Switching Ratio Research Articles

The annealing temperature dependence of the RRAM effect and the oxygen vacancy mechanism for double perovskite Bi2FeCrO6 film

Resistive random access memory (RRAM) is the most potentially nonvolatile memory of the next generation. In this paper, the double perovskite Bi2FeCrO6 (BFCO) thin films were prepared on FTO/glass using the sol-gel method. And, the resistive switching (RS) phenomena were observed in the Au/BFCO/FTO/glass device annealed at different temperatures. Moreover, the RS behaviors and the mechanism of the Au/BFCO/FTO device were analyzed and discussed, and the RS behaviors could be due to the interaction between the interfacial barrier and oxygen vacancies, and the change of RRAM performance under the annealing temperatures can be attributed to the crystallinity and oxygen vacancy defect content in double perovskite BFCO films, so that, the largest and most stable switching ratios of more than 102 for the BFCO film is achieved annealed at 700 °C. These findings will help us design and fabricate the multiferroic BFCO-based resistive switching memory devices.

Unparalleled Dielectric‐Switching Effects Caused by Dual Polarization Synergy

AbstractDielectric switching materials are prospective candidates for smart electronic/electrical applications, and high dielectric switching ratios are crucial for their practical applications. However, the substantial improvement of the dielectric switching ratio is limited by the available dielectric switching mechanisms, and obtaining high dielectric switching ratios is a major challenge. Here, an unparalleled dielectric switching effect is reported in a water‐in‐oil emulsion system, caused by dual polarization synergy below the dielectric transition temperature in concert with suppression of the electrode polarization above the dielectric transition temperature. The synergistic dielectric switching effect of interfacial polarization and electrode polarization endows the emulsion with unprecedentedly high dielectric switching ratios. The highest room temperature dielectric switching ratio of this emulsion system up to 2.86 × 106 at 20 Hz, is four orders of magnitude higher than the highest switching ratio reported so far. The unparalleled high dielectric switching ratio, reliable cycle stability, good frequency adaptability, and satisfactory scalability make the inorganic salt solution/octadecane emulsions potentially excellent candidates for high‐sensitivity room‐temperature smart switching or sensing devices.

Controlling the resistive switching polarity in ReS2 lateral memristors through the modulation of crystal structures

Memristors are excellent candidates for non-volatile memory and neuromorphic computing. Controlling the resistive switching polarity in certain materials holds great promise for the design and integration of multifunctional memristors. Here, bipolar and unipolar nonvolatility were realized by modulating the crystal structures, which exhibit high switching ratios, desirable cyclability, and long retention. By investigating the defect level and conductivity difference in single-crystal and polycrystal ReS2, the competition between electric field and Joule heat effects were revealed as the essential mechanism governing the switching process and memristive polarities. These results promote the design of two-dimensional memristors with controllable polarity.

Performance Assessment of a Junctionless Heterostructure Tunnel FET Biosensor Using Dual Material Gate

Biosensors based on tunnel FET for label-free detection in which a nanogap is introduced under gate electrode to electrically sense the characteristics of biomolecules, have been studied widely in recent years. In this paper, a new type of heterostructure junctionless tunnel FET biosensor with an embedded nanogap is proposed, in which the control gate consists of two parts, namely the tunnel gate and auxiliary gate, with different work functions; and the detection sensitivity of different biomolecules can be controlled and adjusted by the two gates. Further, a polar gate is introduced above the source region, and a P+ source is formed by the charge plasma concept by selecting appropriate work functions for the polar gate. The variation of sensitivity with different control gate and polar gate work functions is explored. Neutral and charged biomolecules are considered to simulate device-level gate effects, and the influence of different dielectric constants on sensitivity is also researched. The simulation results show that the switch ratio of the proposed biosensor can reach 109, the maximum current sensitivity is 6.91 × 102, and the maximum sensitivity of the average subthreshold swing (SS) is 0.62.

