Search

Abstract Since two‐dimensionalal (2D) materials have distinct chemical and physical properties, they are widely used in various sectors of modern technologies. In the domain of diagnostic biodevices, particularly for point‐of‐care (PoC) biomedical diagnostics, 2D‐based field‐effect transistor biosensors (bio‐FETs) demonstrate substantial potential. Here, in this review article, the operational mechanisms and detection capabilities of biosensing devices utilizing graphene, transition metal dichalcogenides (TMDCs), black phosphorus, and other 2D materials are addressed in detail. The incorporation of these materials into FET‐based biosensors offers significant advantages, including low detection limits (LOD), real‐time monitoring, label‐free diagnosis, and exceptional selectivity. The review also highlights the diverse applications of these biosensors, ranging from conventional to wearable devices, underscoring the versatility of 2D material‐based FET devices. Additionally, the review provides a comprehensive assessment of the limitations and challenges faced by these devices, along with insights into future prospects and advancements. Notably, a detailed comparison of FET‐based biosensors is tabulated along with various other biosensing platforms and their working mechanisms. Ultimately, this review aims to stimulate further research and innovation in this field while educating the scientific community about the latest advancements in 2D materials‐based biosensors.

Abstract The exclusive features of two‐dimensional (2D) semiconductors, such as high surface‐to‐volume ratios, tunable electronic properties, and biocompatibility, provide promising opportunities for developing highly sensitive biosensors. However, developing practical biosensors that can promptly detect low concentrations of target analytes remains a challenging task. Here, a field‐effect‐transistor comprising n‐type transition metal dichalcogenide tin disulfide (SnS2) is developed over the hexagonal boron nitride (h‐BN) for the detection of streptavidin protein (Strep.) as a target analyte. A self‐designed receptor based on the pyrene‐lysine conjugated with biotin (PLCB) is utilized to maintain the sensitivity of the SnS2/h‐BN FET because of the π–π stacking. The detection capabilities of SnS2/h‐BN FET are investigated using both Raman spectroscopy and electrical characterizations. The real‐time electrical measurements exhibit that the SnS2/h‐BN FET is capable of detecting streptavidin at a remarkably low concentration of 0.5 pm, within 13.2 s. Additionally, the selectivity of the device is investigated by measuring its response against a Cow‐like serum egg white protein (BSA), having a comparative molecular weight to that of the streptavidin. These results indicate a high sensitivity and rapid response of SnS2/h‐BN biosensor against the selective proteins, which can have significant implications in several fields including point‐of‐care diagnostics, drug discovery, and environmental monitoring.

In this paper, we reported the cerium (Ce) doped thermoelectric materials with composition Bi2−xRxTe3 (R = Ce, x = 0.0, 0.1, and 0.2), which were prepared by using different wet chemical methods. The selected synthesis methods that were used included a simplified sol-gel method (Without Water and Surfactants-WOWS) and the Composite Mediated Hydrothermal Method (CMHM). The structural analysis of the samples showed rhombohedral and hexagonal structures. In addition, the surface morphology revealed a flower-like structure for the synthesized samples. The thermal stability was determined using differential scanning calorimetry and thermogravimetric analysis. The electrical conductivity of the samples with a doping ratio of x = 0.1 showed maximum conductivity of (19.10 × 103 (S/cm))-WOWS; (9.10 × 103 (S/cm)) – (CMHM) as compared to than that of other samples (x = 0.0 and 0.2). Interestingly, the doping of Ce increased the Seebeck effect, which also increased the power factor. The power factor of the samples x = 0.1 was higher than that of the undoped samples, which had a magnitude of 12.30 μW/cm.K2 (WOWS) and 7.02 μW/cm.K2 (CMHM). Moreover, we measured the thermal conductivity of the samples using the Advantageous Transient Plane Source (ATPS) method. Therefore, we found the higher figure of merit (ZT) value (0.41) at x = 0.1, which was prepared using a simplified sol-gel method, which is among the highest values that was reported for Bi2−xRxTe3 at room temperature. Because of its potential applications this material has great interest as a thermoelectric material and chip cooling sensing.

Abstract To avoid the complexity of the circuit for in‐memory computing, simultaneous execution of multiple logic gates (OR, AND, NOR, and NAND) and memory behavior are demonstrated in a single device of oxygen plasma‐treated gallium selenide (GaSe) memtransistor. Resistive switching behavior with RON/ROFF ratio in the range of 104 to 106 is obtained depending on the channel length (150 to 1600 nm). Oxygen plasma treatment on GaSe film created shallow and deep‐level defect states, which exhibit carriers trapping/de‐trapping, that lead to negative and positive photoconductance at positive and negative gate voltages, respectively. This distinguishing feature of gate‐dependent transition of negative to positive photoconductance encourages the execution of four logic gates in the single memory device, which is elusive in conventional memtransistor. Additionally, it is feasible to reversibly switch between two logic gates by just adjusting the gate voltages, e.g., NAND/NOR and AND/NAND. All logic gates presented high stability. Additionally, memtransistor array (1×8) is fabricated and programmed into binary bits representing ASCII (American Standard Code for Information Interchange) code for the uppercase letter “N”. This facile device configuration can provide the functionality of both logic and memory devices for emerging neuromorphic computing.

