Improvement in Strain Sensor Stability by Adapting the Metal Contact Layer

Research on stretchable strain sensors is actively conducted due to increasing interest in wearable devices. However, typical studies have focused on improving the elasticity of the electrode. Therefore, methods of directly connecting wire or attaching conductive tape to materials to detect deformation have been used to evaluate the performance of strain sensors. Polyaniline (PANI), a p-type semiconductive polymer, has been widely used for stretchable electrodes. However, conventional procedures have limitations in determining an appropriate metal for ohmic contact with PANI. Materials that are generally used for connection with PANI form an undesirable metal-semiconductor junction and have significant contact resistance. Hence, they degrade sensor performance. This study secured ohmic contact by adapting Au thin film as the metal contact layer (the MCL), with lower contact resistance and a larger work function than PANI. Additionally, we presented a buffer layer using hard polydimethylsiloxane (PDMS) and structured it into a dumbbell shape to protect the metal from deformation. As a result, we enhanced steadiness and repeatability up to 50% strain by comparing the gauge factors and the relative resistance changes. Consequently, adapting structural methods (the MCL and the dumbbell shape) to a device can result in strain sensors with promising stability, as well as high stretchability.

Постростовые технологии каскадных фотоэлектрических преобразователей на основе A-=SUP=-3-=/SUP=-B-=SUP=-5-=/SUP=--гетероструктур

Investigation and development of the post-growth technology for fabricating multi-junction photovoltaic converters based on GaInP/GaInAs/Ge heterostructure has been carried out. Antireflection coating, ohmic contacts and mesa-structure forming stages have been reviewed. The technology of n+-GaAs contact layer etching with the help of plasma-chemical, liquid and ion-beam etching has been investigated. Antireflection coefficient of radiation from the heterostructure with TiOx/SiO2 (x close to 2) antireflection coating surface was less then 3% in wavelength range 450-850 nm. The value of contact resistance for n- and p-type conductivity was 3E−5 − 3E−6 ohm · cm2, the decrease of photosensitive region shading degree at increased bus-bar conductivity has been archived. The mesa-structure surface current leakage decreased to the value of E-9 A at voltage less then 1 V.

Numerical simulation of electric heating of dispersed-reinforced concrete with steel fibers

Solution to the problem of current density distribution in a fragment of a steel fiber concrete mixture is obtained, using the finite element method. It is shown that the fiber-concrete contact layer makes a significant contribution to the effective electrical conductivity of the mixture. More than 50% of the total current flows through the reinforcing fibers. The conductivity of the mixture increases in proportion to the reinforcement coefficient. It increases 2-3 times, depending on the choice of the contact properties, reinforcing 2% by volume layer. Experimental data that confirm the indicated dependence are presented. Also, a solution to the problem of heat distribution in a fragment of steel-fiber-concrete mixture in stationary and non-stationary modes of external heating and electrode heating was obtained. It is shown that the effective thermal conductivity coefficient increases in proportion to the reinforcement coefficient. A significant effect of the contact layer parameters on thermal conductivity is shown, comparison with experimental data. Significant heat release in the area of contact zone and in fiber leads to a temperature rise in these zones by 20-30 degrees in a stationary mode. The temperature distribution in fiber-reinforced concrete during induction heating is considered. In this case, it is necessary to significantly increase the frequency of the current used. The study results can be used, prescribing electric heating modes for products made of dispersion-reinforced concrete.

Mathematical model for the reinforced concrete with nonlinearity behaviour of bond

The article developed a mathematical model describing the deformation of reinforced concrete, taking into account its adhesion to reinforcement. The model consists of three layers: concrete, contact layer, reinforcement. The contact layer surrounding the reinforcement takes into account the complex deformation of the concrete when interacting with the profiled reinforcement. Arguments are presented for criteria that determine the transition of concrete, reinforcement and contact layer to limit states. A diagram of testing of reinforced concrete specimen has been proposed and a procedure for processing experimental data, which allow you to determine the bond parameters. Equations that bind the mechanical characteristics of the contact layer with two the bond parameters of concrete with reinforcement are obtained. The developed model was used in the numerical solution of the problem of static pull-out of reinforcement from concrete. The calculation of the finite element method showed a good correspondence with the experimental data, including during plastic deformation of the reinforcement. This shows the correctness of theoretical provisions and developed mathematical algorithms used to model the deformation of reinforced concrete.

Intact metal/metal halide van der Waals junction enables reliable memristive switching with high endurance

Organic-inorganic or inorganic metal halide materials have emerged as a promising candidate for a resistive switching material owing to its capability to achieve low operating voltage, high on/off ratio and multi-level switching. However, the high switching variation, limited endurance and poor reproducibility of the device hinder practical use of the memristors. Here, we report a universal approach to relieve the issues by using a van der Waals metal contacts (vdWC). By transferring the pre-deposited metal contact onto the active layers, an intact junction between the metal halide and contact layer is formed without unintended damage in the active layer that has been caused by a conventional physical deposition process of the metal contacts. Compared to the thermally evaporated metal contact (EVC), the vdWC did not degrade optoelectronic quality of the underlying layer to enable memristors with reduced switching variation, significantly enhanced endurance and reproducibility relative to those based on the EVC. By adopting various metal halide active layers, versatile utility of the vdWC is demonstrated. Thus, this vdWC approach can be a useful platform technology for development of high-performance and reliable memristors for future computing.

A New Delayering Application Workflow in Advanced 5nm Technology Device with Xenon Plasma Focus Ion Beam Microscopy

In semiconductor industry, planer analysis is important in many applications such as Passive Voltage Contrast (PVC) and sample preparation for nanoprobing. In order to achieve successful results on the planer surface analysis, a proper delayering technique is critical. As the thickness of metal line, via of Back-End-of Line (BEOL) and contact layer are getting thinner in advanced nodes, we observed convention hand polishing is facing major challenge in endpointing at exactly targeted layer and specific Region of Interest (ROI). In addition, Cobalt process starting from 5nm node brings additional challenges. Cobalt tends to be oxidized easily which becomes not friendly for nanoprobing. The alternative solution to produce good planar surface is to use Plasma Focus Ion Beam (PFIB) technique with patented DX gas assisted. PFIB changes the convention FA workflow and has been proven that the new workflow improves the efficiency of planar failure analysis such as PVC and nanoprobing sample preparation.