Sensitivity assessment of dielectric modulated GaN material based SOI-FinFET for label-free biosensing applications

Abstract This work presents the sensitivity assessment of gallium nitride (GaN) material-based silicon-on-insulator fin field effect transistor by dielectric modulation in the nanocavity gap for label-free biosensing applications. The significant deflection is observed on the electrical characteristics such as drain current, transconductance, surface potential, energy band profile, electric field, sub-threshold slope, and threshold voltage in the presence of biomolecules owing to GaN material. Further, the device sensitivity is evaluated to identify the effectiveness of the proposed biosensor and its capability to detect the biomolecules with high precision or accuracy. The higher sensitivity is observed for Gelatin (k = 12) in terms of on-current, threshold voltage, and switching ratio by 104.88%, 82.12%, and 119.73%, respectively. This work is performed using a powerful tool, three-dimensional (3D) Sentaurus Technology computer-aided design using a well-calibrated structure. The results pave the way for GaN-SOI-FinFET to be a viable candidate for label-free dielectric modulated biosensor applications.

Gate electrode work function engineered JAM-GS-GAA FinFET for analog/RF applications: Performance estimation and optimization

In this study, the gate electrode work function engineered Junctionless Accumulation Mode Gate Stack Gate All Around (JAM-GS-GAA) FinFET has been rigorously investigated for analog/RF applications. The simulated findings show that decreasing the gate electrode work function by 0.4 eV improves the static characteristics such as electric field (46.68%), electron mobility (55.0%), potential (5.74%), and electron concentration (2.97%). A 0.4 eV escalation in the gate electrode work function improves the analog parameters of the JAM-GS-GAA FinFET significantly in terms of leakage current (Ioff) (104 times), subthreshold swing (SS) (20.26%), switching ratio (Ion/Ioff) (102 to 106), and quality factor (QF) (25.54%), intrinsic gain (Av) (280.73%), early voltage (VEA) (62.12%), and output conductance (gd) (90.52%). The RF parameters follow the same trend as analog parameters. GFP and GTFP increased more than eight and ten times, respectively, with a surge in the gate electrode work function. Consequently, the findings of this research can assist engineers in designing nanoelectronic devices that meet their requirements.

Thickness-dependent microstructure, resistive switching, ferroelectric, and energy storage properties of pulsed laser deposited 0.85[0.6Ba(Zr0.2Ti0.8)O3-0.4(Ba0.7Ca0.3)TiO3]-0.15SrTiO3 thin films

In this work, we have studied the effect of thickness on structural, morphological, resistive switching (RS), ferroelectric, and energy storage properties of 0.85[0.6Ba (Zr0.2Ti0.8)O3-0.4(Ba0.7Ca0.3)TiO3]-0.15SrTiO3 (BZCT-STO) thin films deposited by the pulsed laser deposition technique. X-ray diffraction (XRD) analysis suggests that BZCT-STO thin films exhibit a polycrystalline tetragonal structure. The lattice parameters and tetragonality ratio approaching to bulk value with an increase of thickness, confirm strain relaxation in thicker films. SEM analysis reveals a dense columnar structure with a different grain size that varies from 3 nm to 60 nm as thickness increased from 160 to 360 nm. The P-E loops suggest that the relaxor behaviour increases with a decrease of thickness due to interface low dielectric layer, substrate clamping effect, small grain size, and high back switching ratio. The RS effect observed in Pt/BZCT-STO/Au capacitors is attributed to polarization modulation of the Schottky barrier and is found to be significant at low thickness. The effect of electric field and frequency on energy storage properties of BZCT-STO films is also investigated. The Pt/BZCT-STO/Au capacitor with a thickness of 160 nm exhibited 6.0 J/cm3 with an efficiency of 72% at a field of 800 kV/cm. It also exhibited a robust energy storage performance in the frequency range of 50–2000 Hz and also up to 108 cycles passing through the capacitor.

