Multilayer Film Structures Research Articles

Fano resonance based on ENZ mode in multilayer film and its optical switch application

This paper proposes a multilayer film structure consisting of an Au film, a Dysprosium-doped cadmium oxide (CdO:Dy) layer, and a SiO2 dielectric layer. The epsilon-near-zero (ENZ) mode is indirectly excited by the surface plasmon polariton (SPP) mode, and Fano resonance can be excited by the coupling of the two modes. The higher the wavelength-sensitivity of the real part of the dielectric constant of the ENZ material at the ENZ wavelength, the narrower the bandwidth of Fano resonance in the reflection spectrum. The indium tin oxide (ITO) is used to replace CdO:Dy as a switching material, and the ENZ wavelength is dynamically controlled by bias voltage. The ON and OFF states of the reflection spectrum can be switched at the wavelength of 1410 nm, achieving an insertion loss of 0.56 dB, an extinction ratio of 13.44 dB, and a figure of merit of 23.48 at this wavelength. This multilayer film structure has potential applications in the field of optical switches.

The problem of protecting a person from the effects of low-frequency electromagnetic fields in modern society. Possible ways to solve it

The paper considers the problem of the impact of low-frequency electromagnetic fields (EMF) generated by electric vehicles (EV) and household appliances on humans in modern society. The data on the effect of EMF on human health and regulatory documents establishing requirements for electromagnetic safety are presented. The method of electromagnetic shielding and materials for the implementation of this method are considered as a promising method for solving the problem. The levels of electromagnetic radiation from a number of EV and household electrical appliances have been experimentally measured. The efficiency of electromagnetic shielding of materials based on single-layer coatings of Ni80Fe20 alloys, multilayer film structures Ni80Fe20/Cu and amorphous metal alloys AMAG172 has been estimated using a computational method. It is shown that electromagnetic screens based on these materials significantly reduce the levels of exposure to EMF of EV and household electrical appliances on humans, which allows us to approach the hygienic standards recommended by doctors and meet the requirements of regulatory documents on remote control.

Memristor Effect in Layered Film Structures

Equivalent electrical circuits of multilayer film structures with memristor switching of resistance at interlayer boundaries and at the boundaries of crystal grains in each layer are proposed. Numerical modeling of the current-voltage characteristics of such structures has shown that their loop-shaped form, typical of memristors, is transformed into a linear ohmic dependence of the total current on the magnitude of the applied external voltage as both the number of layers and the number of grains in each layer increase. A certain combination of the number of layers and grains in a layer has been established, at which the maximum total current flowing through the structure and the ratio of resistances in the “off” and “on” states reach the highest values.

Ultrasmooth Ti/Al multilayer with a Ti seed layer for EUV applications

Al-base multilayers have attracted much interest in the extreme ultraviolet (EUV) optics field, but high roughness of this multilayer due to the Al film is still a big concern. Here, a strategy of the seed layer was proposed to reduce the surface roughness and intermixing layer thickness of the Al-base multilayer. Ti film is not only a seed layer, but also an absorption layer in this novel multilayer. An optimized Ti/Al multilayer film structure was designed to work at 21.1 nm, while investigating the use of Ti as a seed layer to reduce the roughness and enhance the peak reflectivity. The experimental results showed that the Ti seed layer effectively reduced the surface roughness and intermixing layer thickness and improved the reflectance. At 21.1 nm, the peak reflectance reached 39.6%, with a bandwidth of only 1.0 nm and an RMS roughness of 0.17 nm. Ti/Al multilayer also exhibits good stability. This multilayer has potential application in high-precision optics, such as corona detection, which requires extreme low light scattering of multilayer mirror.

