the composition. Probing the effect of the bilayer period on the ternary oxides by ALD is a useful tool in understanding the mixing and interplay of binary materials that can be applied for many other materials.

A novel ReN/TiAlN multilayer coating on M2 steel by magnetron sputtering: Development and electrochemical behavior

By DC magnetron sputtering ReN and multilayers of TiAlN/ReN films were produced. The coatings were deposited onto high-speed steel (AISI M2) samples and silicon wafers. Analysis of the microstructure and phase composition showed that the ReN monolayer, which was the same as the coating used subsequently for the manufacture of the multilayers of TiAlN/ReN, possessed a cubic crystalline structure. The ReN coating had preferential columnar growth in the direction of the plane (111) and presented precipitates of the rhenium oxides ReO2 and ReO3. A detailed study of the electrochemical behavior and corrosion resistance of the coated steel substrate as a function of the number of TiAlN/ReN bilayers was carried out using electrochemical impedance spectroscopy and polarization measurements. The coatings exhibited a relative high hardness and Young's Modulus, and a better performance against corrosion in aqueous media rich in chlorine ions when the bilayer number and period were 5 and 221.2 nm, respectively. It was observed that the formation of rhenium oxide particles influences the electrochemical behavior of coatings.

Mechanical Properties and Thermal Stability of CrZrN/CrZrSiN Multilayer Coatings with Different Bilayer Periods

The CrZrN/CrZrSiN multilayer coatings at a bilayer period range decreasing from 1.35 μm to 0.45 μm were synthesized on a Si (100) wafer and WC-6 wt.% Co substrate using a closed-field unbalanced magnetron sputter, and the thickness effects on the mechanical properties and thermal stability were investigated. The CrZrN/CrZrSiN multilayer coatings showed high hardness and elastic modulus in the ranges of 28 to 33 GPa and 255 to 265 GPa, respectively, and the friction coefficient showed the lowest value of 0.24 on the multilayer coating with a bilayer period of 0.54 μm. The bilayer periods affected the adhesion strength of the multilayer coatings. From the scratch test, the critical load (Lc2) steadily increased with the decreasing of the bilayer period, and the CrZrN/CrZrSiN multilayer coating with a bilayer period of 0.45 μm showed the highest critical load (Lc2) of 79 N. In the case of the annealing test, the bilayer periods affected the thermal stability of the multilayer coatings, and the CrZrN/CrZrSiN multilayer coatings with 0.54 μm showed a maximum hardness value of approximately 30 GPa up to 800 °C.

Design architecture of colorful Si-DLC/PLC nanostructured multilayer films for robust superlubricity at high contact stress in dry N2 atmosphere

Diamond-like carbon (DLC) enables the design of novel lubricant structures to realize macroscale superlubricity in harsh working conditions. In this work, a series of nanostructured multilayer Si-DLC/PLC films with colorful appearances were developed to provide a lubrication state with near-zero friction and wear for responding the challenge of lubrication requirement in high-load operation environment. The results reveal the crucial role of structural parameter, namely the thickness of a bilayer period λ (i.e., 9–324 nm), in determining the construction architecture, mechanical properties and anti-friction lubricity of the multilayered films. Specifically, a bilayer period of 324 nm (total film thickness of 1.53 μm) endows the film with a superlow friction coefficient of 0.003 and a near-zero wear rate of 4.06 × 10−9 mm/Nm under a peak Hertz contact pressure of 1.76 GPa. The relationship between the load-bearing capacity, nano-clustering transformation of the sliding interface and the steady state of superlubricity is investigated in detail to clarify its high-stress adaption and robustness of the anti-friction features. The design architecture of well-tailored multicomponent and nanostructured multilayer films indeed offers an effective theoretical and technical solution to the long-term lubrication and protection of mechanical moving parts under heavy load conditions.