Evaluation of antimicrobial abilities of Cr2N/Cu multilayered thin films

Nine kinds of nanostructured Cr₂N/Cu multilayer thin films were deposited by the bipolar asymmetry reactive pulsed DC magnetron sputtering system. The antibacterial tests of coatings with various bilayer periods (Λ) and different Cr₂N/Cu thickness ratios were performed to evaluate the bactericidal ability by E. coli, S. aureus and P. aeruginosa, respectively. The Λ value, thickness values of Cr₂N to Cu layers significantly affected the bactericidal rates. The 100% bactericidal rates were achieved when the Λ value reached 20 nm. For the same Λ = 12 nm Cr₂N/Cu multilayered coatings, the thickness ratio of Cr₂N to Cu also showed strong influence on the bactericidal rates.     

Tribological behavior of CrAlSiN/W2N multilayer coatings deposited by DC magnetron sputtering

The CrAlSiN/W₂N multilayer coatings were fabricated by DC magnetron sputtering. The bilayer periods of multilayer films were controlled in the range from 3 to 20 nm. The cross-sectional structure of multilayer and monolayer coatings was evaluated by transmission electron microscopy (TEM). The wear behavior of monolayer and multilayer coatings was investigated by a pin-on-disc tribometer. The nano-scratch tester was employed to study the crack propagation of scratched coatings. The images of wear scars were observed by optical microscopy (OM). The cross-sectional image of scratched films was analyzed by transmission electron microscopy (TEM). Owing to the nano-layered structure and higher hardness (or H/E ratio), the multilayer coatings exhibited better wear resistance than homogeneous films. The coefficient of friction of CrAlSiN/W₂N multilayer coating with a bilayer period of 8 nm was around 0.6, and that of CrAlSiN homogeneous film was about 0.8. Different crack propagation mechanisms of CrAlSiN/W₂N multilayer and CrAlSiN monolayer coatings were proposed and discussed.     

Tribological and mechanical behaviors of TiN/CNx multilayer films deposited by magnetron sputtering

TiN/CN_x multilayer films with bilayer periods of 4.5-40.3 nm were deposited by direct-current magnetron sputtering. Layer morphology and structure of the multilayered films were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. The TiN/CN_x multilayers exhibited coherent epitaxial growth due to the mutual growth-promoting effect at small bilayer period and some crystalline regions going through the interface of TiN/CN_x. Nanoindentation tests showed that the hardness of the multilayers varied from 12.5 to 31 GPa, with the highest hardness being obtained with a bilayer period of 4.5 nm. The tribological properties of the films were investigated using a ball-on-disk tribometer in humid air, and the TiN/CN_x multilayer with a bilayer period of 4.5 nm also exhibited the lowest friction coefficient and the highest wear resistance.     

Structure and properties of Zr/ZrCN coatings deposited by cathodic arc method

Zr/ZrCN multilayers, with bilayer periods ranging from 4.4 to 70 nm, were deposited on C45 and M2 steels and Si substrates by the cathodic arc technique, in a CH₄ + N₂ atmosphere. The elemental and phase composition, modulation periodicity, texture, surface morphology, residual stress, hardness, adhesion, friction and wear behavior were investigated as a function of bilayer period and C/N ratio using AES, RBS, XRR, XRD and AFM techniques, surface profilometry, Vickers microhardness and scratch adhesion measurements, and tribological tests. Two types of Zr/ZrCN multilayers, with high and low C/(C + N) ratios (0.7 and 0.2, respectively) in the ZrCN sub-layer composition, have been prepared. The investigations indicated that the microchemical, microstructural, mechanical and tribological characteristics of the multilayered coatings depended on C/N ratio and bilayer period. For the optimum structure parameters (bilayer periods in the range 6–13 nm), the tribological performance of the multilayers was found to be superior to that of the ZrCN monolayers.     

Influence of multi-interfacial structure on mechanical and tribological properties of TiSiN/Ag multilayer coatings