A new method for characterizing the atomic composition distribution and interface structure of ultrathin multilayer films using molecular dynamics simulation assisted ARXPS

Characterizing ultrathin multilayer films' atom distribution and interface structure remains challenging. This paper innovatively characterized the chemical composition and distribution of Pt/Co/W ultrathin multilayer films by ARXPS. Molecular dynamics simulated the growth process of films to correspond to that in experiment. The results show that through ARXPS, the actual structure of Pt (2 nm)/Co (t = 0.5–3 nm)/W (2 nm) film could be obtained. For Pt (2 nm)/Co (2 nm)/W (2 nm) film, the actual structure was Pt/Co (1.73 nm)/W (0.78 nm)/WO3 + WO2 (1.48 nm). W at the top layer significantly diffused to the bottom layers, and oxidized W reduced from the surface to the interior of multilayer films. Molecular dynamics simulation confirmed that the interdiffusion degree of Co and W atoms was improved with the increase of Co atoms. The growth modes of Co and W layers were respectively layer-by-layer and island. As the number of Co atoms increased, the relative surface roughness of Co and W layers and the relative interface roughness of Co/W were increased. The in-plane magnetic anisotropy and coercivity were respectively enhanced and decreased due to the change in the surface/interface structure. This paper provides a new idea for analyzing ultrathin multilayer films' atom distribution and interface structure.

Intelligent Space Thermal Control Radiator Based on Phase Change Material with Partial Visible Transparency

Coating structures with dynamically adjustable infrared emissivity are crucial in spacecraft components to cope with the transient thermal environments of space. For a long time, thermochromic phase change materials have been widely used in applications requiring emissivity adjustment, and optimizing the range of adjustable infrared emissivity has always been at the forefront of research. However, reducing the absorption of solar radiation has significant implications for the practical application and thermal stability of spacecraft components in space environments. In this paper, we propose a multilayer film structure based on the phase change material VO2 combined with the materials ZnSe and ITO to achieve low solar radiation absorption and adjustable infrared emissivity for intelligent thermal radiators in space. Through finite element simulation analysis of the structure, we achieve a solar radiation absorption rate of 0.3 and an adjustable infrared emissivity of 0.49. According to Stefan–Boltzmann’s law, the structure exhibits strong radiative heat dissipation at high temperatures and weak energy dissipation at low temperatures to maintain the thermal stability of the device and ensure efficient operation. The intelligent thermal radiator operates based on the principles of Fabry–Perot resonance. Therefore, the multilayer structure based on the phase change material VO2 demonstrates excellent performance in both solar radiation absorption and adjustable infrared emissivity, showcasing its tremendous potential in the field of intelligent thermal control in aerospace.

Multispectral stealth multilayer etched film structure based on ultrathin silver.

Spontaneous infrared radiation dissipation is a critical factor in facilitating object cooling, which influences the thermal stability and stealth efficacy of infrared stealth devices. Furthermore, the compatibility between efficient visible, infrared, and radar stealth is challenging due to different camouflage principles in different bands. This Letter presents a five-layer etched film structure to achieve multispectral stealth, and the utilization of the high-quality ultrathin silver films enables highly efficient infrared selective emission. This etched film structure with few layers demonstrates potential applications in diverse domains, including multi-band anti-detection and multispectral manipulation.

Multifield-Modulated Spintronic Terahertz Emitter Based on a Vanadium Dioxide Phase Transition.

The efficient generation and active modulation of terahertz (THz) waves are strongly required for the development of various THz applications such as THz imaging/spectroscopy and THz communication. In addition, due to the increasing degree of integration for the THz optoelectronic devices, miniaturizing the complex THz system into a compact unit is also important and necessary. Today, integrating the THz source with the modulator to develop a powerful, easy-to-adjust, and scalable or on-chip THz emitter is still a challenge. As a new type of THz emitter, a spintronic THz emitter has attracted a great deal of attention due to its advantages of high efficiency, ultrawide band, low cost, and easy integration. In this study, we have proposed a multifield-modulated spintronic THz emitter based on the VO2/Ni/Pt multilayer film structure with a wide band region of 0-3 THz. Because of the pronounced phase transition of the integrated VO2 layer, the fabricated THz emitter can be efficiently modulated via thermal or electric stimuli with a modulation depth of about one order of magnitude; the modulation depths under thermal stimulation and electrical stimulation were 91.8% and 97.3%, respectively. It is believed that this multifield modulated spintronic THz emitter will provide various possibilities for the integration of next-generation on-chip THz sources and THz modulators.

