Nano-multilayer Films Research Articles

Properties of CrN/Mo2N nano-multilayer films synthesized by multi-cathodic arc ion plating system

CrN/Mo2N films were deposited by multi-cathodic arc ion plating on Si (100), 304 stainless steel and cemented carbide substrates with various bilayer periods (10–105nm). X-ray diffraction analysis revealed a face-centered-cubic structure of CrN and Mo2N sublayers. Rutherford backscattering spectrometry (RBS) was used to probe the elemental composition and their depth profiling. The multilayer structures exhibited characteristic oscillating RBS spectra. The nanohardness slightly increased at larger bilayer periods and the highest value of 29GPa was obtained at the bilayer period of 105nm. A correlation was realized among compressive residual stress, critical load, and nanohardness. The highest critical load Lc2 of 65–70N was found for the coatings on cemented carbide substrates with the minimal bilayer period of 12nm. The coefficients of friction and wear rates of the coatings were in the range of 0.29–0.35 and (6–8)×10−7mm3/N·m, respectively.

Thickness Effect On Nano-multilayered Sb/As2S3 Chalcogenide Thin Films

The nano multilayered thin films of Sb/As2S3 metal chalcogenide were prepared by thermal evaporation technique under high vacuum. The optical parameters such as optical band gap, tauc parameter, urbach energy were determined from the transmission spectra using Fourier Transform Infrared Spectroscopy. These properties are greatly influenced by the thickness of the nano layered Sb/As2S3 thin film. The Small Angle X-ray diffraction study reveals the amorphous nature of these films. The analysis reveals that the optical band gap decreases with increase in thickness due to Sb metal. The tauc parameter and urbach energy supports the optical property change. Such type of dependence is attributed to quantum size effect in semiconductors.

First-principles investigation on the electronic property and bonding configuration of NbC (111)/NbN (111) interface

The NbC (111)/NbN (111) interfaces were studied by first-principles calculation based on density functional theory to supply the theoretical basis for developing the novel NbC/NbN nano-multilayered film. Surface convergence calculations demonstrate that both NbC slab and NbN slab with more than thirteen atom-layers exhibit bulk-like interior feature. Thirty-six specific geometry models of NbC (111)/NbN(111) interface with different termination structures and stacking sequences were chosen. The calculated interfacial ideal work of adhesion and interfacial distance suggest that interface termination structure and stacking sequence both play the important role on influencing the interfacial stability, in which, C-terminated NbC is more inclined to join with the Nb-terminated NbN while the Nb-terminated NbC is more inclined to join with the N-terminated NbN. Moreover, for the C-N terminated and Nb-Nb terminated interfaces, the OT stacking sequence shows the highest stability, while for the C-Nb terminated and Nb-N terminated interfaces, the TL stacking sequence shows the highest stability. For the most stable C-Nb terminated and Nb-N terminated NbC (111)/NbN (111) interfaces, the atomic structure and the electronic transition from NbC to NbN are undertaken smoothly across interface. The chemical bond between the neighbor Nb atom and C or N atom in interface system shows both covalency and ionicity. Moreover, the transferred charge from Nb atom to N atom is larger than that from Nb atom to C atom, which may be the reason that Nb1-N terminated interface revealing the higher interfacial stability than C1-Nb terminated one.

Investigation of transport and magnetic properties of SiC/Cu diluted magnetic semiconductor nano-multilayer films

The SiC/Cu nano-multilayer films were deposited on Si substrates using radio frequency and direct current alternative sputtering technique. In this paper, the transport and magnetic properties of the films were investigated. XRR shows the SiC/Cu periodical structures of the films. XRD confirms that the 3C-SiC crystal structure is formed in the films without heating substrates. The XPS indicates that the Cu atoms substitute for Si sites of the SiC lattice and exist in a mixed valance state of Cu+ and Cu2+. The best fitting for the plots of ln ρ versus T−1/4 using the combination of the Mott and the band gap VRH models suggests that the carriers in the films are strongly localized. The films have a typical semiconductor characteristic and an obvious room temperature ferromagnetism which should arise from the bond magnetic polarons. The maximum values of saturation magnetization and carrier concentration are up to 15.2 emu/cm3 and 1.86E + 22/cm3 respectively.