Laser‐Printed Terahertz Plasmonic Phase‐Change Metasurfaces

AbstractChalcogenide phase‐change materials (PCMs) have offered an appealing material solution by acting as a switchable dielectric layer to tune the electromagnetic properties of terahertz metamaterials and metasurfaces. Here, this work demonstrates large‐scale and lithography‐free manufacturing of all‐PCM terahertz metasurfaces based on direct laser switching of crystalline micro‐domains in a thin film with high switching ratio of the emerging plasmonic PCM, In3SbTe2 (IST). The fabricated high‐quality IST metasurfaces achieve efficient plasmonic resonances and a large modulation depth with ultrafast response (full width at half maxima of the modulation time ≈1.6 ps) in a deep‐subwavelength switching volume. For the dynamic evolution of terahertz resonance modes, theoretical modeling reveals a delicate interplay between amorphous and crystalline IST due to the bonding‐structure‐induced different carrier lifetimes and spatially localized electric fields. These studies open new avenues for realizing all‐PCM terahertz ultrafast nanophotonics.

Optoelectronic Synaptic Memtransistor Based on 2D SnSe/MoS2 van der Waals Heterostructure under UV-Ozone Treatment.

Memristive switching devices with electrically and optically invoked synaptic behaviors show great promise in constructing an artificial biological visual system. Through rational design and integration, 2D materials and their van der Waals (vdW) heterostructures can be applied to realize multifunctional optoelectronic devices. Here, a multifunctional optoelectronic synaptic memtransistor based on a SnSe/MoS2 vdW p-n heterojunction to simulate the human biological visual system is reported. By employing simple mild UV-ozone treatment, the device exhibits reversible resistive switching (RS) behavior with switching ratio up to 103 . The retina-like selective response to different input light wavelengths is activated, as well as programmable multilevel resistance states and long-term synaptic plasticity. Moreover, memory and logic functions analogous to those found in the visual cortex of the brain are performed by controlling the optical and electrical input signals. This work proposes a feasible strategy to modulate RS in vdW heterostructures for memristive devices, which show significant potential for neuromorphic processing.

Realizing Electronic Synapses by Defect Engineering in Polycrystalline Two-Dimensional MoS2 for Neuromorphic Computing.

Neuromorphic computing based on two-dimensional transition-metal dichalcogenides (2D TMDs) has attracted significant attention recently due to their extraordinary properties generated by the atomic-thick layered structure. This study presents sulfur-defect-assisted MoS2 artificial synaptic devices fabricated by a simple sputtering process, followed by a precise sulfur (S) vacancy-engineering process. While the as-sputtered MoS2 film does not show synaptic behavior, the S vacancy-controlled MoS2 film exhibits excellent synapse with remarkable nonvolatile memory characteristics such as a high switching ratio (∼103), a large memory window, and long retention time (∼104 s) in addition to synaptic functions such as paired-pulse facilitation (PPF) and long-term potentiation (LTP)/depression (LTD). The synaptic device working mechanism of Schottky barrier height modulation by redistributing S vacancies was systemically analyzed by electrical, physical, and microscopy characterizations. The presented MoS2 synaptic device, based on the precise defect engineering of sputtered MoS2, is a facile, low-cost, complementary metal-oxide semiconductor (CMOS)-compatible, and scalable method and provides a procedural guideline for the design of practical 2D TMD-based neuromorphic computing.

Multi‐Operating Mode Field‐Effect Transistors Based on SnO/SnS Heterostructures and CMOS‐Like Inverter Applications

AbstractA novel SnO/SnS heterojunction grown by pulsed laser deposition for the fabrication of high‐performance transistors with changeable polarity is described in this study. It is worth noting that the operating mode of a vertical heterojunction transistor can be switched from p‐type to ambipolar to n‐type by growing SnS with a different thickness on SnO with ambipolarity. The p‐type mobility could reach 1.77 cm2 V−1 s−1 and the switching ratio could reach 1517. The ambipolar transistor shows a V‐type transfer curve with electron channel mobility and hole mobility, respectively. The cross‐sectional transmission electron microscopy of the heterojunction interface reveals a high level of quality, which explains the method by which the working mode of the heterojunction changes. In addition, complementary metal‐oxide‐semiconductor (CMOS) inverters are successfully used with p‐type SnO transistors, n‐type SnO/SnS transistors, and ambipolar transistors. This work proposes a novel approach to preparing CMOS electrical components, as well as a new working mode for transistors, that are both simple and efficient.