Photosensitive polyimides (PSPIs) have been widely developed in microelectronics, which is due to their excellent thermal properties and reasonable dielectric properties and can be directly patterned to simplify the processing steps. In this study, 3 μm~7 μm thick PSPI films were deposited on different substrates, including Si, 50 nm SiN, 50 nm SiO2, 100 nm Cu, and 100 nm Al, for the optimization of the process of integration with Cu films. In situ temperature-dependent resistance measurements were conducted by using a four-point probe system to study the changes in resistance of the 70 nm thick Cu films on different dielectrics with thick diffusion films of 30 nm Mn, Co, and W films in a N2 ambient. The lowest possible change in thickness due to annealing at the higher temperature ranges of 325 °C to 375 °C is displayed, which suggests the high stability of PSPI. The PSPI films show good adhesion with each Cu diffusion barrier up to 350 °C, and we believe that this will be helpful for new packaging applications, such as a 3D IC with a Cu interconnect.

The surface passivation of a CMOS image sensor (CIS) is highly beneficial for the overall improvement of a device performance. We employed the thermal atomic layer deposition (T-ALD) and plasma enhanced (PE-ALD) techniques for the deposition of 20 nm HfO2 as well as stacked with 3 and 5 nm Al2O3 thin films. The HfO2/Si and Al2O3/HfO2/Si metal-oxide-semiconductor structures were used to analyze the fixed charge density ( $\text{Q}_{\mathrm {f}}$ ) and interface trap density ( $\text{D}_{\mathrm {it}}$ ). The as-synthesized samples show high $\text{D}_{\mathrm {it}}$ and $\text{Q}_{\mathrm {f}}$ values (1012 cm−2eV−1) and a minority carrier lifetime of 15–300 $\mu \text{s}$ . The finite-difference time-domain simulation of high-k dielectrics confirmed that the Al2O3 (top)/HfO2 stacked structures expected higher quantum efficiency for CIS application. The effect of vacuum annealing (VA) and forming gas annealing (FGA) treatments succeeded with the decomposition of the $\text{D}_{\mathrm {it}}$ and increase in carrier lifetime. The H2 ambient FGA samples showed a remarkable decrease in the $\text{D}_{\mathrm {it}}$ values. To improve the overall performance of the device after passivation, we employed an Al2O3/HfO2 bilayer structure, which showed a low $\text{D}_{\mathrm {it}}$ of 1011 cm−2eV−1 and a minority carrier lifetime of $\sim 3$ ,700 $\mu \text{s}$ after 400 °C and 30 min FGA. We believe that this surface passivation strategy will pave way for future CIS technology regarding the development of lower defective surface and superior performance.

Abstract Van der Waals (vdW) heterostructures composed of atomically thin two‐dimensional (2D) materials have more potential than conventional metal‐oxide semiconductors because of their tunable bandgaps, and sensitivities. The remarkable features of these amazing vdW heterostructures are leading to multi‐functional logic devices, atomically thin photodetectors, and negative differential resistance (NDR) Esaki diodes. Here, an atomically thin vdW stacking composed of p‐type black arsenic (b‐As) and n‐type tin disulfide (n‐SnS2) to build a type‐III (broken gap) heterojunction is introduced, leading to a negative differential resistance device. Charge transport through the NDR device is investigated under electrostatic gating to achieve a high peak‐to‐valley current ratio (PVCR), which improved from 2.8 to 4.6 when the temperature is lowered from 300 to 100 K. At various applied‐biasing voltages, all conceivable tunneling mechanisms that regulate charge transport are elucidated. Furthermore, the real‐time response of the NDR device is investigated at various streptavidin concentrations down to 1 pm, operating at a low biasing voltage. Such applications of NDR devices may lead to the development of cutting‐edge electrical devices operating at low power that may be employed as biosensors to detect a variety of target DNA (e.g., ct‐DNA) and protein (e.g., the spike protein associated with COVID‐19).

