Abstract
Memristors—competitive microelectronic elements which bring together the electronic sensing and memory effects—potentially are able to respond against physical and chemical effects that ...influence their sensing capability and memory behavior. However, this young topic is still under debate and needs further attention to be highly responding to or remaining intact against physical effects, e.g., light illumination. To contribute to this scenario, using a composite of two-dimensional graphene or MoS
2
doped with meso-structures of metal/metal-oxides of Ag, Cu and Fe family, we presented scalable and printable memristors. The memristive behavior shows strong dependency upon light illumination with a high record of 10
5
ON/OFF ratio observed so far in 2-terminal systems based on two-dimensional materials or metal oxide structures. Moreover, we found that the memristors can remain stable without illumination, providing a novel approach to use these composites for developing neuromorphic computing circuits. The sensing and memristive mechanisms are explained based on the electronic properties of the materials. Our introduced materials used in the memristor devices can open new routes to achieve high sensing capability and improve memristance of the future microelectronic elements.
Abstract
In
cis
and
trans
geometrical configurations of the polyacetylene molecule, one-dimensional chain is constructed by attaching a number of identical –HC=CH– units one-by-one. We attach as many ...units as required to obtain the chain of the desired length. In case of a very long polyacetylene chain, which is practically considered infinite in length, a periodic unit is defined, so that its band structure would be calculable. Then, the electronic properties and topological properties of the chain can be predicted. Since experimental synthesis of single-layer polyacetylene chain has lots of limitations, in an alternative approach, emulation of a tight-binding model is used to describe the electron transfer in polyacetylene polymer chain. In case of either synthesis or testing the polyacetylene molecule, it is necessary to improvise a one-to-one correspondence between polyacetylene polymer and topological circuit, which is introduced for the first time in the present study. To this aim, the outputs of density functional theory calculations alongside with the calculations based on the physical chemistry formalisms are used. Here, we observed that the electronic response of the circuit is topologically sustained at frequencies where the coupling was pre-determined via high precision quantum system equivalent topolectrical circuit, as an alternative classical system, to study electron transfer of
trans
-polyacetylene polymer quantum chain by the precision of one-electron.
Graphene as reinforcing filler in polyvinyl acetate resin Taghiyari, Hamid R.; Majidi, Roya; Mohseni Armaki, Seyed Majid ...
International journal of adhesion and adhesives,
March 2022, 2022-03-00, 20220301, Letnik:
113
Journal Article
Recenzirano
Odprti dostop
Graphene gel and powder were added to polyvinyl acetate (PVA) resin to investigate its potential improving effects on shear strength of the resin. Graphene flakes were synthesized based on a ...simultaneous electrochemical exfoliation/deposition procedure. Flakes were decorated in face with magnetic nanocrystals in hetero-structure. They were mixed with PVA resin at 3% content, based on the wet weight of the resin. Beech wood specimens (Fagus orientalis L.) were prepared according to ASTM D143-14. Separate sets of specimens were prepared to be first heated at 165 °C and 185 °C for 4 h. Results demonstrated significant improving effect of graphene powder on shear strength of PVA resin. Graphene gel did not improve shear strength due to dilution of resin. Density functional theory simulations indicated very low adsorption energy of either pure graphene (−0.45 eV) or Ni-doped graphene (−0.91 eV) flakes on cellulose. Therefore, the improving effect was not attributed to formation of new bonds between graphene flakes and cell-wall polymers. It was concluded that graphene powder acted as a reinforcing filler in the PVA resin matrix, significantly improving its shear strength in the un-heated beech specimens. However, as a result of thermal degradation of cell-wall polymers and the consequent decrease in mechanical properties of the wood, as well as a considerable decrease in wood wettability, failures occurred within the wood structure of the heat-treated specimens rather than within the bond line. Therefore, graphene powder could not improve the overall shear strength in the heat-treated specimens at 185 °C.
Abstract
We demonstrate a nanostructure layer made of Ni
80
Fe
20
(permalloy:Py) thin film conjugated MoS
2
nano-flakes. Layers are made based on a single-step co-deposition of Py and MoS
2
from a ...single solution where ionic Ni and Fe and MoS
2
flakes co-exist. Synthesized thin films with MoS
2
flakes show increasing coercivity and enhancement in magneto-optical Kerr effect. Ferromagnetic resonance linewidth as well as the damping parameter increaseed significantly compared to that of the Py layer due to the presence of MoS
2
. Raman spectroscopy and elemental mapping is used to show the quality of MoS
2
within the Py thin film. Our synthesis method promises new opportunities for electrochemical production of functional spintronic-based devices.
Abstract
Delafossite semiconductors have attracted substantial attention in the field of electro-optics owing to their unique properties and availability of p-type materials that are applicable for ...solar cells, photocatalysts, photodetectors (PDs) and p-type transparent conductive oxides (TCOs). The CuGaO
2
(CGO), as one of the most promising p-type delafossite materials, has appealing electrical and optical properties. In this work, we are able to synthesize CGO with different phases by adopting solid-state reaction route using sputtering followed by heat treatment at different temperatures. By examining the structural properties of CGO thin films, we found that the pure delafossite phase appears at the annealing temperature of 900 °C. While at lower temperatures, delafossite phase can be observed, but along with spinel phase. Furthermore, their structural and physical characterizations indicate an improvement of material-quality at temperatures higher than 600 °C. Thereafter, we fabricated a CGO-based ultraviolet-PD (UV-PD) with a metal–semiconductor-metal (MSM) configuration which exhibits a remarkable performance compared to the other CGO-based UV-PDs and have also investigated the effect of metal contacts on the device performance. We demonstrate that UV-PD with the employment of Cu as the electrical contact shows a Schottky behavior with a responsivity of 29 mA/W with a short response time of 1.8 and 5.9 s for rise and decay times, respectively. In contrast, the UV-PD with Ag electrode has shown an improved responsivity of about 85 mA/W with a slower rise/decay time of 12.2/12.8 s. Our work sheds light on the development of p-type delafossite semiconductor for possible optoelectronics application of the future.