Microstructure and superhardness effect of CrAlN/SiO2 nanomultilayered film synthesized by reactive magnetron sputtering

The CrAlN/SiO2 nanomultilayered films with different SiO2 layers thickness were synthesized by reactive magnetron sputtering. The effects of SiO2 layer thickness on the microstructure and mechanical properties of CrAlN/SiO2 nanomultilayered films were studied. The results reveal that, when SiO2 layer thickness is less than 0.7nm, originally amorphous SiO2 layers can be forced to crystallize under the “template effect” of NaCl-structured CrAlN layers and grow epitaxially with them, resulting in the preservation of columnar growth structure and remarkable superhardness effect with the maximum value of hardness of 38.9GPa. As the SiO2 layer thickness exceeds 0.7nm, however, SiO2 layers transform back into amorphous state, which destructs the epitaxial structure between CrAlN and SiO2 layers, leading to disappearance of columnar growth character and decrease of mechanical properties. The superhardness effect of CrAlN/SiO2 nanomultilayered film can be attributed to the joint effects of modulus-difference and alternating-stress strengthening mechanisms.

Fabrication and characterization of HfC/SiC nanomultilayered films with enhanced mechanical properties

A series of HfC/SiC nanomultilayered films with different SiC layer thickness were synthesized by reactive magnetron sputtering. The effect of SiC layer thickness on the microstructure and mechanical properties of HfC/SiC nanomultilayered films were studied. When SiC layer thickness was less than 0.9 nm, originally amorphous SiC layers were forced to crystallize and grow epitaxially with HfC layers, resulting in the improvement of crystallization integrality and enhancement in hardness and elastic modulus. The maximum hardness and elastic modulus could reach 36.2 GPa and 419 GPa, respectively. With further increase of SiC layer thickness, SiC layers changed back to amorphous state and damaged the epitaxial growth structure, leading to deterioration of mechanical properties.

Investigation of Ge2Sb2Te5/Si nano-multilayered films for phase-change memory applications

The phase-transition behavior and thermal stability of Ge2Sb2Te5/Si nano-multilayered films are investigated in this study. Our results reveal that the improvement in thermal stability and increase in the phase-transition temperature are not universal results for all nano-multilayered structures. The stress effect induced by thermal expansion during heating indeed could inhibit the crystallization of Ge2Sb2Te5/Si nano-multilayered films. The interface effect is believed to play a dominant role in thicker films, while the stress effect is active when the layer thickness is decreased. The gradual shift in the Raman peaks' position can support this scenario because they are modified by both the interface effect and the stress effect.

Effects of modulation period on microstructure, mechanical properties of TiBN/TiN nanomultilayered films deposited by multi arc ion plating

TiBN/TiN multilayered coating with different modulation periods (bilayer thickness) have been synthesized using typical cathodic arc plasma deposition equipment. The objective of this work is to study the influence of modulation period on the microstructure, mechanical and tribological properties. TiBN/TiN multilayer coatings exhibited a TiN (111), (200), (220) and TiB2 (220) crystallographic orientations and preferred TiN (111) orientation. With the decrease of modulation period from 12 nm to 1.9 nm, the mole ratio of B increased from 0.079 to 0.162 in addition to the average mole ratio of N was about 0.39 steadily, while the mole ratio of Ti decreased from 0.506 to 0.407. The microstructure of TiBN/TiN multilayered coating evolves form nanocrystalline TiN/a-BN to nanocomposite Ti(B,N) with an dense amorphous BN phase, The maximum values of hardness and elastic modulus reached 31.6 GPa and 336 GPa with a bilayer period of 1.9 nm and B:Ti ratio of 2:5.