Application of Multilayered Blend Films as Soft, Stretchable, Self‐Adhesive, and Self‐Healing Absorption‐Dominant EMI Shielding and Microwave Absorber

AbstractSolution‐processable organic conductor–supramolecular elastomer blends are emerging materials for intrinsically stretchable and autonomously self‐healing organic electronics. Herein, the feasibility of a heterogenous multiphase polymer blend is demonstrated for soft, ultraflexible, self‐adhesive, and self‐healing multilayered film structures for electromagnetic interference (EMI) shielding and microwave absorber (MWA) purposes. The developed soft multilayered films achieve a 5–40 fold improvement in the thickness of the MWA compared to the current state‐of‐the‐art. The thickness normalized reflection loss (RL) is up to 65.26 dB mm−1 with 8.5 GHz bandwidth at 18–26.5 GHz. The maximum thickness normalized EMI shielding effectiveness peaks at up to 175 dB mm−1. The EMI shielding and MWA properties are maintainable up to 150% tensile strain with only a small decrease in the overall attenuation and RL. Furthermore, the developed films are capable of fully autonomously self‐healing and achieve a tough adhesion in temperatures of −30–145 °C, and underwater with maximum single‐lap shear adhesion strength of ≈481.5 kPa to soft thermoplastic polyurethane films. Thus, the developed multilayered films can be utilized for absorption‐dominant EMI shielding or MWA purposes as stretchable coatings. The developed materials also show considerable potential for emerging damage and puncture‐resistant organic soft electronics with autonomous material‐level self‐healing.

Customized designs, preparations, and characterizations of high-performance multilayer VO2-based thermochromic smart coatings

VO2-based thermochromic coatings have gained much attention in temperature-adaptive smart windows, and constructing multilayer film structures is the main way to obtain high thermochromic performances. Based on the self-developed objective-orientated automatic optimization code, the present research realized customized designs of thermochromic multilayer coatings composed of VO2, TiO2, and SiO2 from the objectives of visible luminance (Tlum) and solar light modulation (ΔTsol). The TiO2/VO2/s, VO2/TiO2/s, TiO2/VO2/TiO2/s, and SiO2/TiO2/VO2/TiO2/s (s denotes substrate) multilayer film systems were then prepared by magnetron sputtering and vacuum controllable heating, with their structures, insulator-metallic transition, and thermochromic properties being carefully studied. The result showed that the best trade-off between high Tlum and high ΔTsol was achieved for these film assemblies, and solar light modulation was mainly limited at the near-IR wavelength region of the solar spectrum, with the difference between cool- and hot-state Tlum being greatly reduced. In the case of the four-layer SiO2/TiO2/VO2/TiO2/s, very high average Tlum (60%) and high ΔTsol (14%) were obtained. A 100 × 100 mm2 of the SiO2/TiO2/VO2/TiO2/s was also prepared, and it showed an obvious temperature adjustment, and the service life can last for 14 years under normal weather conditions. Not limited to the prepared multilayer film systems, the methodology used here is also suitable for the fast development of other multilayer film systems.

New multilayer film photonic crystal grating multilayer anti-reflection layer for visible-near-infrared solar cells

In this paper, a new anti-reflection layer(ARL) is designed by the finite element method, which is made of parabolic air slots with periodic distribution etched on a multilayer film structure with optimized thickness. The effective transmissivity in the 400–1450 nm band is formulated in conjunction with the AM1.5 solar spectrum, and the effects of the air slot depth (H), depth-to-width ratio, and the size of a period (T) on the transmissivity of the ARL are investigated separately. By optimizing the structural parameters, a new type of ARL with H = 310 nm and T = 105 nm acting in the 400–1450 nm waveband was obtained. The transmissivity of this stacked structure ARL is improved and the stability of the transmission effect in the full waveband is enhanced compared to the conventional membrane structure and the emerging micro-nano-optical structure. The effective transmissivity of this multilayer film photonic crystal grating ARL is calculated to be 98.43% in the operating full waveband (400–1450nm) of the Si-0.86 eV PbS double-junction solar cell. The transmissivity is higher than 93.83% of multilayer film ARL and 97.13% of TiO2 grating ARL.