The TiSiN/Ag multilayer coatings with bilayer periods of ~50, 65, 80, 115, 150, and 410 nm have been deposited on Ti6Al4 V alloy by arc ion plating. In order to improve the adhesion of the TiSiN/Ag multilayer coatings, TiN buffer layer was first deposited on titanium alloy. The multi-interfacial TiSiN/Ag layers possess alternating TiSiN and Ag layers. The TiSiN layers display a typical nanocrystalline/amorphous microstructure, with nanocrystalline TiN and amorphous Si₃N₄. TiN nanocrystallites embed in amorphous Si₃N₄ matrix exhibiting a fine-grained crystalline structure. The Ag layers exhibit ductile nanocrystalline metallic silver. The coatings appear to be a strong TiN (200)-preferred orientation for fiber texture growth. Moreover, the grain size of TiN decreases with the decrease of the bilayer periods. Evidence concluded from transmission electron microscopy revealed that multi-interfacial structures effectively limit continuous growth of single (200)-preferred orientation coarse columnar TiN crystals. The hardness of the coatings increases with the decreasing bilayer periods. Multi-interface can act as a lubricant, effectively hinder the cracks propagation and prevent aggressive seawater from permeating to substrate through the micro-pores to some extent, reducing the friction coefficient and wear rates. It was found that the TiSiN/Ag multilayer coating with a bilayer period of 50 nm shows an excellent wear resistance due to the fine grain size, high hardness, and silver-lubricated transfer films formed during wear tests.     

Schichten in der Kunststoffverarbeitung. Mittels MSPVD abgeschiedene CrxN-Schichten eröffnen neue Möglichkeiten für den Verschleißschutz von Plastifiziereinheiten

Coatings in polymer processing Cr_xN coatings produced by PVD-magnetron sputtering (MSPVD) open units For several years hard coatings have been used in plastic processing. The reduction of adhesion and contamination effects play a more and more important role besides the wear protection of injection moulds and extrusion tools. Applications of hard coatings in the field of highly stressed screws and barrels of plastification units are very seldom. In these cases the tribological effects are very intense so that the demanded wear resistance of hard coatings in the range 10μm is not sufficient. Different hard coatings based on titanium and chromium were tested according to their applicability for wear protection of screws in plastification units. Thickness, hardness, internal stresses and adhesion of the coatings were studied. Afterwards tribological tests in a model testing unit were investigated. Here the coatings were studied under tribological conditions, similar to those in a real plastification unit. The Cr_xN multilayer coatings showed extremely better wear resistance than the titanium based coatings. For this reason the Cr_xN coatings were optimized by help of the deposition parameters. These optimized coatings have been investigated according to their applicability for different polymers in comparison to other coating systems. First tests of CrCN/TiCN coated screw elements in practice showed very pleasing results. The test in practice with the optimized Cr_xN multilayer coating has yet to take place, but in the model tests the Cr_xN coatings showed excellent results.     

Modulation periods and ratios induced changes of microstructure and mechanical properties of AlN/ZrB2 multilayered coatings

AlN/ZrB₂ multilayered coatings were synthesized in a magnetron sputtering system. The extensive measurements were employed to investigate the influence of different nanoscale modulation periods and modulation ratios on microstructure and mechanical properties of the coatings. Analysis of X-ray diffraction, profiler and nanoindention indicated that multilayered coatings possessed much higher hardness and elastic modulus than monolithic AlN and ZrB₂ coatings. At the substrate negative bias of −80 V, maximum hardness (34.1 GPa) and elastic modulus (469.8 GPa) were obtained in the multilayer with Λ = 30 nm and t_AlN:t_ZrB2 = 1:3. This hardest multilayer showed a marked polycrystalline structure with the strong mixture of ZrB₂ (001), ZrB₂ (100), ZrB₂ (101), AlN (100) textures.     

The As-prepared surfaces of C-axis-oriented Nd1Ba2Cu3Oy thin films characterized using scanning probe microscopes

Recently, superconducting Nd₁Ba₂Cu₃O_y (Ndl23) thin films with high superconducting transition temperature (T _c) have been successfully fabricated at our institute employing the standard laser ablation method. In this paper, we report the results of surface characterization of the Nd123 thin films using an ultrahigh vacuum scanning tunneling microscope/spectroscopy (UHV-STM/STS) and an atomic force microscope (AFM) system operated in air. Clear spiral pattern is observed on the surfaces of Nd123 thin films by STM and AFM, suggesting that films are formed by two-dimensional island growth mode. Contour plots of the spirals show that the step heights of the spirals are not always the integer or half-integer number of thec-axis parameter of the structure. This implies that the surface natural termination layer of the films may not be unique. This result is supported byI-V STS measurements. The surface morphology of the Nd123 thin films is compared with that of thec-axis-oriented Y₁Ba₂Cu₃S_y thin films. Surface atomic images of the as-prepared Nd123 thin films are obtained employing both STM and AFM. STS measurements show that most of the surfaces are semiconductive. The results of STS measurements together with the fact that we are able to see the surface atomic images using scanning probe microscopes suggest that exposure to air does not cause serious degradation to the as-prepared surfaces of Nd123 thin films.     