Experimental and First‐Principles Study of Visible Light Responsive Memristor Based on CuAlAgCr/TiO2/W Structure for Artificial Synapses with Visual Perception

AbstractThe development of vision bionic systems is indispensable for the perception, memory, and processing of optical signals, which promotes the exploration of efficient visual perception systems. In this work, a simple and novel two‐terminal optoelectronic memristor based on the CuAlAgCr/TiO2/W (CTW) structure is prepared, where the CuAlAgCr high‐entropy alloys are employed as the top electrode for the first time. Before annealing, the CTW optoelectronic memristor exhibited fascinating performance, including uniformly distributed operating voltage, reliable data retention, and a higher switching ratio. Moreover, the optoelectronic memristor can be reversibly switched between volatile and nonvolatile memories by adjusting compliance currents. The CTW optoelectronic memristor annealed in air exhibits various artificial synaptic functions, such as short‐term memory, optical learning, and forgetting behavior under the illumination of the laser. The photo‐response current is increased from nano‐ampere to micro‐ampere level. Furthermore, a logic function unit based on CTW optoelectronic memristor is proposed, which realizes “AND” operation. Furthermore, first‐principles calculations of the CTW structure are performed to describe the influence of photocarriers on the barrier height at the CuAlAgCr‐TiO2 interface, revealing the working mechanism of the CTW optoelectronic memristor. This work has greatly facilitated the development of optically operated artificial synaptic devices and vision bionic systems.

Synaptic MoS2 transistors based on charge trapping two-dimensionally confined in Sr2-xCoxNb3O10 nanosheets

Two-dimensional (2D) synaptic devices based on charge trap/de-trap have attracted much attention due to their superior characteristics that is gate tunability, large switching ratio, long-term retention, and distinct synaptic potentiation/depression with low power. Here, we introduce a 2D Sr2-xCoxNb3O10 (SCNO) nanosheet layer between the MoS2 channel and SiO2 substrate because charge trap sites confined in SCNO nanosheet layer are anticipated to precisely control the 2D channel conductance. The hysteretic and synaptic behaviors of MoS2 channel can be controlled by charge trap/de-trap in two-dimensionally confined nanosheet layer with different doping ratio of Co. As the x value for the MoS2/SCNO field effect transistor (FET) increases, the shift of the threshold voltage (Vth) in a transfer curve increases and more linear potentiation/depression curves are induced with lower gate voltage pulse. In addition, paired-pulse facilitation is successfully implemented in a MoS2/SCNO FET. Therefore, our results suggest the feasibility of improved and efficient emulation of biological synaptic behavior in MoS2 transistors in contact with 2D oxide nanosheet layer.

Investigation on RF/Analog Performance in SiGe Pocket n-Tunnel FET

In this paper, a SiGe pocket n-TFET is designed and its electrical performance is extracted using a TCAD simulator. Initially, a comparative study of input characteristics among conventional TFET (Device 1), intrinsic SiGe pocket TFET (Device 2), and doped SiGe pocket TFET (Device 3) is presented. It is seen that Device 2 shows an improved switching ratio (ION/IOFF) compared to other Devices. Furthermore, the RF/analog performance such as transconductance (gm), output conductance (gd), intrinsic gain (gm/gd), gate capacitance (Cgg), cut-off frequency (fc), transconductance frequency product (TFP), gain frequency product (GFP), and gain transconductance frequency product (GTFP) is reported for the variation in x of SiGe pocket from 0 to 1. The eBTBT rate and electron density are plotted for the variation in x of SiGe pocket Vertical TFET. The results reveal that the increase in x leads to an improvement in RF/analog performance and the tunneling rate in SiGe pocket Vertical TFET.

