Multilayer Nanostructures Research Articles

Cadmium-Free Nanostructured Multilayer Thin Films with Bright Blue Photoluminescence and Excellent Stability

Cadmium-based quantum dots (Cd-QDs) show decent performance for lighting applications due to good color saturation, an excellent high quantum yield, and a narrow full-width at half-maximum. However, the intrinsic toxicity of Cd is a major hindrance to related applications, especially in the biological field. ZnSe, with a band gap of 2.7 eV and lower toxicity than CdSe or CdS, is promising as a blue luminescent material. Herein, we mainly reported the preparation and luminescence properties of nanostructured ZnSe/ZnS multilayer thin films with bright blue photoluminescence. The photoluminescence spectrum contained two emission peaks, located at about 442 nm (near band-edge emission) and 550 nm (defect-related emission), respectively. More importantly, the photoluminescence performance and decay were explored in detail through low-temperature photoluminescence spectra. In addition, the nanostructured ZnSe/ZnS multilayer thin films showed favorable photostability.

Two-step maskless fabrication of compound fork-shaped gratings in nanomultilayer structures based on chalcogenide glasses.

We demonstrate an easy two-step maskless method for the fabrication of so-called compound fork-shaped gratings in nanomultilayer structures (NMLSs) based on chalcogenide glasses. Such elements allow one to generate different configurations of optical vortex (OV) beams with given topological charges (TCs). The used NMLS is particularly interesting because it enables one to realize the direct one-step writing of the surface relief without selective etching. We show that it is possible to control TCs of the generated OV beam arrays, their locations, and intensity. The proposed approach can easily be adapted to the fabrication of compound diffractive gratings performing the desired one- and two-dimensional generation and splitting of other structured laser beams.

Computing Vertex Degree-Based Multiplicative Version of Topological Indices for Tungsten Trioxide Nano Multilayer Structure in Nanotherapeutic Anti-Cancer Activity

Several research reports suggest that there is a strong interdependence among the molecular structure of chemical compounds and their physicochemical properties. The computation of the topological index of such a chemical structure facilitates researchers to gain more insight into the physical and bio-activity of chemical materials. In this article, we focus on WO3, which is a widely studied nanomaterial and is recently employed as an excellent cytotoxic agent towards the liver (Hep–2) and the breast (MCF–7) cancerous cells. Various vertex degree-based multiplicative versions of topological indices for WO3 nano multilayer were computed using the edge partition technique. We also compared all of the indices graphically. The obtained results redress the lack of medical and chemical experiments, thus constructing the theoretical framework for the pharmacological field.

Multilayer core-shell nanostructures for enhanced 808 nm responsive upconversion

The construction of core-shell structure is an effective strategy for promoting the emission efficiency of upconversion nanocrystals (UCNCs). In this work, the UCNCs based on Nd-doping with a multilayer core-shell nanostructure are fabricated toward achieving efficient upconversion for 808 nm excitation, which have great potential for optical applications, especially photobiological applications.

The tribo-corrosion behavior of monolayer VN and multilayer VN/C hard coatings under simulated seawater

The monolayer VN as well as multilayer VN/C coatings were obtained on 316 L steel via physical vapor deposition (PVD) technology. Structure, mechanical property and tribo-corrosion behavior of monolayer VN and multilayer VN/C coatings under simulated seawater were estimated by corresponding detection equipment. After analysis, C nanolayer could break the grain growth of VN phase, which would enhance the coating toughness and inhibit the source of crack. At the same time, the multilayer structure interface could suppress the dislocation movement. In tribo-corrosion process, the corrosion current density (icorr) of VN/C coating was 2.71 × 10−6 A/cm2, which was 70.47% lower than that of VN coating (9.18 × 10−6 A/cm2), implying that the nano-multilayer structure of VN/C coating showed a strong barrier effect on corrosion medium. Moreover, the C nanolayer not only suppressed the permeation of simulated seawater, but also formed the transfer film to protect the substrate. Thus, the multilayer VN/C coating revealed stronger anti-wear and anti-corrosion abilities than the monolayer VN coating.

Spider-Web and Ant-Tentacle Doubly Bio-Inspired Multifunctional Self-Powered Electronic Skin with Hierarchical Nanostructure.