Effect of annealing on characteristics of Ni48Fe12Cr40/Ni80Fe20 bilayer films deposited on Si(1 0 0)/SiO2 by electron beam evaporation

Ni₄₈Fe₁₂Cr₄₀(7 nm)/Ni₈₀Fe₂₀(40 nm) bilayer films and Ni₈₀Fe₂₀(40 nm) monolayer films were deposited at ambient temperature on Si(1 0 0)/SiO₂ substrates by electron beam evaporation. The effect of annealing on the structure, composition, magnetization and magnetoresistance of the Ni₄₈Fe₁₂Cr₄₀/Ni₈₀Fe₂₀ bilayer films was investigated. The structure of the Ni₄₈Fe₁₂Cr₄₀/Ni₈₀Fe₂₀ bilayer films remains stable for annealing temperature up to 280 °C. For the as-deposited bilayer film the introducing of the Ni₄₈Fe₁₂Cr₄₀ underlayer promotes both the [1 1 1] texture and grain growth in the Ni₈₀Fe₂₀ layer. The annealing promotes the grain growth of the Ni₄₈Fe₁₂Cr₄₀/Ni₈₀Fe₂₀ bilayer films when the annealing temperature exceeds 280 °C. After annealing at a temperature over 280 °C, Cr atoms inside the Ni₄₈Fe₁₂Cr₄₀ layer diffuse into the Ni₈₀Fe₂₀ layer and segregate on the surface of the Ni₈₀Fe₂₀ layer. The Ni₄₈Fe₁₂Cr₄₀ underlayer as a seed layer can enhance the anisotropic magnetoresistance ratio of the Ni₈₀Fe₂₀ layer at a annealing temperature up to 280 °C compared with Ni₈₀Fe₂₀ monolayer film. After annealing at a temperature over 280 °C, however, the anisotropic magnetoresistance ratio of the Ni₈₀Fe₂₀ monolayer films exceeds that of the Ni₄₈Fe₁₂Cr₄₀/Ni₈₀Fe₂₀ bilayer films. For all annealing temperatures, the coercivities of the Ni₄₈Fe₁₂Cr₄₀/Ni₈₀Fe₂₀ bilayer films are smaller than those of the Ni₈₀Fe₂₀ monolayer films.     

Highly reflective nc-Si:H/a-CNx:H multilayer films prepared by r.f. PECVD technique

Multilayer thin films consisting of a-CN_x:H/nc-Si:H layers prepared by radio-frequency plasma enhanced chemical vapour (r.f. PECVD) deposition technique were studied. High optical reflectivity at a specific wavelength is one of major concern for its application. By using this technique, a-CN_x:H/nc-Si:H multilayered thin films (3-11 periods) were deposited on substrates of p-type (111) crystal silicon and quartz. These films were characterized using ultra-violet-visible-near infrared (UV-Vis-NIR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, field effect scanning electron microscopy (FESEM) and AUGER electron spectroscopy (AES). The multilayered films show high reflectivity and wide stop band width at a wavelength of approximately 650 ± 60 nm. The FTIR spectrum of this multilayered structure showed the formation of Si-H and Si-H₂ bonds in the nc-Si:H layer and CC and N-H bonds in a-CN_x:H layer. SEM image and AES reveal distinct formation of a-CN_x:H and nc-Si:H layers in the cross section image with a decrease in interlayer cross contamination with increasing number of periods.     

Fabrication and performance of TiN/TiAlN nanometer modulated coatings

TiN/TiAlN multilayered coatings with bilayer periods (λ_BD) ranging from 6 to 30 nm were prepared on TC4 alloy and Si (100) wafer substrates by magnetic filtered pulsed vacuum cathodic arc plasma technique. The analyses with scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray energy dispersive spectroscope (EDS) and X-ray photoelectron spectroscope (XPS) with Ar + sputtering indicated that the as-deposited coatings had nanometer modulated structure, TiN and TiAlN with (111) preferred orientation were the main compounds and the average atoms ratio of N:(Ti + Al) was about 1.24-1.29. Scratch test showed that the coatings were fairly adherent to TC4 substrates, and the maximal critical load was about 57 N. The highest nano-hardness and modulus about 28 GPa and 283 GPa, respectively, were obtained for the multilayer with λ_BD = 12 nm, examined with nano-indentation method. The electrochemical corrosion test showed that the coatings improved the TC4 alloy's property of anti-corrosion effectively, especially with λ_BD = 20 nm.     