Abstract Transparent and flexible diodes could be useful for future transparent electronics. Here such diodes are discussed with electrical breakdown (EBR) comprises of W/ZnO/ITO structure on the polyethylene terephthalate substrates. The three‐layered structure shows rectifying characteristics with low breakdown voltage originated from the Schottky barrier at the W/ZnO (0.8 eV) and the ZnO/ITO (0.1 eV) interfaces. Mechanical endurance is retained after different bending strengths and the rectification ratio is showed stability for 104 cycles without any significant degradation. Steep slope transistors are designed by implementing such diodes in series with the conventional field effect transistors. Such diode plus transistor stack enables field effect transistors with steep subthreshold swing of

Abstract Two-dimensional (2D) layered materials have an atomically thin and flat nature which makes it an ultimate candidate for spintronic devices. The spin-valve junctions (SVJs), composed of 2D materials, have been recognized as unique features of spin transport polarization. However, the magnetotransport properties of SVJs are highly influenced by the type of intervening layer (spacer) inserted between the ferromagnetic materials (FMs). In this situation, the spin filtering effect at the interfaces plays a critical role in the observation of the magnetoresistance (MR) of such magnetic structures, which can be improved by using promising hybrid structure. Here, we report MR of bilayer graphene (BLG), single-layer MoSe2 (SL-MoSe2), and BLG/SL-MoSe2 heterostack SVJs. However, before annealing, BLG and SL-MoSe2 SVJs demonstrate positive MR, but after annealing, BLG reverses its polarity while the SL-MoSe2 maintains its polarity and demonstrated stable positive spin polarizations at both interfaces due to meager doping effect of ferromagnetic (FM) contacts. Further, Co/BLG/SL-MoSe2/NiFe determines positive MR, i.e., ~ 1.71% and ~ 1.86% at T = 4 K before and after annealing, respectively. On the contrary, NiFe/BLG/SL-MoSe2/Co SVJs showed positive MR before annealing and subsequently reversed its MR sign after annealing due to the proximity-induced effect of metals doping with graphene. The obtained results can be useful to comprehend the origin of polarity and the selection of non-magnetic material (spacer) for magnetotransport properties. Thus, this study established a new paragon for novel spintronic applications.

Due to its high dielectric constant ( κ ), the BaTiO _3 (BTO) thin film has significant potential as a next-generation dielectric material for metal oxide semiconductor field-effect transistors (MOSFETs). Hence, the evaluation of the BTO thin film etching process is required for such nanoscale device applications. Herein, the etching characteristics and surface properties are examined according to the crystallinity of the BTO thin film. The results demonstrate that the etching rate is low in the high-crystallinity thin film, and the surface residues are much lower than in the low-crystallinity thin film. In particular, the accelerated Cl radicals in the plasma are shown to penetrate more easily into the low-crystallinity thin film than the high-crystallinity thin film. After the etching process, the surface roughness is significantly lower in the high-crystallinity thin film than in the low-crystallinity thin film. This result is expected to provide useful information for the process design of high-performance electronic devices.

Ultra-thin two-dimensional (2D) materials have attained huge interest for biosensing applications because of their strong electrostatic coupling with target molecules such as spike proteins and DNA. One such 2D material is graphene, which is extremely thin and flexible and has a strong non-covalent interaction with the supporting constructs needed to detect biomolecules. This work aimed to develop a way to efficiently functionalize the surface of 2D material using a pyrene-based supporter construct to detect the target protein. For this purpose, high-quality, pristine graphene was grown via the chemical vapor deposition (CVD) method and transferred over the Si/SiO2 substrate for its functionalization using our engineered pyrene–lysine-based supporter construct (PLB). The construct was synthesized using the solid-phase peptide synthesis (SPPS) method and utilized to functionalize the graphene-channel-based field-effect transistor (FET) device via non-covalent π−π stacking interaction. The optimum concentration of the functionalized PLB was evaluated via atomic force microscopy (AFM), Raman spectroscopy, and real-time electrical measurements. The characterization techniques successfully provide an overview of the effect of the concentration of PLB used for functionalization. Moreover, the performance was tested and compared in terms of the percentage response of the device generated after the detection of various concentrations of the streptavidin protein. This research could be useful in determining how to functionalize any 2D material by designing a supporter construct without material degradation and owing to over-stacking or bypassing surface screening effects.

The effect of residual stress during the tungsten deposition process were investigated using metal-oxide-nitride-oxide-semiconductor (MONOS) devices. The variation of residual stress due to tungsten volume was measured under tensile and compressive stress conditions. Residual stress increased in proportion to the deposition volume. Stress influenced the Si/SiO2 interface and caused deterioration of the electrical properties, which was experimentally observed during measurements of the interface trap densities and memory windows. We confirmed that residual stress led to degradation of the cell characteristics of MONOS devices, and the absolute value of stress significantly affected these issues regardless of the polarity. From our experiments results, we can predict the degradation of cell characteristics in memory devices, and confirm the need for appropriate stress control in manufacturing process.