The demonstration of biosensors based on the surface plasmon effect holds promise for future high-sensitive electrodeless biodetection. The combination of magnetic effects with surface plasmon waves ...brings additional freedom to improve sensitivity and signal selectivity. Stacking biosensors with two-dimensional (2-D) materials, e.g., graphene (Gr) and MoS2, can influence plasmon waves and facilitate surface physiochemical properties as additional versatility aspects. We demonstrate magnetoplasmonic biosensors through the detuning of surface plasmon oscillation modes affected by magnetic effect via the presence of the NiFe (Py) layer and different light absorbers of Gr, MoS2, and Au ultrathin layers in three stacks of Au/Py/M(MoS2, Gr, Au) trilayers. We found minimum reflection, resonance angle shift, and transverse magneto-optical Kerr effect (TMOKE) responses of all sensors in the presence of the ss-DNA monolayer. Very few changes of ∼5×10−7 in the ss-DNA's refractive index result in valuable TMOKE response. We found that the presence of three-layer Gr and two-layer MoS2 on top of the Au/Py bilayer can dramatically increase the sensitivity by nine and four times, respectively, than the conventional Au/Co/Au trilayer. Our results show the highest reported DNA sensitivity based on the coupling of light with 2-D materials in magnetoplasmonic devices.
Static and dynamic magnetic solitons play a critical role in applied nanomagnetism. Magnetic droplets, a type of non-topological dissipative soliton, can be nucleated and sustained in nanocontact ...spin-torque oscillators with perpendicular magnetic anisotropy free layers. Here, we perform a detailed experimental determination of the full droplet nucleation boundary in the current-field plane for a wide range of nanocontact sizes and demonstrate its excellent agreement with an analytical expression originating from a stability analysis. Our results reconcile recent contradicting reports of the field dependence of the droplet nucleation. Furthermore, our analytical model both highlights the relation between the fixed layer material and the droplet nucleation current magnitude, and provides an accurate method to experimentally determine the spin transfer torque asymmetry of each device.
Abstract
The interfacial Dzyaloshinskii-Moriya Interaction (iDMI) is an antisymmetric exchange interaction that is induced by the broken inversion symmetry at the interface of, e.g., a ...ferromagnet/heavy metal. Thus, the presence of iDMI is not expected in symmetrical multilayer stacks of such structures. Here, we use thermal annealing to induce the iDMI in a Py/Pt
×10
symmetrical multilayer stack. Brillouin light scattering spectroscopy is used to directly evidence the iDMI induction in the annealed sample. Structural characterizations highlight the modified crystallinity as well as a higher surface roughness of the sample after annealing. First principles electronic structure calculations demonstrate a monotonic increase of the iDMI with the interfacial disorder due to the interdiffusion of atoms, depicting the possible origin of the induced iDMI. The presented method can be used to tune the iDMI strength in symmetric multilayers, which are the integral part of racetrack memories, magnonic devices as well as spin-orbitronic elements.
The aim of this paper was to improve the fire retardancy of beech wood by graphene. Six fire properties, namely time to onset of ignition, time to onset of glowing, back-darkening time, back-holing ...time, burnt area and weight loss were measured using a newly developed apparatus with piloted ignition. A set of specimens was treated with nano-wollastonite (NW) for comparison with the results of graphene-treated specimens. Graphene and NW were mixed in a water-based paint and brushed on the front and back surface of specimens. Results demonstrated significant improving effects of graphene on times to onset of ignition and glowing. Moreover, graphene drastically decreased the burnt area. Comparison between graphene- and NW-treated specimens demonstrated the superiority of graphene in all six fire properties measured here. Fire retardancy impact of graphene was attributed to its very low reaction ability with oxygen, as well as its high and low thermal conductivity in in-plane and cross-section directions, respectively. The improved fire-retardancy properties by the addition of graphene in paint implied its effectiveness in hindering the spread of fire in buildings and structures, providing a longer timespan to extinguish a fire, and ultimately reducing the loss of life and property. Based on the improvements in fire properties achieved in graphene-treated specimens, it was concluded that graphene has a great potential to be used as a fire retardant in solid wood species.
Fundamental studies on graphene (Gr) and its real device applications have been affected by unavoidable defects and impurities which are usually present in synthesized Gr. Therefore, post treatment ...methods on Gr have been an important subject of research followed by the community. Here, we demonstrate a post-treatment of cm-sized CVD-grown graphene in a Radio Frequency-generated low-pressure plasma of methane and hydrogen to remove oxygen functional groups and heal the structural defects. The optimum plasma treatment parameters, such as pressure, plasma power, and the ratio of the gases, are optimized using in-situ optical emission spectroscopy. This way we present an optimal healing condition monitored with in situ OES. A twofold increase in the conductivity of plasma-treated Gr samples was obtained. Plasma treatment conditions give insights into the possible underlying mechanisms, and the method presents an effective way to obtain improved Gr quality.
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