For the practical applications of wearable electronic skin (e‐skin), the multifunctional, self‐powered, biodegradable, biocompatible, and breathable materials are needed to be assessed and tailored simultaneously. Integration of these features in flexible e‐skin is highly desirable; however, it is challenging to construct an e‐skin to meet the requirements of practical applications. Herein, a bio‐inspired multifunctional e‐skin with a multilayer nanostructure based on spider web and ant tentacle is constructed, which can collect biological energy through a triboelectric nanogenerator for the simultaneous detection of pressure, humidity, and temperature. Owing to the poly(vinyl alcohol)/poly(vinylidene fluoride) nanofibers spider web structure, internal bead‐chain structure, and the collagen aggregate nanofibers based positive friction material, e‐skin exhibits the highest pressure sensitivity (0.48 V kPa−1) and high detection range (0–135 kPa). Synchronously, the nanofibers imitating the antennae of ants provide e‐skin with short response and recovery time (16 and 25 s, respectively) to a wide humidity range (25–85% RH). The e‐skin is demonstrated to exhibit temperature coefficient of resistance (TCR = 0.0075 °C−1) in a range of the surrounding temperature (27–55 °C). Moreover, the natural collagen aggregate and the all‐nanofibers structure ensure the biodegradability, biocompatibility, and breathability of the e‐skin, showing great promise for practicability.

Tailoring Helicity Angle of Twisted Skyrmions in Multilayered Nanostructures

Twisted skyrimons (TSs) are intermediate states between Bloch skyrmions and Néel skyrmions, and can emerge in multilayered systems due to the competition between Dzyaloshinskii–Moriya interaction and magnetic dipole–dipole interaction. Herein, TSs are investigated in terms of helicity angle variation and layer dependence in both three layer and general multilayer nanostructures. The tailoring of helicity angle from 0 to π is achieved by stacking the number of magnetic layers and controlling the relative position of each layer. In addition, the precise spatial range where TSs exist stably and the influence of layer and spacer thickness are also discussed. The results provide a fundamental understanding of TSs in multilayered nanostructures, which is significant for the development of skyrmion‐based devices.

Current-induced dynamics of skyrmion tubes in synthetic antiferromagnetic multilayers

Topological spin textures can be found in both two-dimensional and three-dimensional nanostructures, which are of great importance to advanced spintronic applications. Here we report the current-induced skyrmion tube dynamics in three-dimensional synthetic antiferromagnetic (SyAF) bilayer and multilayer nanostructures. It is found that the SyAF skyrmion tube made of thinner sublayer skyrmions is more stable during its motion, which ensures that a higher speed of the skyrmion tube can be reached effectively at larger driving current. In the SyAF multilayer with a given total thickness, the current-induced deformation of the SyAF skyrmion tube decreases with an increasing number of interfaces; namely, the rigidity of the SyAF skyrmion tube with a given thickness increases with the number of ferromagnetic (FM) layers. For the SyAF multilayer with an even number of FM layers, the skyrmion Hall effect can be eliminated when the thicknesses of all FM layers are identical. Larger damping parameter leads to smaller deformation and slower speed of the SyAF skyrmion tube. Larger fieldlike torque leads to larger deformation and a higher speed of the SyAF skyrmion tube. Our results are useful for understanding the dynamic behaviors of three-dimensional topological spin textures and may provide guidelines for building SyAF spintronic devices.

Multifunctional nanolayered renewable carbon for electromagnetic interference and energy devices

Controlled carbonization of biomass leads to nanolayered graphitic structures with characteristic crystalline sp2 hybridization, conductive properties up to 600 S/m, and electromagnetic interference shielding effectiveness of 47.7 dB at 12 GHz. We investigate functional properties of nanolayered renewable carbon, including conductive and photoluminescent features, leading to a new understanding of structure–property correlation and their graphitic multilayered nanostructures. Some unique and novel behaviors, such as negative dielectric factors, hold promise in the areas of cofactor sensors and electromagnetic interference shielding due to their correlation with the absorption of microwave radiation. An electromagnetic interference device demonstrates an application of these nanographitic carbon materials. These conductive and photoluminescent carbon materials hold significant promise in applications such as power electronics, batteries, and sensors, where they may replace conventional metal and graphene.