Herein, we synthesized the zinc oxide (ZnO) thin films (TFs) deposited on glass substrates via spray pyrolysis (SP) to prepare self-cleaning glass. Various process parameters were used to optimize photocatalytic performance. Substrates were coated at room temperature (RT) and 250 °C with a 1 mL or 2 mL ZnO solution while maintaining a distance from the spray gun to the substrate of 20 cm or 30 cm. Several characterization techniques, i.e., XRD, SEM, AFM, and UV–Vis were used to determine the structural, morphological, and optical characteristics of the prepared samples. The wettability of the samples was evaluated using contact angle measurements. As ZnO is hydrophilic in nature, the RT deposited samples showed a hydrophilic character, whereas the ZnO TFs deposited at 250 °C demonstrated a hydrophobic character. The XRD results showed a higher degree of crystallinity for samples deposited on heated substrates. Because of this higher crystallinity, the surface energy decreased, and the contact angle increased. Moreover, by using 2 mL solution, better surface coverage and roughness were obtained for the ZnO TFs. However, by exploiting the distance of the spray to the samples size distribution and surface coverage can be controlled, the samples deposited at 30 mL showed a uniform particle size distribution from 30–40 nm. In addition, the photoactivity of the samples was tested by the degradation of rhodamine B dye. Substrates prepared with a 2 mL solution sprayed at 20 cm showed higher dye degradation than other samples, which can play a vital role in self-cleaning. Hence, by changing the said parameters, the ZnO thin film properties on glass substrates were optimized for self-cleaning diversity.

Two-dimensional (2D) layered materials and their heterostructures have opened a new avenue for next-generation spintronic applications, benefited by their unique electronic properties and high crystallinity with an atomically flat surface. Here, we report magnetoresistance of vertical magnetic spin-valve devices with multi-layer (ML) MoSe2 and its heterostructures with few-layer graphene (FLG). We employed a micro-fabrication procedure to form ultraclean ferromagnetic–non-magnetic–ferromagnetic interfaces to elucidate the intrinsic spin-transferring mechanism through both an individual material and combinations of 2D layered materials. However, it is revealed that the polarity of tunneling magnetoresistance (TMR) is independent of non-magnetic spacers whether the spin valve is composed of a single material or a hybrid structure, but it strongly depends on the interfaces between ferromagnetics (FMs) and 2D materials. We observed positive spin polarizations in ML-MoSe2 and FLG/ML-MoSe2/FLG tunnel junctions, whereas spin-valve devices comprised of FLG/ML-MoSe2 showed a reversed spin polarization and demonstrated a negative TMR. Importantly, in Co/FLG/ML-MoSe2/FLG/NiFe devices, the polarization of spin carriers in the FM/FLG interface remained conserved during tunneling through MoSe2 flakes in spin-transferring events, which is understandable by Julliere’s model. In addition, large TMR values are investigated at low temperatures, whereas at high temperatures, the TMR ratios are deteriorated. Furthermore, the large values of driving ac-current also quenched the amplitude of TMR signals. Therefore, our observations suggest that the microscopic spin-transferring mechanism between ferromagnetic metals and 2D materials played a momentous role in spin-transferring phenomena in vertical magnetic spin-valve junctions.

Two-terminal, non-volatile memory devices are the fundamental building blocks of memory-storage devices to store the required information, but their lack of flexibility limits their potential for biological applications. After the discovery of two-dimensional (2D) materials, flexible memory devices are easy to build, because of their flexible nature. Here, we report on our flexible resistive-switching devices, composed of a bilayer tin-oxide/tungsten-ditelluride (SnO2/WTe2) heterostructure sandwiched between Ag (top) and Au (bottom) metal electrodes over a flexible PET substrate. The Ag/SnO2/WTe2/Au flexible devices exhibited highly stable resistive switching along with an excellent retention time. Triggering the device from a high-resistance state (HRS) to a low-resistance state (LRS) is attributed to Ag filament formation because of its diffusion. The conductive filament begins its development from the anode to the cathode, contrary to the formal electrochemical metallization theory. The bilayer structure of SnO2/WTe2 improved the endurance of the devices and reduced the switching voltage by up to 0.2 V compared to the single SnO2 stacked devices. These flexible and low-power-consumption features may lead to the construction of a wearable memory device for data-storage purposes.

NiMnSn ferromagnetic shape memory alloys exhibit martensitic transformation at low temperatures, restricting their applications. Therefore, this is a key factor in improving the martensitic transformation temperature, which is effectively carried out by proper element doping. In this research, we investigated the martensitic transformation and magnetic properties of Ni43Mn46-x SmxSn11 (x = 0, 1, 2, 3) alloys on the basis of structural and magnetic measurements. X-ray diffraction showed that the crystal structure transforms from the cubic L21 to the orthorhombic martensite and gamma (γ) phases. The reverse martensitic and martensitic transformations were indicated by exothermic and endothermic peaks in differential scanning calorimetry. The martensitic transformation temperature increased considerably with Sm doping and exceeded room temperature for Sm = 3 at. %. The Ni43Mn45SmSn11 alloy exhibited magnetostructural transformation, leading to a large magnetocaloric effect near room temperature. The existence of thermal hysteresis and the metamagnetic behavior of Ni43Mn45SmSn11 confirm the first-order magnetostructural transition. The magnetic entropy change reached 20 J·kg−1·K−1 at 266 K, and the refrigeration capacity reached ~162 J·Kg−1, for Ni43Mn45SmSn11 under a magnetic field variation of 0–5 T.