遮熱技術：革新的次世代遮熱フィルムと省エネルギー評価技術の開発

An innovative heat shield film with high energy-saving performance is being developed under the TherMAT project. The new heat shield film with high visible transmittance and low solar heat gain is realized by using nano multi-layered films. Their performances have been improved by the optimization of polymer designing and the refining of the multi-layer laminating apparatus. The practical energy efficiency of the film was evaluated by AIST. AIST is developing new evaluation method of energy performance of heat shield films. The developed heat shield films in this project were installed to the testing facility in AIST. The cooling and heating loads of air conditioner and energy flow through windows were evaluated. These results show that the energy-saving level of the developed shading film is 10% higher than that of the commercialized product.

Experimental study on solid solution strengthening in nanocrystalline alloys using multilayered films

In nanocrystalline alloys, some microstructural factors are usually tied to grain interior composition, including grain size, grain boundary composition, and grain boundary width. Due to the coupling of these factors, it is challenging to reveal the individual effect of solid solution strengthening. In this paper, sputtered Cu–Ti alloy multilayered films were designed to isolate the effect of solid solution strengthening in nanocrystalline alloys. Two series of nano-multilayered films were synthesized consisting of different low-alloy-content crystalline layers (6–188nm thick) and same high-alloy-content amorphous layers (~5nm thick). The columnar crystals in crystalline layers with two different compositions both have the same diameters. The comparison of the two series of multilayered films show that the increase of Ti content from 0.3 to 5.3at% results in a constant hardness enhancement of 1.5±0.2GPa, as the height of columnar crystals in diameter of 10nm decreases from 188nm to 6nm. This indicates that the solid solution strengthening effect of nanocrystalline alloys is independent of grain size not only when the deformation behavior is dominated by intragranular dislocation mechanism as coarse-grained ones, but also, more importantly, when it becomes dominated by grain boundaries.

Effect of Si content on microstructural evolution and superhardness effect of TiN/CrAlSiN nanomultilayered films

Through introducing the CrAlSiN modulation layers consisted of CrAlN and SiNx phases, a series of TiN/CrAlSiN nanomultilayered films with different Si content were synthesized by reactive magnetron sputtering. The effect of Si content on microstructural evolution and superhardness effect of TiN/CrAlSiN nanomultilayered film was investigated by XRD, HRTEM and nanoindentation techniques. When inserted by CrAlSiN nano-layers with Si:CrAl ratio less than 4:21, TiN layers can force CrAlSiN layers to transform into fcc structure and grow epitaxially with them, leading to appearance of the superhardness effect. The columnar crystal structure of TiN/CrAlSiN nanomultilayered film can be effectively refined by insertion of the CrAlSiN layers due to thermodynamic incompatibility of CrAlN and SiNx. As the Si content further increases, the amount of amorphous SiNx phase increases, which makes the CrAlSiN layers present amorphous feature and blocks the epitaxial growth structure within the TiN/CrAlSiN nanomultilayered film, resulting in the decrease of hardness and elastic modulus.

High-Temperature Corrosion of Nano-Multilayered TiAISiN Thin Films in Ar-0.2%SO2 Gases.

Nano-multilayered TiAlSiN films with a composition of 26Ti-16.3Al-1.2Si-56.5N (at.%) were deposited onto steel via arc ion plating, and corroded at 800-900 °C for 30 h in Ar-0.2%SO2 gases. The films were corrosion resistant, because the oxidation process dominated sulfidation. The scales consisted primarily of Al2O3 and TiO2, where a small amount of Si dissolved.