Numerical simulation of Transparent Gate Thin-Film Transistor (TG-TFT) with varied gate materials for high-performance applications

This work presents the performance evaluation of Transparent Gate Thin-Film Transistor (TG-TFT) with the relative analysis of numerous materials such as Aluminum (Al), Gold (Au), Indium Tin Oxide (ITO), Zinc Oxide (ZnO), and Titanium Nitride (TiN). This work also aims to find the best suitable gate material on the TFT for high-performance applications through a solid thin film. It is observed from the outcomes that TG-TFT performance improves significantly with TiN gate in terms of mobility (∼4 times), switching ratio (ION/IOFF) by 46.42 %, and electric field by ∼ 29 % as compared to conventional gate material (Au). Further, surface potential and energy band profile have been shown. Therefore, the examination shows the perspective of TiN as gate materials that can be reused for requests in nanoelectronics tools and designing of IC boards owing to the better conductivity, robustness, and cheap nature of TiN along with proven results it can be used as a gate material.

Improvement of extinction in optically-controlled silicon thermo-optic switch based on micro-ring resonator with distinct probe signal

Herein, an optically-controlled thermo-optic switch based on a micro-ring resonator is proposed and demonstrated. The latter converts pump light to heat using a metal layer close to the waveguides to generate a phase shift based on the thermo-optic effect, thereby realizing the switching operation. By using the probe and pump lights of the transverse electric and transverse magnetic modes, respectively, optical absorption is properly designed and an extinction ratio higher than that reported in the previous study is achieved. Further, 10%–90% switching times are measured to be 0.71 μs and 2.66 μs for the rising time and cooling time of temporal response, respectively. The burst-switching measurements reveal an on/off switching ratio of 7.3 dB at the through-port and 7.2 dB at the drop port, with a pump power of 16.8 mW.

Magnetic field control and swift heavy ion beam assisted tuning of resistive switching properties of BSFO/CFO/LNO heterostructures

Resistive switching (RS) behavior in mixed oxide insulators has shown a great promise as memristors or non-volatile resistive random-access memory (RRAM) applications. For dilute magnetic oxide multilayers, a novel approach of controlled defects induced and the magnetic field control of RS behavior is proposed. Resistive switching in Bi0.6Sr0.4FeO3 /CoFe2O4 /LaNiO3 (BSFO/CFO/LNO) multilayer heterostructures has been investigated as a case study. All oxide junctions consisting of conducting LaNiO3 (LNO) bottom electrode and BSFO-CFO active layers were fabricated by using chemical solution deposition. A set of samples were irradiated with 150 MeV Ag11+ ions for three different ion fluence of ∼1 × 10+11 ions cm−2, 1 × 10+12 ions cm−2 and 5 × 10+12 ions cm−2. Polycrystalline phase pure films with smooth, crack free surfaces were observed for pristine and irradiated samples. Optical spectroscopy revealed a decrease in the transmittance upon increasing ion fluence due to increase in the light scattering centres. The optical band gap showed a systematic decrease from 2.09 eV to 1.65 eV with increasing ion fluence. Room temperature I-V characteristics showed consistent and pronounced bipolar switching for all samples below ± 5 V. Upon applied magnetic fields of 0.58 T, the resistive switching ratios were found to increase significantly and were further tuned by 150 MeV Ag11+ ion beam irradiations. The magnetic field control of electrical transport properties in the controlled defect assisted oxide heterojunctions offers new insights to the existing understanding of oxide-based RS mechanism.