Organic nonvolatile memory devices have a vital role for the next generation of electrical memory units, due to their large scalability and low-cost fabrication techniques. Here, we show bipolar resistive switching based on an Ag/ZnO/P3HT-PCBM/ITO device in which P3HT-PCBM acts as an organic heterojunction with inorganic ZnO protective layer. The prepared memory device has consistent DC endurance (500 cycles), retention properties (104 s), high ON/OFF ratio (105), and environmental stability. The observation of bipolar resistive switching is attributed to creation and rupture of the Ag filament. In addition, our conductive bridge random access memory (CBRAM) device has adequate regulation of the current compliance leads to multilevel resistive switching of a high data density storage.

Many thin film-based devices with solid electrolytes have been studied for memristive applications. Herein, we report a simple and facile way to fabricate solution-based, low-cost, and discrete two-terminal memristive devices using the KMnO _4 solution. The water and methanol were used as a solvent to prepare different concentrations of KMnO _4 to carry out the optimization study. Furthermore, the effect of KMnO _4 concentration with aqueous and methanol solvents was studied with the help of current-voltage, device charge, charge-flux, and cyclic endurance properties. Interestingly, all developed devices show the asymmetric time-domain charge and double valued charge-flux properties, suggesting that aqueous KMnO _4 and methanol-KMnO _4 based devices are non-ideal memristors or memristive devices. The statistical measures such as cumulative probability and coefficient of variation are reported for the memristive devices. The possible switching mechanism of the discrete memristive was tried to explain with the UV-visible spectrum and theoretical framework. The optimized device was further studied using the cyclic voltammogram, Bode plot, and Nyquist plot. An equivalent circuit was derived for the optimized discrete memristive device using electrochemical impendence spectroscopy results. The results of the present investigation are beneficial to develop programmable analog circuits, volatile memory, and synaptic devices using discrete memristive devices.

The diversity of brain functions depend on the release of neurotransmitters in chemical synapses. The back gated three terminal field effect transistors (FETs) are auspicious candidates for the emulation of biological functions to recognize the proficient neuromorphic computing systems. In order to encourage the hysteresis loops, we treated the bottom side of MoTe2 flake with deep ultraviolet light in ambient conditions. Here, we modulate the short-term and long-term memory effects due to the trapping and de-trapping of electron events in few layers of a MoTe2 transistor. However, MoTe2 FETs are investigated to reveal the time constants of electron trapping/de-trapping while applying the gate-voltage pulses. Our devices exploit the hysteresis effect in the transfer curves of MoTe2 FETs to explore the excitatory/inhibitory post-synaptic currents (EPSC/IPSC), long-term potentiation (LTP), long-term depression (LTD), spike timing/amplitude-dependent plasticity (STDP/SADP), and paired pulse facilitation (PPF). Further, the time constants for potentiation and depression is found to be 0.6 and 0.9 s, respectively which seems plausible for biological synapses. In addition, the change of synaptic weight in MoTe2 conductance is found to be 41% at negative gate pulse and 38% for positive gate pulse, respectively. Our findings can provide an essential role in the advancement of smart neuromorphic electronics.

In this study, the dominant role of the top electrode is presented for Nb2O5-based devices to demonstrate either the resistive switching or threshold characteristics. These Nb2O5-based devices may exhibit different characteristics depending on the selection of electrode. The use of the inert electrode (Au) initiates resistive switching characteristics in the Au/Nb2O5/Pt device. Alternatively, threshold characteristics are induced by using reactive electrodes (W and Nb). The X-ray photoelectron spectroscopy analysis confirms the presence of oxide layers of WOy and NbOx at interfaces for W and Nb as top electrodes. However, no interface layer between the top electrode and active layer is detected in X-ray photoelectron spectroscopy for Au as the top electrode. Moreover, the dominant phase is Nb2O5 for Au and NbO2 for W and Nb. The threshold characteristics are attributed to the reduction of Nb2O5 phase to NbO2 due to the interfacial oxide layer formation between the reactive top electrode and Nb2O5. Additionally, reliability tests for both resistive switching and threshold characteristics are also performed to confirm switching stabilities.

The algorithmic spectrometry as an alternative to traditional approaches has the potential to become the next generation of infrared (IR) spectral sensing technology, which is free of physical optical filters, and only a very small number of data are required from the IR detector. A key requirement is that the detector spectral responses must be engineered to create an optimal basis that efficiently synthesizes spectral information. Light manipulation through metal perforated with a two-dimensional square array of subwavelength holes provides remarkable opportunities to harness the detector response in a way that is incorporated into the detector. Instead of previous experimental efforts mainly focusing on the change over the resonance wavelength by tuning the geometrical parameters of the plasmonic layer, we experimentally and numerically demonstrate the capability for the control over the shape of bias-tunable response spectra using a fixed plasmonic structure as well as the detector sensitivity improvement, which is enabled by the anisotropic dielectric constants of the quantum dots-in-a-well (DWELL) absorber and the presence of electric field along the growth direction. Our work will pave the way for the development of an intelligent IR detector, which is capable of direct viewing of spectral information without utilizing any intervening the spectral filters.

