Narrow Results

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.

The novel modification of gold surfaces with a biotinylated polypeptide multilayer formed by nonspecific electrostatic adsorption was designed for the SPR sensing platform. The multilayer of polypeptides (poly-L-lysine and poly(aspartic acid)) was prepared onto a negatively charged self-assembled monolayer of 11-mercaptoundecanoic acid (MUA) on gold film. The polypeptide multilayer was functionalized with biotin by directly grafting to poly(succinimide) (PSI). The specific binding of avidin to the biotinylated polypeptide multilayer (DS 2.7%) resulted in a shift in the refractive index of 0.003±9×10^-4 with a surface density of 2.9 ng/mm². This multilayer surface was found to provide a simple and effective method for the SPR sensing.

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.