Calculation and properties of thermal stress of monolayer film and solution of thermal stress of multilayer infrared antireflection coating by finite element analysis

The deposition of infrared antireflection coatings on silicon lenses is a widely practiced technique that has been extensively investigated by researchers over an extended period. Thermal stress is essential to the adhesion between the film and the substrate. To measure the magnitude of thermal stresses, we use the mechanical analysis method to convert thermal stresses into shearing and peeling stresses. Expressions for these two stresses are then derived. Then, we analyzed the effect of the monolayer film's properties on the silicon substrate's stress. The results indicate that peeling stress is the main factor affecting the adhesion between the film and the substrate, and various approaches can be employed to successfully mitigate the peeling stress exerted on the substrate. The influence of the multilayer film's structure on the peeling stress experienced by the silicon substrate was investigated through the utilization of finite element analysis. In this study, three distinct infrared antireflection coatings were deposited on silicon substrates individually. Subsequently, these coated substrates underwent rigorous environmental testing. The findings from this testing confirmed the accuracy of the stress analysis results obtained by finite element analysis for the multilayer film. Our research has resulted in solutions for determining the magnitude of shearing and peeling stress. We have employed finite element analysis to identify a suitable structure for an antireflection coating that exhibits minimal peeling stress. This advancement has the potential to improve the effectiveness of design processes and the adaptability of infrared antireflection coatings in various environmental conditions.

Laser-compatible infrared stealth metamaterial based on high-temperature resistant metal

In this paper, we design a metamaterial film with multilayer structure for laser-compatible infrared stealth. The multilayer film structure is formed by stacking the high-temperature resistant metal Mo and Ge. Numerical results indicate that the absorptivity is 80.42 % and 96.92 % at 1.06μm and 1.55μm, respectively and the average emissivity of 35μm and 812μm atmospheric window bands are lower than 20 %. At the same time, there is a wide-band resonant absorption peak at the 5 ∼ 8 μm non-atmospheric window band which is beneficial for radiant heat dissipation. The effects of film thickness, polarization of incident light as well as incident angles on stealth performance are studied. The designed structure is only composed of four layers, which is easy to fabricate by film deposition and to realize large-scale integration, and has a very broad application prospect.

Synergistic effects of EDTA and lysozyme on the properties of hydroxypropyl starch nano antibacterial films

Hydroxypropyl starch (HPS) nano antibacterial films incorporating Ethylene Diamine Tetraacetic Acid (EDTA) and lysozyme (LY) were fabricated via solvent casting method. The synergistic effects of EDTA and LY on the microstructure, component interactions, color, optical, mechanical, barrier and antibacterial properties of HPS nano antibacterial films were evaluated. The results indicated that EDTA and LY were well dispersed in the matrix of the HPS nano antibacterial films, the film-forming substrates have good compatibility, resulting in a dense multi-layer structure of the HPS nano antibacterial films. The addition of EDTA and LY increased the color parameters (L*, a*, b* and △E*) of the HPS nano antibacterial films. The synergistic effects of EDTA and LY significantly decreased the light transmission of the HPS nano antibacterial films. The presence of EDTA and LY increased the tensile strength (TS) and the elongation at break (EAB) of the HPS nano antibacterial films. The TS and EAB of E2.5L1 reached the highest values of 6.329 MPa and 50.24 %, respectively. The incorporation of EDTA and LY had positive effects on the improvement of water vapor permeability (WVP) and oxygen permeability (OP). The WVP and OP of E2.5L1 reached the highest values of 0.9350 × 10−12 g cm/cm2•s•Pa and 0.297 × 10 −2 g m/m2 •d, respectively. In addition, EDTA and LY had significant synergistic effects on the antibacterial activity against S. aureus (Gram-positive bacteria) and E. coli (Gram-negative bacteria). E2.5L1 exhibited the highest antibacterial activity and the inhibition zone diameters of S. aureus and E. coli were 3.69 mm and 4.28 mm, respectively. The HPS nano antibacterial films incorporating EDTA and LY are potential functional packaging materials.