Controlling Nanostructure in Inkjet Printed Organic Transistors for Pressure Sensing Applications.

This work reports the development of a highly sensitive pressure detector prepared by inkjet printing of electroactive organic semiconducting materials. The pressure sensing is achieved by incorporating a quantum tunnelling composite material composed of graphite nanoparticles in a rubber matrix into the multilayer nanostructure of a printed organic thin film transistor. This printed device was able to convert shock wave inputs rapidly and reproducibly into an inherently amplified electronic output signal. Variation of the organic ink material, solvents, and printing speeds were shown to modulate the multilayer nanostructure of the organic semiconducting and dielectric layers, enabling tuneable optimisation of the transistor response. The optimised printed device exhibits rapid switching from a non-conductive to a conductive state upon application of low pressures whilst operating at very low source-drain voltages (0–5 V), a feature that is often required in applications sensitive to stray electromagnetic signals but is not provided by conventional inorganic transistors and switches. The printed sensor also operates without the need for any gate voltage bias, further reducing the electronics required for operation. The printable low-voltage sensing and signalling system offers a route to simple low-cost assemblies for secure detection of stimuli in highly energetic systems including combustible or chemically sensitive materials.

Multilayered L-shaped nanoantenna arrays with an increased electric field enhancement

The performance of the composite metal/dielectric multilayered L-shaped nanoantennas for strong electric field enhancement has been investigated. The bonding and antibonding modes arising from the plasmon hybridization modes of the multilayered nanoantennas are presented. It is observed that the plasmon coupling of the proposed composite nanostructures can form three states of in-phase bonding, out-of-phase bonding and out-of-phase antibonding. The out-of-phase charge distribution indicates that dark plasmon modes can be revealed on the bonding modes of the proposed multilayered structures. The response of the proposed L-shaped nanoantennas to the attachment of a dielectric spherical nanoparticle and their molecular sensitivity are investigated. According to this study, the proposed multilayered nanostructures are good candidates for strong electric field localization in sensing and detection applications.

Microstructure and High-Temperature Friction and Wear Properties of CrAlMoN Film

Closed-field unbalanced magnetron sputtering ion plating was used to form CrAlMoN films on the surface of single-crystal silicon and tool steel. The composition and morphology of the films were determined through energy-dispersive X-ray spectroscopy, scanning electron microscopy, and transmission electron microscopy. High-temperature friction and wear properties of CrAlMoN films were assed using a friction and wear tester and by studying the film cross-sections. The hardness of CrAlMoN films was determined using a nanoindenter. Results showed that CrAlMoN films have a nanomultilayer structure, with the same fcc structure as CrN. At room temperature, the hardness and wear resistance of CrAlMoN films are greater than that of CrAlN films. The friction properties of CrAlMoN films varied widely with an increase in the temperature. At 600 °C, the friction performance of CrAlMoN films degrades rapidly, and the degree of film wear is significantly increased. In contrast, CrAlN films retain high wear resistance at 600 °C.

Strong coupling between in-plane photonic modes and out-of-plane plasmonic modes in 2D metal–dielectric–metal nanocylinder arrays

Arrays of metal–dielectric–metal (MDM) multilayer nanostructure can support various kinds of plasmonic modes including in-plane (IP) localized/delocalized surface plasmons or lattice resonances, photonic waves, as well as out-of-plane (OP) plasmon modes. Hybridization between different modes offers rich physics such as lasing, sub- and super-radiant modes, and efficient light absorption. While interplays between different sets of in-plane modes have been intensively investigated, the interaction between in-plane and out-of-plane modes is rarely explored. Here, we propose a MDM nanostructure with 2D nanocylinder array and study in detail the strong coupling between the in-plane photonic modes at the dielectric layer and the out-of-plane plasmon modes excited at the cylinder sidewalls. We demonstrate the strong coupling between the localized second-order IP mode and the first-order OP mode with a Rabi splitting up to 250 meV in the near-infrared region. A new IP mode arising from the radiative field can induce another kind of strong coupling with OP modes as the cylinder radius is larger than 98 nm. The underlying physics within this plasmon–photon system is quantitatively revealed by the coupled oscillator model and calculated E-field distribution. The proposed MDM system provides a good platform for investigating multimode coupling and nano-optics devices.