Influence of heat treatment on characteristics of In2O3/Ag/MoO3 multilayer films as transparent anode for optoelectronic applications

In this study, In2O3/Ag/MoO3 (IAM) nano-multilayer films are designed, and optimum thickness of each layer is calculated. These films were deposited by thermal evaporation technique and then annealed in air atmosphere at different temperatures for 1 h. The effects of annealing temperature on electrical, optical, and structural properties of the IAM system were investigated. The UV–visible–near-IR transmittance and reflectance spectra confirmed that the annealing temperature has significant influence on the electro‐optical characteristics of IAM films. High-quality IAM films with a low sheet resistance of 8.2 (Ω/□) and the maximum optical transmittance of 85 % at 120 °C annealing temperature were obtained. The effect of heat treatment on surface roughness of the layers was also investigated. Figure-of-merit quantity showed that the IAM films annealed at 120 °C have the best performance. X-ray diffraction patterns showed that the crystallinity of the structures enhanced with increase in annealing temperature. Organic light-emitting diodes (OLEDs) were fabricated on IAM anodes. The current density–voltage–luminance (J–V–L) characteristic measurements show that the electroluminescence performances of OLED with IAM anode are improved compared with the conventional ITO-based device. The results indicate that the designed system is suitable for use as transparent conductive anode in optoelectronic devices.

Oxidation behavior of amorphous boron carbide–silicon carbide nano-multilayer thin films

This experiment studied the effect of nano-multilayer structures of boron carbide film with silicon carbide (SiC) layers on oxidation behavior and hardness. The multilayer films were deposited at 450°C using an unbalanced dual-gun magnetron sputtering system with stoichiometric B4C and SiC targets. The period of the multilayer system (the thickness of one pair of boron carbide and SiC layers) with a constant film thickness was varied between 2.3nm and 22.1nm. The structures of these multilayer thin films were amorphous irrespective of the period. A remarkable hardness enhancement, frequently observed in crystalline nano-multilayer thin film systems, did not appear. The maximum hardness of the multilayer thin film was measured to be about 36GPa, similar to that of the monolithic boron carbide film deposited under the same condition. Oxidation was, however, greatly reduced by the insertion of the SiC layers. Oxidation was rarely observed at temperatures up to 1200°C, the maximum experimental temperature, whereas significant oxidation was observed at around 700°C in the case of the boron carbide monolithic film.

The superhardness effect in TiC/B4C nanomultilayer film with interface reaction

Abstract A series of TiC/B 4 C films have been prepared by magnetron sputtering techniques. The interface reaction, microstructure and mechanical properties have been characterized by X-ray photoelectron spectroscopy, X-ray diffraction, high-resolution transmission electron microscopy and nanoindention device, and the effect of structure evolution on the mechanical properties has been studied. The results show the interface reaction between TiC and B 4 C can react into TiB 2 and C. When the deposited B 4 C layer thickness is less than 0.5 nm, the multilayer will transit into TiC x /TiB 2 type film in which TiC x and TiB 2 should grow coherently with each other, and the film attains the highest hardness of 40.1GPa. Further increasing the deposited B 4 C layer thickness,the hardness will drop down quickly for the disruption of coherent growth structure, and the film should form sandwich structure. Based on the results, several basic rules have been proposed to design this kind of multilayers.

Microstructure, mechanical and tribological properties of TiMoN/Si3N4 nano-multilayer films deposited by magnetron sputtering

TiMoN/Si3N4 nano-multilayer films with different Si3N4 layer thickness were synthesized using magnetron sputtering by changing the Si target current. The TiMoN/Si3N4 nano-multilayer films exhibited strong microstructure and properties dependence on the structures of Si3N4 layer. When Si3N4 layer thickness (lSi3N4) was smaller than 0.8nm, Si3N4 layers maintained crystallization state, the as-deposited TiMoN/SiNx films exhibited much higher hardness and comparable coefficient of friction (COF) than that of MoNx/SiNx films. With the further increase of lSi3N4, Si3N4 layer transformed to amorphous state, the hardness of TiMoN/Si3N4 films decreased gradually from 29.9 to 20.1GPa and COF increased from 0.55 to 0.72. It totally shows better tribological properties than TiAlSiN/Si3N4 nano-multilayer films as a result of incorporating molybdenum nitride.