Electric field-assisted dissolution of bimetal-dielectric multilayer systems

The electric field-assisted dissolution (EFAD) of Ag and Au metal island films (MIFs) in multilayer structures is investigated. The samples consist of Au and Ag MIFs separated by SiO2 layers deposited on soda-lime glass substrates. The samples were subjected to two types of process: a) thermal annealing at 200°C, and b) application of 500 V dc voltage at 200°C. Spectroscopic ellipsometry and secondary ion mass spectrometry were used to track sample changes. It is shown that thermal annealing induces ion exchange between Ag and Na ions from the glass, leading to partial dissolution of Ag MIFs and Ag being incorporated in the glass and Au MIFs. EFAD process leads to the partial or complete dissolution of Ag films depending on the process duration, while Au dissolution turns out to be more difficult. The optical properties are consistent with the compositional changes and additionally suggest MIF morphology modifications. Numerical simulations of ion drift and diffusion reveal the importance of ion exchange during thermal annealing to enable an efficient MIF dissolution. Overall, the study helps to understand the EFAD of different metals in complex systems and provides insights for the application of this technique in systems containing several metals.

Development of multilayer PVA-MMT and PVA-CS film structures by spin coating-assisted layer-by-layer technique: Effect of PVA, CS and MMT nanoclay orientation on oxygen barrier properties

The orientation of biopolymer macromolecules and nanoclay, specifically Montmorillonite (MMT) nanoplatelets, plays a crucial role in controlling the properties of multi-layer film structures. Understanding the impact of macromolecule and nanoclay platelets’ orientation on barrier properties of packaging films is essential. To investigate the influence of hydrogen bonding in multilayer films structures, two polymers, namely polyvinyl alcohol (PVA) and chitosan (CS), were selected and laminated nanocomposite films were fabricated using the spin coating-assisted layer-by-layer (Spin-LbL) assembly technique. This technique facilitates the production of highly oriented nanocomposite films, where polymer chains and nanoclay particles align parallel to the film surface. Multi-directional 2-D wide-angle X-ray diffraction (2D-WADX) was successfully used to accurately assess the orientation and distribution of MMT nanoplatelets. Additionally, the films underwent characterization using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The 2D-WADX analysis revealed a parallel alignment of both the PVA chains and MMT clay nanoplatelets parallel to film surface. The XRD results confirmed the formation of intercalated nanolaminate structures, hydrogen-bonding interactions, and adjustments in the crystalline structure of PVA matrix. Through contact angle and oxygen permeability measurements, we observed that all quadri-layer film structures exhibited hydrophobic properties and reduced oxygen permeability compared to neat PVA films. Furthermore, the integration of MMT nanoclay, even at low concentrations, contributed to the development of nanocomposite films with improved oxygen barrier properties. Consequently, the quadri-layer films demonstrate great potential for food packaging applications.

Designing vibrant and bright transmission colors with multilayer film structures

In this work, we present a multilayer film structure that utilizes optical resonance for preparing extremely efficient and highly saturated red, green, and blue transmittance colors. Based on numerical simulations and analysis, it is demonstrated that the structure produces R, G, and B colors with a purity approximately comparable to that of standard RGB colors and that a rich variety of structural colors can be obtained while maintaining efficient transmission efficiency. In addition, a metallic interlayer is introduced into the transparent dielectric cavity to selectively suppress resonances in the short-wavelength region, thereby improving the purity of the red color. Finally, we investigate the effect of the incidence angle on color purity and transmission efficiency. This study introduces a rapid and efficient method for producing high-quality structural colors, expanding their versatile applications in optics, materials science, and energy fields.