Metrological studies of the characteristics of multilayer surface coatings using synchrotron radiation

The investigations of multilayer surface nanostructures characteristics was performed with synchrotron radiation sources, characterized by an intensive, calculated continuum. It plays an important role in nanoelectronics metrological base. The main research were carried out at electron storage rings «Siberia-1» (Kurchatov Institute) and MLS (PTB, Berlin) with low electron energy, in a wide wavelength range, including visible range, AUV, VU, EUV and to exclude the X-ray radiation influence. The methods of the radiometers, photodiodes, filters and multilayer mirrors characteristics measurements are based on the synchrotron radiation absolute spectral characteristics and accelerated electrons number variation. The metrological investigations with synchrotron radiation was concentrated on: – absolute spectral responsivety of silicon photodiodes with multilayer filters for integral radiometers applications; – spectral transmittances of surface layers of photodiodes in the extreme ultraviolet region; – spectral reflectance coefficient of superlattice. The characteristics of photodiodes and filters on a synchrotron radiation source are measured using a monochromator and a reference detector. The use of a synchrotron radiation channel makes it possible to study the spectral transmittance of thin films and multilayer structures formed in the in situ mode. To form multilayer nanostructures directly on the receiving surface of photodetectors, an ion-plasma sputtering module is used. The optical scheme of the channel provides for the possibility of using monochromators of grazing incidence for the range of photon energies from 25 to 100 ev and normal incidence for the range of photon energies from 4 to 25 ev. At a photon energy of 40 ev, the absolute spectral sensitivity was 70 ma / W for a photodiode with a surface multilayer filter applied. To develop an experimental technique for measuring the spectral reflection coefficient of multilayer mirrors, and to create standard samples, the Mo/Si system was studied. Computer modeling of multi-layer coatings allows us to calculate the optical characteristics of superlattices in the extreme ultraviolet region. The obtained results of measurements of the spectral reflection coefficient of a multilayer coating in the photon energy range of 65–100 ev indicate a resonance reflection character with a max-imum at an energy of 83.5 ev and an energy width at a half-height of about 6.5 ev. The working wave-length of the reflecting mirror corresponds to the calculated one, which confirms the effectiveness of the adopted model.

Machine-learning based interatomic potential for studying of crystal structures properties

In the process of modeling multilayer semiconductor nanostructures, it is important to quickly obtain accurate values the characteristics of the structure under consideration. One of these characteristics is the value of the interaction energy of atoms within the structure. The energy value is also important for obtaining other quantities, such as bulk modulus of the structure, shear modulus etc. The paper considers a machine learning based method for obtaining the interaction energy of two atoms. A model built on the basis of the Gaussian Approximation Potential (GAP) is trained on a previously prepared sample and allows predicting the energy values of atom pairs for test data. The values of the coordinates of the interacting atoms, the distance between the atoms, the value of the lattice constant of the structure, an indication of the type of interacting atoms, and also the value describing the environment of the atoms were used as features. The coordinates of the atoms, the distance between the atoms, the lattice constant of the structure, an indication of the type of interacting atoms, the value describing the environment of the atoms were used as features. The computational experiment was carried out with structures of Si, Ge and C. There were estimated the rate of obtaining the energy of interacting atoms and the accuracy of the obtained value. The characteristics of speed and accuracy were compared with the characteristics that were achieved using the many-particle interatomic potential — the Tersoff potential.

Lithographically Defined Cross-Linkable Top Coats for Nanomanufacturing with High-χ Block Copolymers.

The directed self-assembly (DSA) of block copolymers (BCPs) is a powerful method for the manufacture of high-resolution features. Critical issues remain to be addressed for successful implementation of DSA, such as dewetting and controlled orientation of BCP domains through physicochemical manipulations at the BCP interfaces, and the spatial positioning and registration of the BCP features. Here, we introduce novel top-coat (TC) materials designed to undergo cross-linking reactions triggered by thermal or photoactivation processes. The cross-linked TC layer with adjusted composition induces a mechanical confinement of the BCP layer, suppressing its dewetting while promoting perpendicular orientation of BCP domains. The selection of areas of interest with perpendicular features is performed directly on the patternable TC layer via a lithography step and leverages attractive integration pathways for the generation of locally controlled BCP patterns and nanostructured BCP multilayers.