Annealing effects on microstructure and mechanical properties of sputtered multilayer Cr(1 − x)AlxN films

Multilayer Cr_(1 − x)Al_xN films with a total thickness of 2 μm were deposited on high-speed steel by medium frequency magnetron sputtering from Cr and Al-Cr (70 at.% Al) targets. The samples were annealed in air at 400 °C, 600 °C, 800 °C and 1000 °C for 1 hour. Films were characterized by cross-sectional scanning electron microscopy and X-ray diffraction analysis. The grain size of the as-deposited multilayer films is about 10 nm, increasing with the annealing temperature up to 100 nm. Interfacial reactions have clearly changed at elevated annealing temperatures. As-deposited films' hardness measured by nanoindentation is 22.6 GPa, which increases to 26.7 GPa when the annealing temperature goes up to 400 and 600 °C, but hardness decreases to 21.2 GPa with further annealing temperature increase from 600 to 1000 °C. The multilayer film adhesion was measured by means of the scratch test combined with acoustic emission for detecting the fracture load. The critical normal load decreased from 49.7 N for the as-deposited films to 21.2 N for the films annealed at 1000 °C.     

Exchange-coupled Fe3O4/L10-FePt bilayer films by controlled oxidation of Fe/Pt multilayer

A Fe₃O₄/L1₀-FePt bilayer thin-film magnet was fabricated via a simple one-step process by annealing Fe/Pt multilayer thin films in a N₂ gas flow. X-ray diffraction and plane-view selected-area electron diffraction results are identified with magnetite phase (Fe₃O₄) and L1₀-FePt. Cross-sectional transmission electron microscopy images show the two phases form a bilayer structure. Magnetic hysteresis loops of the bilayer show single phase behavior which is interpreted as a result of the soft Fe₃O₄ phase exchange-coupled with the hard L1₀-FePt phase, consistent with micromagnetic simulation prediction. Such bilayer structure may have potential for coercivity control in high density magnetic recording application.     

Microstructure,Interface, and Properties of Multilayered CrN/Cr_2O_3 Coatings Prepared by Arc Ion Plating

There has been much interest in developing multilayered or nanolayered physical vapor deposition（PVD） coatings identified as a group of promising protective coatings for their excellent mechanical properties and corrosion resistance. In this study, the multilayered Cr N/Cr2O3 coatings with different bilayer periods（L） were synthesized on the polished high speed steel substrates from a Cr target with the alternative atmosphere of pure nitrogen and pure oxygen by arc ion plating（AIP） technique. The results revealed that the microstructure,morphologies and properties of the multilayered coatings were strongly influenced by the bilayer period（L）.There were two kinds of interfaces in the multilayered Cr N/Cr2O3coatings： the sharp ones and the blurry ones. With reducing the value of L, the macro-particles densities decreased gradually, whereas the coating microhardness, adhesive strength and wear resistance first increased, and then decreased slightly or remained stable as the bilayer period L 〈 590 nm. The multilayered Cr N/Cr2O3 coating with the bilayer period L of 590 nm possessed the best comprehensive properties, namely the highest microhardness, the strongest adhesion, and the lowest wear rate.     

Low cost CuInSe2 thin films production by stacked elemental layers process for large area fabrication of solar cell application

Low cost deposition of large area CuInSe₂ (CIS) thin films have been grown on Mo-coated glass substrate by simple and economic stacked elemental layer deposition technique in vacuum. The grown parameters such as concentration of Cu, In and Se elements have been optimized to achieve uniform thin film in vacuum chamber. The as-grown Cu/In/Se stacked layers have been annealed at 200 °C and 350 °C for 1 h in air ambient. The as-grown and annealed films have been further subjected to characterization by X-ray diffraction (XRD), optical absorption, atomic force microscopy (AFM) and I-V measurement techniques. XRD patterns revealed that as-grown Cu/In/Se stacked layers represent amorphous nature while annealed CIS film reproduces nano-polycrystalline nature with chalcopyrite structure. The optical band gap of annealed films increases with respect to air annealing which confirms the reduction of crystallite size. Surface morphology of as-grown Cu/In/Se stacked layers and annealed CIS thin films have been confirmed by AFM images. The electrical measurements show enhancement of conductivity which is useful for solar cell application.     