Infrared (IR) polarimetric imaging has attracted attention as a promising technology in many fields. Generally, superpixels consisting of linear polarizer elements at different angles plus IR imaging array are used to obtain the polarized target signature by using the detected polarization-sensitive intensities. However, the spatial arrangement of superpixels across the imaging array may lead to an incorrect polarimetric signature of a target, due to the range of angles from which the incident radiation can be collected by the detector. In this article, we demonstrate the effect of the incident angle on the polarization performance of an alternative structure where a dielectric layer is inserted between the nanoimprinted subwavelength grating layers. The well-designed spacer creates the Fabry–Perot cavity resonance, and thereby, the intensity of transverse-magnetic I-polarized light transmitted through two metal grating layers is increased as compared with a single-layer metal grating, whereas transverse-electric (TE)-transmitted light intensity is decreased. TM-transmittance and polarization extinction ratio (PER) of normally incident light of wavelength 4.5 μm are obtained with 0.49 and 132, respectively, as the performance of the stacked subwavelength gratings. The relative change of the PERs for nanoimprint-lithographically fabricated double-layer grating samples that are less than 6% at an angle of incidence up to 25°, as compared to the normal incidence. Our work can pave the way for practical and efficient polarization-sensitive elements, which are useful for many IR polarimetric imaging applications.

In this paper, we examine the performance limitations of graphene nanoribbon field effect transistors (GNRFETs) with various channel dimensions and electrode contact resistances. To do this, we formulate a self-consistent non-equilibrium Green’s function method in conjunction with the Poisson equation. We model the behavior of GNRFETs with nanometer dimensions and relatively large bandgaps operating as metal–oxide–semiconductor field effect transistors (MOSFETs) and calculate their performance including contact resistance effects typically occurring at the graphene nanoribbon (GNR) channel and electrodes. We propose a metric for GNRFETs to compete with the current silicon CMOS high performance or low power devices and explain that this can vary significantly depending on the contact resistance. [ABSTRACT FROM AUTHOR]

In this present article, we have reported a simple and cost-effective ex-situ synthesis of TiO2-ZnO (TZ) nanocomposite thin film by utilizing sol-gel, hydrothermal and solid-state reaction methods. The Ag/TZ/FTO nanocomposite device was developed and demonstrated the bipolar resistive switching (RS) characteristics for resistive memory applications. The result of XRD analysis confirms that the nanocomposite has mixed tetragonal and hexagonal crystal structures of TiO2 and ZnO, respectively. The hysteresis loop is an essential criterion for recognizing memristive devices and similar characteristic was noticed for the developed nanocomposite device. Besides, basic memristive properties were calculated from the I-V data. The charge transportation of Ag/TZ/FTO nanocomposite device takes place because of Ohmic and space charge limited current. The collective effect of oxygen vacancies and Ag ions was a basis of RS effect in the Ag/TZ/FTO nanocomposite device. [ABSTRACT FROM AUTHOR]

The Cu2O thin film was developed using an electrodeposition approach for resistive memory application. The impact of the deposition voltage (1V, 2V, 3V, and 4V) on resistive switching (RS)/memristive properties of Cu2O thin films was studied. The XRD spectrum reveals that deposited Cu2O has a cubic crystal structure. The bipolar RS in Al/Cu2O/FTO device was clearly observed during the current-voltage (I-V) measurement. The basic memristive properties were calculated from I-V data. The charge transport studies suggested that the SCLC mechanism was responsible for device conduction, and RS was due to filamentary effect. The result suggested that the electrodeposition technique is useful to fabricate a memristive device for various applications. [ABSTRACT FROM AUTHOR]

We have developed Ti6O thin film using the electrochemical anodization approach for resistive switching (RS) application. The effect of anodization time (1 h, 2 h and 3 h) on the RS/memristive properties was investigated. The structural analysis was carried out by using the XRD technique, which reveals that the formation of the sub-stoichiometric Ti6O phase. The scanning electron microscopy image reveals that the thin film has compact and porous surface morphology. The electrical results clearly show bipolar RS in Al/Ti6O/Ti device. The boost in the RS properties was achieved by increasing the anodization time. The basic memristive properties were calculated using experimental I-V data. The Schottky, Hopping and Ohmic charge transport mechanisms contribute to the conduction, whereas the filamentary effect controls the RS process of the Al/Ti6O/Ti memristive devices. [ABSTRACT FROM AUTHOR]

In the present work, the effect of reset voltage, filament radius, filament resistivity, and oxide membrane thickness on the nanoscale ZrO2 RRAM devices was reported. The present investigation is based on the thermal reaction model of RRAM. The outcomes show a decline in saturated temperature with a rise in the radius and resistivity of filament. Furthermore, increases in saturated temperature with an increase in oxide membrane thickness were observed for the ZrO2 based RRAM device. The saturated temperature of the device was mainly influenced by reset voltage, oxide layer thickness, filament size, and filament resistivity. The simulation results of the present investigation can be beneficial for the optimization of RRAM devices. [ABSTRACT FROM AUTHOR]