Influence of Mo Doping on the Microstructure, Friction, and Wear Properties of CrAlN Films

In this study, closed-field unbalanced magnetron sputtering ion-plating technology is used to deposit CrAlMoN and CrAlN nanomultilayer films on the surfaces of M2 tool steel and single-crystal Si. Energy-dispersive spectroscopy, scanning electron microscopy, x-ray photoelectron spectroscopy, transmission electron microscopy, x-ray diffraction, scratch tester, nanoindenter, and pin-on-disk wear tester are used to study the influence of Mo doping on the composition, microstructure, mechanical properties, and friction properties of CrAlN films. Results show that CrAlMoN films have a nanomultilayer structure, CrN/Mo2N/CrN/AlN, with a modulation period of 10.5 nm. After Mo doping, the face-centered cubic structure of CrAlMoN films remains the same as that of CrAlN films. The chemical valence of each element in CrAlN films does not change with Mo doping. At room temperature, the wear resistance of CrAlMoN films is significantly improved compared with that of CrAlN films. This is attributed to the significant antifriction effect of MoO3 that forms on CrAlMoN films doped with Mo during the friction process.

Dispersion manipulation of multilayer dielectric plasmonic metasurfaces

We theoretically investigate metasurfaces consisting of multilayered dielectric nanostructures periodically positioned on a metal substrate. The characteristics of the metasurface are determined by the dispersion of the multilayered surface-plasmon-dielectric-polariton systems. We manipulated the dispersion in two ways. First, the dispersion curve can be arbitrarily tailored by changing the dielectric thicknesses and refractive indices. Second, the plasmonic band structure of a periodically corrugated multilayer dielectric is introduced. Based on these two manipulations, we show that this system is tailored in momentum space. We also provide an example of broadband absorption. When the substrate metal is replaced by a graphene monolayer, the band structure of graphene plasmons can be tailored by multilayer dielectric at infrared frequencies. As a result, high optical absorption enhancement in graphene can be realized over a wide angular range in a narrow band. This method may be employed in optical absorption and solar cells.

2D Accordion‐like MXene Nanosheets as a Sensitive Electrode Material for Baicalin Sensing

AbstractHerein, accordion‐like MXene nanosheets was used as electrode sensing material for baicalin determination in traditional Chinese medicine preparation for the first time. The consecutive multilayer nanostructure of MXene observably enhanced the electroactive surface area of electrode and accelerated the electron transfer rate to acquire outstanding electrochemical response to baicalin. The electrode process of baicalin and relative dynamic parameters were investigated using cyclic voltammetry and chronocoulometry. Under optimized conditions, a good linear relationship was achieved between the response current and baicalin levels over the range of 0.08–60 μM with a detection limit of 26 nM (S/N=3). The developed sensor was successfully applied for baicalin monitoring in traditional Chinese medicine preparation and human urine samples.

Mechanically and chemically robust molybdenum carbide-graphene hybrid conductors

Although transition metal carbides (TMCs) exhibit intriguing physical and chemical properties, a central issue for multifaceted applications based on TMC materials is to meet a large-scale and reliable synthetic route of air-stable TMC materials. Here, the primary aim is to address the issues by synthesizing Mo2C encapsulated with multilayer graphene coral-like nanostructure. The oxidation stability of Mo2C can be effectively compensated by the complementary hybridization of multilayer graphene, which serves as a perfect chemical barrier. Large-scale graphene/Mo2C can be readily synthesized on commercial Mo foils by surface-oxidation-mediated chemical vapor deposition. Explicit structural and chemical evaluation was implemented to explore the structural and chemical manipulation of Mo2C by selecting the starting material (Mo or MoO3). Differences in the thickness of the oxide layers on the Mo surface led to structural and material diversities for the formation of Mo2C with nanogranular and graphene/Mo2C coral-like nanostructures. The capability of graphene/Mo2C for applications in nanostructured electrodes and heaters was validated by its extraordinary electrical conductivity, substantial enhancement in chemical durability and mechanical flexibility, and outstanding performance of deformable heaters.