Implementation and performance analysis of QPSK system using pocket double gate asymmetric JLTFET for satellite communications

This work is intended to design a quadrature phase shift keying (QPSK) system starting from the device design, characterization and optimization which is then followed by the circuit level implementation and finally the system level configuration. Tunnel Field Effect Transistor (TFET) technology came into existence because of the inability of CMOS (Complementary Metal Oxide Semiconductor) to produce reduced leakage current (Ioff) in the subthreshold regime. With the effects of scaling and requirement of high doping concentrations, TFET is not capable to produce stable reduction in Ioff due to the variation in ON and OFF current. To improve the switching ratio of the current and to obtain good subthreshold swing (SS) by overcoming the limitations of junction TFET, a new device design is proposed for the first time in this work. A pocket double gate asymmetric Junction less TFET (poc-DG-AJLTFET) structure has been proposed in which uniform doping is used to eliminate the junctions and a pocket of length 2 nm made of Silicon–Germanium (SiGe) material has been introduced to improve the designed structure performance in the weak inversion region and increase the drive current (ION). The work function has been tuned to produce the best results for poc-DG-AJLTFET and with our proposed poc-DG-AJLTFET, effects of interface traps are eliminated as against conventional JLTFET structures. The notion that low-threshold voltage device yields high IOFF has been proved wrong with our poc-DG-AJLTFET design, as it produced low threshold voltage with lower IOFF which reduced the power dissipation. Numerical results show that drain induced barrier lowering (DIBL) of 2.75 mV/V is achieved which could be less than 35 times required for short channel effects to be minimum. In terms of gate to drain capacitance (Cgd), it is found that ~ 103 reduction which greatly improves device inertia to internal electrical interference. Also, improvement in transconductance is achieved by 104 times, 103 times improvement in ION/IOFF ratio, and 400 times higher unity gain cutoff-frequency (ft) which would be required by all communication systems. The Verilog models of the designed device are used to construct the leaf cells of quadrature phase shift keying (QPSK) system and the implemented QPSK system is taken as a key evaluator in the performance evaluation in terms of propagation delay and power consumption of poc-DG-AJLTFET in modern satellite communication systems.

Current-induced switching of photonic spin Hall effect in a magnetic insulator based on spin–orbit torques

The photonic spin Hall effect (PSHE) is analogous to the electronic spin Hall effect, which has substantial potential for optoelectronic applications. However, PSHE-based devices are rarely studied, and manipulating the PSHE by charge current has remained elusive thus far. In this paper, we demonstrate current-induced switching of PSHE in the Ce1Dy2Al0.42Fe4.58O12 thin film capping with Pt electrodes, which is mediated by spin–orbit torques at the Pt/Ce1Dy2Al0.42Fe4.58O12 interface. The results show that the transverse beam shifts related to the PSHE can be reversed by applying a small order of magnitude charge current (∼108 A·m−2) to the Pt layer in opposite directions, which predicts low dissipation in our proposed heterostructure. In addition, by applying an in-plane magnetic field, the saturation beam shifts can be increased, which can significantly enhance the switching ratio.

High endurance (>1012) via optimized polarization switching ratio for Hf0.5Zr0.5O2-based FeRAM

The endurance degradation of HfO2-based ferroelectric films limits their development toward practical applications. In this work, we systematically investigate the ferroelectric endurance properties of Hf0.5Zr0.5O2 (HZO) film under various pulse voltages and pulse widths, and it is found that the fatigue severity increases first and then decreases with increasing pulse voltage or width. The nonmonotonic fatigue trend explains the controversial results in the literature that both faster and slower fatigues with increasing voltage were observed in HZO. Accordingly, low voltages of ±1.6 V/100 ns are applied for cycling the HZO device to achieve weaker fatigue and a sufficiently switched ferroelectric polarization (7–12 μC cm−2), and a recovery method by introducing wake-up effect is utilized to realize an enhanced endurance >1.01 × 1012 (>5.0 × 1013 in expectation). Our work provides a universal way to weaken fatigue and improve endurance performance of HfO2-based ferroelectric random access memory devices.