Comparison of properties of multilayer film sputtered on glass and polypropylene substrates with angular DC magnetron Co-sputtering system

Complex multilayer film structures were fabricated through a custom-built angular DC magnetron co-sputtering system. In this system, separate Cu, Al, and brass (Cu + Zn) targets were mounted on three magnetron guns, working in conjunction with a rotating substrate. This study aimed to compare the properties of films with intricate structures, which were sputtered onto glass slides and polypropylene substrates. The sputtering process was optimized using a Box–Behnken design, considering three variable operating conditions: substrate rotation speed, sputtering time, and sputtering voltage. The Analysis of Variance (ANOVA) results for film thickness and roughness, sputtered with three different materials onto glass slides and polypropylene (PP) substrates, indicated that all three independent variables significantly influenced the optimum response, with P-values less than 0.05 (<α = 0.05). The optimal conditions for maximizing the thickness and roughness of the sputtered film on PP substrates differed from those obtained for the thin-film properties of the sputtered film on glass slide substrates. Top-view images of the surface morphology revealed a dense and granular structure for the film deposited on the glass slide, whereas some grooves between the grains and fractures were observed in the film on the PP substrate.Additionally, it was evident that these sputtered multilayer films exhibited a complex structure, as reflected in the uniform and homogeneous distribution of Cu, Al, and Zn atoms on both glass slides and PP substrates.

Optical, Electrical and Structural Properties of ITO/IZO and IZO/ITO Multilayer Transparent Conductive Oxide Films Deposited via Radiofrequency Magnetron Sputtering

In this study, we investigated the potential of multilayer TCO structures, specifically those made up of Indium Tin Oxide (ITO) and Indium Zinc Oxide (IZO), for crystalline silicon heterojunction solar cells (SHJ). We used the radiofrequency (RF) magnetron sputtering method to deposit various thin-film structures under various deposition temperatures and evaluated their electrical, optical, and morphological properties. The objective was to obtain films with lower sheet resistances and higher transmittances than those of single-layer thin films. Our results show that the ITO/IZO/ITO/IZO/ITO multilayer film structure deposited at 200 °C achieves the best sheet resistance of 18.5 Ohm/sq and a high optical transmittance of over 90% at a 550 nm wavelength. This indicates that multilayer TCO structures have the potential to be more optically and electrically efficient, and that they can improve the performance of optoelectronic devices. Finally, a power conversion efficiency of 17.46% was obtained for a silicon heterojunction (SHJ) solar cell fabricated using an ITO/IZO/ITO/IZO/ITO multilayer film structure deposited at 200 °C as a front TCO. Our study provides valuable insights into the field of TCOs and offers a promising avenue for future research.

Surface forces and friction between Langmuir-Blodgett polymer layers in a nonpolar solvent

Optimization of boundary lubrication by tuning the confined molecular structures formed by surface-active additives such as surfactants and polymers is of key importance to improving energy efficiency in mechanical processes. Here, using the surface forces apparatus (SFA), we have directly measured the normal and shear forces between surface layers of a functionalised olefin copolymer (FOCP) in n-dodecane, deposited onto mica using the Langmuir-Blodgett (LB) technique. The FOCP has an olefin backbone decorated with a statistical distribution of polar-aromatic groups, with a structure that we term as “centipede”. The effect of lateral confinement, characterised by the surface pressure, Πdep, at the air–water interface at which the LB films are transferred, was examined. Normal force profiles revealed that the thickness of the LB films increased significantly with Πdep, with the film thickness (t > 20 nm) inferring a multi-layered film structure, consistent with the interfacial characterisation results from synchrotron X-ray reflectivity (XRR) measurements. The coefficient of friction, µ, between the LB films spanned two orders of magnitude from superlubricity (µ ∼ 0.002) to much higher friction (µ > 0.1) depending nonlinearly on Πdep, with the lowest friction observed at the intermediate Πdep. Molecular arrangement upon LB compression leads to the multilayer film with a structure akin to an interfacial gel, with transient crosslinking facilitated by the intra- and inter-molecular interactions between the functional groups. We attribute the differences in frictional behaviour to the different prevalence of the FOCP functional groups at the lubricating interface, which depends sensitively on the degree of compression at the air–water interface prior to the LB deposition. The LB films remain intact after repeated compression (up to pressures of 10 MPa) and shear cycles, indicating strong surface anchorage and structural robustness as a load-bearing and shear-mediating boundary layer. These unprecedented results from the friction measurements between LB films of a statistical copolymer in oil point towards new strategies for tailoring macromolecular architecture for mediating efficient energy dissipation in oil-based tribological applications.