Microstructure, mechanical and tribological properties of TiN/Mo2N nano-multilayer films deposited by magnetron sputtering

TiN/Mo2N nano-multilayer films with modulation period ranging from 3nm to 9.8nm were deposited by magnetron sputtering. TiN and Mo2N monolithic films were also deposited for comparison. It was found that the (200) preferred orientated TiN/Mo2N nano-multilayer films exhibited fcc structure similar to B1-NaCl and formed isostructural superlattice with well defined interfaces between TiN and Mo2N layers. The multilayer films with modulation periods λ=3nm and 5.7nm exhibited superhardness with a value of about 41GPa. Both the coefficient of friction and specific wear rate of multilayer films increased from 0.29 to 0.44 and 5.8×10−17m3/Nm to 1.3×10−16m3/Nm, respectively, with the increase of the modulation period. The TiN/Mo2N nano-multilayer films exhibited improved mechanical and tribological properties compared to TiN and Mo2N monolithic films.

Structural evolution of yttrium nanolayer inserted in FeNi/Y nanomultilayered film

The FeNi/Y nanomultilayered films with different Y layer thickness (tY) were synthesized by magnetron sputtering. The structural evolution of Y nanolayer with increase in tY was investigated. When tY was less than 2nm, Y layers transformed to fcc structure under the template effect of FeNi layers and grew epitaxially with FeNi. With tY of 3nm, Y layers could not maintain the epitaxial growth, but present a transient amorphous state. As tY further increases to 4nm, Y layers transformed into the stable hcp structure. The microstructural evolution sequence of Y layers was fcc→amorphous→hcp structure, which could be explained by a thermodynamic model.

Martensitic transformation of FeNi nanofilm induced by interfacial stress generated in FeNi/V nanomultilayered structure.

FeNi/V nanomultilayered films with different V layer thicknesses were synthesized by magnetron sputtering. By adjusting the thickness of the V layer, different interfacial compressive stress were imposed on FeNi layers and the effect of interfacial stress on martensitic transformation of the FeNi film was investigated. Without insertion of V layers, the FeNi film exhibits a face-centered cubic (fcc) structure. With the thickness of V inserted layers up to 1.5 nm, under the coherent growth structure in FeNi/V nanomultilayered films, FeNi layers bear interfacial compressive stress due to the larger lattice parameter relative to V, which induces the martensitic transformation of the FeNi film. As the V layer thickness increases to 2.0 nm, V layers cannot keep the coherent growth structure with FeNi layers, leading to the disappearance of interfacial compressive stress and termination of the martensitic transformation in the FeNi film. The interfacial compressive stress-induced martensitic transformation of the FeNi nanofilm is verified through experiment. The method of imposing and modulating the interfacial stress through the epitaxial growth structure in the nanomultilayered films should be noticed and utilized.

Magnetic reversal mechanism in strong perpendicular magnetic anisotropic CoPt/AlN multilayer film

Magnetic reversal mechanism of the Sub/AlN5nm/[CoPt2nm/AlN5nm]5 nano multilayer film, which shows strong perpendicular magnetic anisotropy (Ku=6.7×106erg/cm3), has been studied. The angle-dependent magnetic hysteresis loops of this highly perpendicular anisotropic CoPt/AlN multilayer film were measured in the present work, applying a magnetic field along different angles φ with respect to the film normal. It demonstrates that the magnetic reversal of the CoPt ultrathin layers in the CoPt/AlN multilayer film is occurred by the reversible magnetization rotation and the irreversible displacement of domain walls. The φ-dependent part of coercive field is resulted from the internal stress according to the Kondorsky and Kersten model. The φ-independent part of coercive field implies some random and isotropy pinning centers (e.g., vacancies, dislocations, grain boundaries) in the ultrathin CoPt layers. Our work is useful for coercivity control of metal/ceramics layered structures, in particular the perpendicular magnetic tunneling junctions.