Narrow Results

IZO films were deposited onto polyethylene terephthalate (PET) substrate at room temperature by the inclination opposite target type DC magnetron sputtering equipment. In this paper, SiO or SiON thin films of about 20nm thickness were introduced as buffer layers between the IZO thin films and the PET substrate. Electrical resistivity, transmittance and surface uniformity properties were investigated. It is clear that the film surface roughness of multilayer thin films was less than that of IZO monolayer thin films. The surface average roughness (Ra) of the multilayer film with 230nm IZO layer thickness was about 1.6nm, and that of IZO monolayer film was 2.4nm. All of the multilayer samples had high optical transmittance (about 90%) in the visible region. Of particular note, the transmittance of multilayer films was slightly higher than that of monolayer films when the IZO layer was thicker than 200nm. High electrical conductivity was also achieved with thick films.

The cobalt-nickel/copper multilayer films were prepared by electrodeposition process in sulfate solution using a three electrode cell. Cyclic voltammetry and double chronoampermetry techniques were utilized to characterize the multilayer system and to obtain the nucleation and growth mechanism. The cyclic voltammograms determined the reduction potential range of the three components and also clearly emphasized that electrodeposition of cobalt-nickel alloy was controlled by a kinetic process, while copper ions were reduced with diffusion-controlled mechanism. These results were confirmed with those which were extracted from the chronoampermetry curves. In addition, the current transients revealed that nucleation mechanism was a typical three-dimensional nucleation process. The Atomic Force Microscope images (AFM) of these multilayers also confirmed the three-dimensional nucleation mechanism. The compositional analysis of these multilayers was carried out by Atomic Absorption Spectroscopy (AAS) and X-ray Photoelectron Spectroscopy (XPS) methods. The bulk and surface compositional analysis both revealed that the amount of Copper component within the cobalt-nickel layers is less than 3%.

Relatively low strength and fracture toughness of ceramics have restricted their applications. Various solutions have been studied to overcome the abovementioned drawbacks. One of the most sophisticated and promising solution is production of multilayer ceramic composites. High hardness, heat and wear resistance, low electrical and thermal conductivity, and resistance to chemical attacks are the most important characteristics of Al₂O₃. Therefore, it is a common candidate for various industrial applications. Multilayer alumina-zirconia composites were made using two methods of isostatic and hydraulic compaction of dry ceramic powders. The green articles were conventionally sintered at 1420, 1550 and 1650°C for 3h. The microstructure and density of composites were investigated. The results show that the pressing method and sintering temperature have a relatively moderate effect on the microstructure and density of the sintered samples.

Self-assembled films of organic dye Chicago Sky Blue 6B (CSB) have been fabricated onto solid substrate by electrostatic alternate adsorption of polycation ploy(allylamine hydrochloride) (PAH) and CSB. UV–Vis absorption spectroscopic studies reveal the successful incorporation of CSB molecules into Layer-by-Layer (LbL) films and consequent formation of aggregates. This view is supported by FTIR spectroscopic studies. Scanning electron microscope picture confirms the formation of nanocrystalline aggregates in the LbL films. About 15 min is required to complete the electrostatic interaction between PAH and CSB molecules in one bilayer LbL film.

Layer-by-Layer (LBL) self-assembled films of rose bengal (RB) have been fabricated onto quartz substrate by the alternative adsorption of polycation poly (amine hydrochloride) (PAH) and RB. UV–Vis absorption studies reveal the formation of RB dimmer in PAH-RB LbL films. Scanning Electron Micrograph (SEM) picture confirms the aggregation of RB molecules in LbL films. Almost 15 min is required to complete the interaction between RB and PAH molecules in the 1 bilayer LbL film. The dye (RB) was found to come off the film during the subsequent poly cation (PAH) deposition. As an alternative approach RB was anchored to the polycation PAH via physiadsorption and controlling the concentration of the combination of RB and PAH was used as polycation and poly (acrylic acid) (PAA) as polyanion for film deposition. The absorption spectra after each deposition showed that there was no material loss during layer depositions via second method.

Ga-doped ZnO (GZO)/metal/GZO structures were fabricated on glass substrates to be the transparent conducting layers in this study. GZO films and metal films were deposited at room-temperature by a radio-frequency sputter and a thermal evaporator, respectively. The GZO/Ag/GZO (GAG) structures had poor electrical and optical properties due to the formation of Ag islands on the GZO layer. A 1-nm Cu seed layer was deposited on the GZO layer to fabricate the GZO/Ag/Cu/GZO (GACG) structure to improve its electrical and optical properties. The GACG structure had sheet resistance of 9 $\mathrm{\Omega }$, average visible transmittance of 86% and figure of merit of $2.5\times 10^{-2}$${\mathrm{\Omega }}^{-1}$. In addition, the sheet resistance of the GACG structure kept almost the same after annealing at $300^{\circ }$C in atmosphere for more than 5 h, which showed good thermal stability.