ZnO/Cu/ZnO multilayer films: Structure optimization and investigation on photoelectric properties

A series of ZnO/Cu/ZnO multilayer films has been fabricated from zinc and copper metallic targets by simultaneous RF and DC magnetron sputtering. Numerical simulation of the optical properties of the multilayer films has been carried out in order to guide the experimental work. The influences of the ZnO and Cu layer thicknesses, and of O₂/Ar ratio on the photoelectric and structural properties of the films were investigated. The optical and electrical properties of the multilayers were studied by optical spectrometry and four point probe measurements, respectively. The structural properties were investigated using X-ray diffraction. The performance of the multilayers as transparent conducting coatings was compared using a figure of merit. In experiments, the thickness of the ZnO layers was varied between 4 and 70 nm and those of Cu were between 8 and 37 nm. The O₂/Ar ratios range from 1:5 to 2:1. Low sheet resistance and high transmittance were obtained when the film was prepared using an O₂/Ar ratio of 1:4 and a thickness of ZnO (60 nm)/Cu (15 nm)/ZnO (60 nm).     

Influence of Ar/N2 Flow Rate on Structure and Property for TaN/NbN Multilayered Coatings

TaN/NbN multilayered coatings with nanoscale bilayer periods were synthesized at different Ar/N2 flow rates by RF （radio frequency） magnetron sputtering. XRD （X-ray diffraction） and Nano Indenter System were employed to investigate the influence of Ar/N2 flow rate （FAr：FN2） on microstructure and mechanical properties of the coatings. The low-angle XRD pattern indicated a well-defined composition modulation and layer structure of the multilayered coating. All multilayered coatings almost revealed higher hardness than the rule-of-mixtures value of monolithic TaN and NbN coatings. At FAr：FN2=10, the multilayered coating possessed desirable hardness, elastic modulus, internal stress, and fracture resistance, compared with ones synthesized at other Ar/N2 flow rates. The layered structure with strong mixture of TaN （110）, （111）, （200） and Nb2N （101）textures should be related to the enhanced mechanical properties.     

Microstructure characterization of multilayered TiSiN/CrN thin films

Monolayered TiSiN and multilayered TiSiN/CrN coatings were synthesized by a cathodic arc deposition process. The chromium and Ti/Si (80/20 at.%) alloy targets were adopted as the cathode materials, altering the ratio of cathode current (I[TiSi]/I[Cr]) to obtain various multilayer periodic thicknesses of multilayered TiSiN/CrN coatings. X-ray diffraction and TEM analyses showed that all the deposited monolayered TiSiN and multilayered TiSiN/CrN films possessed the B1-NaCl structure. In this study, it was shown that the multilayer periods (Lambda) of the TiSiN/CrN deposited at I[TiSi]/I[Cr] cathode current ratios of 1.8, 1.0, and 0.55 were 8.3 nm, 6.2 nm, and 4.2 nm, respectively, with multilayer periodic thicknesses decreasing with smaller I[TiSi]/I[Cr] cathode current ratios. An amorphous phase was found at the boundaries of the TiN/CrN column grains. In addition, the multilayered TiSiN/CrN coatings displayed a lamellar structure that was well-defined and nonplanar between each TiN and CrN layer.     

Nanoscale Multilayered ZrAlN/ZrB2 Coatings Synthesized by Magnetron Sputtering

Multilayered ZrAlN/ZrB2 coatings containing alternating bilayer periods were synthesized by dc magnetron sputtering technique. The intensities of ZrN （111） or ZrN （200） textures in the structure of the nanolayers depended on the bilayer period as well as N2 gas partial pressure during deposition. Nanoindentation testing showed that hardness and internal stress of the nanolayers varied with the bilayer period and crystallographic orientation in the coatings. The hardness of the nanolayers with bilayer periods of 3-6 nm was enhanced （-27%） over the rule-of-mixture value. A low percent of N2 in processing gas was proved to be benefitial to the synthesis of high hard nanoscale multilayered coatings.     

The electromagnetic interference shielding effect of indium-zinc oxide/silver alloy multilayered thin films

A study was made to examine the electromagnetic interference (EMI) shielding effect of multilayered thin films in which indium-zinc oxide (IZO) thin films and Ag or Ag alloy thin films were deposited alternately at room temperature using a RF magnetron sputtering. The optical, electrical and morphological properties of the constituent layers were analyzed using an ultraviolet-visible photospectrometer, a 4-point probe and an atomic force microscopy (AFM), respectively. The EMI shielding effect of the multilayered thin films was also measured using a coaxial transmission line method. A detailed analysis showed that the control of the film morphologies, i.e., the surface roughnesses of the constituent metal layers was essential to an accurate estimate of the electrical and optical properties of multilayered coatings. It was shown that properly designed IZO/Ag alloy multilayered thin films could yield a visible transmission of more than 70%, a sheet resistance of less than 1 Ω/sq., together with an EMI shielding effect larger than 45 dB in the range from 30 to 1000 MHz.