The majority of the research work in the area of resistive switching has been carried out with the help of organic, inorganic and hybrid materials. Only a few reports investigate resistive switching properties of ionic liquid and soft materials. In this report, we have synthesized ZnO nanorods (NRs) and Bmim(Br) ionic liquid using simple and low-temperature chemical route i.e., hydrothermal and reflux method, respectively. The structural study of ZnO NRs indicates that the formation of hexagonal crystal structure, evident from the XRD pattern. The FESEM image suggested the formation of nanorods like morphology. The effect of dispersed ZnO NRs on the resistive switching behavior of Bmim(Br) ionic liquid was studied. The study explains the change in switching behavior by dispersing the different concentrations of ZnO NRs in ionic liquid. The results demonstrated that the dispersed ZnO NRs in ionic liquid plays a vital role and will be a potential active switching material for resistive switching applications. [ABSTRACT FROM AUTHOR]

The phase transformations and microstructural changes of NiPtSi/polysilicon fuses programmed with three different current densities, such as under, optimal and over programming, are studied. The conduction paths created by the unremoved silicide in fuse link have caused the postprogramming resistance of the overprogrammed fuse to be low.

Co/Pd multilayers that allow better tailor-design of magnetization and anisotropy is considered. Micromagnetic modeling of thin magnetic multilayers films possessing perpendicular anisotropy is conducted to estimate the size dependence of magnetic properties, especially, in the submicrometer region.

Oscillations in the transient current profiles of NiOx resistive switching memory during set and reset pulse programming were observed and explained by the repeated threshold switching (instantaneous set/reset programming) due to the unstably applied voltage on the resistive random access memory cell during switching. Adding a feedback circuit to prevent the observed oscillations as well as limiting the parasitic capacitance are needed for stable unipolar resistive memory switching. [ABSTRACT FROM AUTHOR]

Electrical voltage polarity-dependent failures of Ti/TiN/W via fuses were observed and analyzed by microstructural analyses and flux calculations based on the simulated Thomson-shifted temperature profiles. In the forward program, electromigration (EM) was in the same direction as thermomigration (TM), while in the reverse program, EM was in the opposite direction from TM, which made the forward program more efficient. When designing a fuse device, various fluxes had to be taken into account. [ABSTRACT FROM AUTHOR]

The typical double-barrier magnetic tunnel junction (DMTJ) structure examined in this paper consists of a Ta 45/Ru9.5/IrMn 10/CoFe 7/AlOx/free layer/AlOx/CoFe 7/IrMn 10/Ru 60 (nm). The free layer consists of an Ni16 Fe62 Si8 B14 7 nm, Co90 Fe10 (fcc) 7 nm, or CoFe t1/NiFeSiB t2/CoFe t1 layer in which the thicknesses t1 and t2 are varied. The DMTJ with an NiFeSiB-free layer had a tunneling magnetoresistance (TMR) of 28%, an area-resistance product (RA) of 86 Ω 11 μm², a coercivity (Hc) of 11 Oe, and an interlayer coupling field (Hi) of 20 Oe. To improve the TMR ratio and RA, a DMTJ comprising an amorphous NiFeSiB layer that could partially substitute for the CoFe free layer was investigated. This hybrid DMTJ had a TMR of 30%, an RA of 68 k Ωμ m², and a Hc of 11 Oe, but an increased Hi of 37 Oe. We confirmed by atomic force microscopy and transmission electron microscopy that Hi increased as the thickness of NiFeSiB decreased. When the amorphous NiFeSiB layer was thick, it was effective in retarding the columnar growth which usually induces a wavy interface. However, if the NiFeSiB layer was thin, the roughness was increased and Hi became large because of the magnetostatic Néel coupling. [ABSTRACT FROM AUTHOR]

In magnetic nanoconstriction systems, the magnetic calculations on the domain wall width (DWW) were carried out using the micromagnetics simulation based on Landau-Lifschitz-Gilbert equation. The results for the normal constriction type and the newly designed round constriction type were compared. DWW changes in various nanoconstriction sizes and shapes were studied while domain walls were constricted at the nanoconstriction. Calculations showed that the domain wall (DW) configurations in the normal constriction type were unstable depending on the initial state, whereas the domain wall configurations were stable in the round constriction type independent of the initial state. The stable DW configuration in the round constriction type seems to be due to the same spatial gradient across the structure. [ABSTRACT FROM AUTHOR]