To enhance the near-infrared response of photocathodes in the application of image detection, two kinds of multilayer complex structures of GaAs-based photocathodes are developed by changing the structure of the buffer layer underneath the emission layer, wherein one is the graded bandgap structure, and the other is the distributed Bragg reflector (DBR) structure. The theoretical quantum efficiency suitable for the reflection-mode (r-mode) GaAs-based photocathode with these two kinds of buffer structures are deduced based on one-dimensional continuity equations, among which the reflectivity changing with the wavelength of incident light is considered in particular. By comparison of spectral characteristics of photocathodes with the two different structures, and analysis of cathode structure parameters, it is found that the photoelectric performance of the photocathodes with the two structures are quite different, and the structure parameters especially the thickness of GaAs emission layer have a great impact on the spectral characteristic. The quantum efficiency of photocathode with graded bandgap structure is improved due to the introduction of the built-in electric field and the decrement of interface recombination, while for cathode with DBR structure, the quantum efficiency is improved by the multiple reflection of light between two parallel mirrors in the stack of alternating quarter-wave layers of high and low refractive. The theoretical quantum efficiency calculation and analysis would provide theoretical guidance for the better design of GaAs-based photocathodes.

The segregation of Cu atoms in the Cu/Ni multilayers was investigated by means of the full-potential linearized augmented plane-wave method with the generalized-gradient approximation formula. We investigated the segregation of Cu atoms when the Cu/Ni slab is along the (001) and (111) directions, respectively. The results obtained show that at most one-layer Cu atoms can segregate to the Ni surface when Ni films are deposited on the Cu substrate and the segregation of Cu atoms is not sensitive to the orientation of the Cu/Ni slab surface. The result of Cu segregation is to reduce the vacuum effect.

Antireflection coatings have had the greatest impact on optics. The antireflection (AR) coating is the critically important technology in obtaining high performance of optoelectronic devices. In the present paper, characteristics of the ferroelectric based multilayered antireflection coating systems are investigated. Multilayer antireflection coatings consisting of insulator thin films have been modeled in the region between the 400 nm and 800 nm visible bands of electromagnetic spectrum to reduce reflectance from ferroelectric based substrate.

In this type of antireflection coating we can regulate the optical properties of a system by external electric (or thermal field) and design a broadband low reflection coating system for optoelectronic devices. In order to design and simulate the normal incidence wideband visible multilayer AR coatings, we have developed a Fortran software program based upon Fresnell equations. Different types of layers which are two-different materials like ZnSe and ZrO₂ for even-folded multilayer (two-, four-, six-, eight-, ten-, and twelve-layer) antireflection coatings are used. Ferroelectric material, LiNbO₃ is used as the substrate. The optical thicknesses of each layer are equal to a quarter-wave thick at a certain wavelength.

In this work, multilayer graphene was chosen and modeled in ANSYS software. In the software, it was subjected to bending forces through various bend angles. In order to test for bending, the model is subjected to rigid support on the base side. Then a force is applied on the side on which the angle is provided to simulate Bending. Stress–strain plots were analyzed for various bending angles. The graphene sheet was also subjected to twist forces within the software. In order to test for torsion, the model is subjected to rigid support on both sides. Then a couple is applied on the opposite sides to simulate torsion. Torsional stress and strain measurements were analyzed. The trends were studied and correlations with the material properties of graphene were established. The quest is to identify a magic angle for bend and twist.

Self-Assembly Monolayer (SAM) technique, as a novel and developing technique for fabricating layer-by-layer nanofilm on substrates of various sizes, shapes and materials, has received more and more attention in the areas of light-emitting devices, nonlinear optical materials, conductive films, permselective gas membranes, sensors, modification of electrodes, resistance and printing technique. In comparison with other traditional methods, SAM technique has many significant advantages, including simple process, universality, formation with densely packed, well defined, highly ordered surfaces. This paper will give a review on the recent development in SAM technique.