This study describes the design of a flexible narrowband organic photodiode (OPDs) with a novel structure. A bulk heterojunction of poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl-C70-butyric acid methyl ester (PC70BM) is introduced as a photoactive layer, with an optimized thickness of 160 nm, and a MoO3/Ag/MoO3 (MAM) multilayer electrode and polyimide (PI) film substrate were used. The OPD with the device architecture of PI/MAM/P3HT:PC70BM/Al showed narrowband photodiode performance in the 500–650 nm wavelength range. The maximum external quantum efficiency (EQE) of the OPD was 15.41% at 570 nm, which dropped to ∼0% outside the operation wavelength range. This narrowband detectivity originated from the cutoff of light at wavelengths below 500 nm by the PI substrate and photoreactivity of P3HT:PC70BM at wavelengths between 300 and 650 nm. Outer bending tests performed over 1000 cycles revealed that the average maximum EQE remained at ∼15%. The maximum responsivity of the OPD was calculated to be 0.07 A W−1 at 570 nm. The OPD device showed a narrow response spectrum with a full width at half maximum of 100 nm. This research suggests a new approach for the fabrication of flexible OPDs with high selectivity in color detection. [ABSTRACT FROM AUTHOR]

In this paper, we theoretically investigate the highest possible expected performance for graphene nanoribbon field effect transistors (GNRFETs) for a wide range of operation voltages and device structure parameters, such as the width of the graphene nanoribbon and gate length. We formulated a self-consistent, non-equilibrium Green’s function method in conjunction with the Poisson equation and modeled the operation of nanometer sized GNRFETs, of which GNR channels have finite bandgaps so that the GNRFET can operate as a switch. We propose a metric for competing with the current silicon CMOS high performance or low power devices and explain that this can vary greatly depending on the GNRFET structure parameters. [ABSTRACT FROM AUTHOR]

In previous work, the present authors discovered the resonant splitting phenomenon of a plasmonic perforated gold film (PGF), as the incident light comes in the polar angle. However, in reality, the light through the imaging lens could be incident on the PGF not only in the polar angle but also in the azimuth angle. The transmission of a PGF against the incident light is analysed in both polar and azimuth angles in spherical coordinates. To mimic the incidence through the lens, a PGF sample is rotated by simultaneously varying both types of angles as normal incidence arrives. For the measurement, the sample has been fabricated with a PGF on a semi-insulating gallium arsenide (GaAs) substrate. The measured transmission spectra show both resonant splitting and merging under TM and TE polarisations as the azimuth angle is increased. Results drawn from this work will pave the way tofully understanding the interaction between the imaging lens and the plasmonic structure (PGF). [ABSTRACT FROM AUTHOR]

The phase transformation induced resistive switching behavior of an Al/Cu2Se/Pt device was studied. While the device did not demonstrate any resistive switching behavior at room temperature, it exhibited resistive switching behavior at 125 °C, near the transition temperature of copper(I) selenide (Cu2Se) (137 °C), where Cu2Se is known to transform from the monoclinic to superionic phase. The increase in ionic conductivity and structural variations (from ordered to disordered structure) associated with phase transformation were observed to be responsible for the origin of the switching behavior and increase in the on/off resistance ratio near the transition temperature. Thermodynamic calculations showed that a reduction in Gibb’s free energy of nucleation and an increase in the migration speed of the Cu ion associated with the ionic conductivity and order to disorder the transition of the Cu2Se at the transition temperature were the important factors responsible for the reduction in the SET voltages at 155 °C. [ABSTRACT FROM AUTHOR]

The diffusion barrier property of directly grown graphene–graphite films between Al2O3 films and Si substrates was evaluated using metal–insulator–semiconductor (MIS) structures. The roughness, morphology, sheet resistance, Raman spectrum, chemical composition, and breakdown field strength of the films were investigated after rapid thermal annealing. About 2.5-nm-thick graphene–graphite films effectively blocked the formation of the interfacial layer between Al2O3 films and Si, which was confirmed by the decreased breakdown field strength of graphene–graphite film structures. After annealing at 975 °C for 90 s, the increase in the mean breakdown field strength of the structure with the ∼2.5-nm-thick graphene–graphite film was about 91% (from 8.7 to 16.6 MV/cm), while that without the graphene–graphite film was about 187% (from 11.2 to 32.1 MV/cm). Si atom diffusion into Al2O3 films was reduced by applying the carbon-based diffusion barrier. [ABSTRACT FROM AUTHOR]

The electrical characteristics and step coverage of ZrO2 films deposited by atomic layer deposition were investigated for through-silicon via (TSV) and metal–insulator–metal applications at temperatures below 300 °C. ZrO2 films were able to be conformally deposited on the scallops of 50-µm-diameter, 100-µm-deep TSV holes. The mean breakdown field of 30-nm-thick ZrO2 films on 30-nm-thick Ta(N) increased about 41% (from 2.7 to 3.8 MV/cm) upon H2 plasma treatment. With the plasma treatment, the breakdown field of the film increased and the temperature coefficient of capacitance decreased significantly, probably as a result of the decreased carbon concentration in the film. [ABSTRACT FROM AUTHOR]