Our present work deals with the formation and thermal behavior of a nonbulk alloy phase confined within about 8 nm across the interfaces of Au/Cu multilayer systems. These multilayers deposited on silicon and float glass by DC magnetron sputtering have been studied by secondary ion mass spectrometry (SIMS), X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (XTEM). Along with the highly oriented growth of the Cu and Au layers along [111], Cu₃Au alloy was found to be present only at the Cu/Au interfaces in the nonbulk tetragonal D0₂₃ phase. Co-sputtering of Au and Cu under similar conditions produces only conventional fccCu₃Au alloy phases, suggesting that interfacial confinement plays a significant role in producing the novel Cu₃Au alloy phase in gold/copper multilayers. This novel phase is found to form only when the interfacial width is less than 10 nm. The D0₂₃ alloy phase tends to stabilize, rather than transforming to the bulk L1₂ phase, when the multilayer is vacuum-annealed at 150°C. As alloy formation spreads out of the interfaces (on vacuum annealing at 200°C), the dominant alloy is CuAu, consistent with the Cu:Au atomic ratio averaged over the multilayer.

Two sets of multilayer structures consisting of 44 alternating layers of a-SiN_x:H (~ 4 nm and 6 nm) and SiO₂ (5 nm) have been fabricated using the plasma-enhanced chemical vapor deposition (PECVD) technique. The a-SiN_x:H that has a lower bandgap forms the well layer, while the large bandgap SiO₂ forms the barrier layer. A single bulk layer of a-SiN_x:H has also been grown to serve as a reference for comparison with the multilayer structures. The samples were studied using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), spectroscopic ellipsometry (SE), and photoluminescence (PL) techniques. The SE data have been successfully fitted, and the complex refractive indices of the a-SiN_x:H in the bulk and multilayers have been determined. The effects of quantum confinement on the optical bandgap and refractive indices of a-SiN_x:H have been investigated. The results are correlated to the PL spectra of the samples.

This paper is developed to characterize mechanical properties of multilayer coatings for different modulation periods. To that end, Dimensional Analysis Method (DAM) and Finite Element Method (FEM) are applied. Based on these methodologies, two dimensionless forms for the new model are expressed. Numerical nanoindentation tests are carried out for different set properties of multilayer coatings in order to validate the proposed model. Therefore, the mechanical properties of multilayer thin films are identified according to the reverse analysis algorithm. Hence, the input and the identified properties are consistent which ensure the effectiveness and the reliability of the proposed model. Moreover, a case study of Ti-TiN multilayer coating deposited on Zr-based metallic glasses was considered. As a result, the new model is useful for multilayer coatings for different modulation periods and can be used for technological applications.

In this paper, we suggest a design strategy for multilayer hydrogel beams with controllable swelling deformation and bending, which can be used in soft devices. We adopt a constitutive model that considers the entanglement chains of the hydrogel and an analytical method for solving multilayer hydrogel beams is developed. First, the reliability of the design strategy is provided by comparing analytical solutions and numerical results. Then, guided by the above design strategy, we quantitatively investigate hydrogel beams with gradient distribution and study the effects of material and distribution on the deformation and bending behavior of the structures. The results show that under non-gradient distribution, all structures with an odd number of total layers only undergo in-plane expansion, while all those with an even number of total layers undergo expansion and bending. However, this law will be broken at the gradient distribution. The introduction of entanglement chains and gradient distribution strategy increase the range of adjustment for deformation and bending. This work is expected to provide new insights into the design of multilayer hydrogel beams for material–structure–function integration.

Nanoscale multilayers of Cr-Ni coatings were deposited on low carbon steel by pulse electroplating and agitation modulation in chromium (III)-nickel (II) bath. The coatings were characterized by using SEM, EDS, XRD and microhardness techniques. For hardness measurement, the total thickness of the coatings was fixed at 5 μm and the thickness of the monolayers in the coatings varied from 20 to 100 nm. Single chromium and single nickel coatings with similar thickness of 5 μm were also produced by using DC electroplating. Microhardness testing was carried out on the surface of the coatings by using a range of loads from 25 to 1000 gf. A composite hardness model was used to estimate and compare the hardness of the single and multilayer coatings. It was shown that multilayer deposition significantly increases the hardness of the coating and the hardness increases further as the thickness of the nano- monolayers is reduced.

By the use of Monte Carlo simulation, we have investigated the phase diagrams and magnetic properties of a ferrimagnetic Ising multilayer system with mixed spins (1, $1∕2$). The ground-state phase diagrams are first constructed for $T=0K$. To examine the influences of certain physical parameters of the system, namely the exchange interactions, the number of layers and the crystal field, we have studied the thermal behavior of the system magnetizations and the corresponding phase diagrams. The results obtained in this work show the existence of second- and first-order phase transitions and compensation temperatures. Moreover, we have investigated the hysteresis behavior, where the multi-loop phenomena are observed.