Switching Speed Research Articles

High–Speed Laser Modulation for Low–Noise Micro–Cantilever Array Deflection Measurement

In this paper, an innovative approach is introduced to address the noise issues associated with micro–cantilever array deflection measurement systems employing multiple lasers. Conventional systems are affected by laser mode hopping during switching, resulting in wavelength instability and beam spot fluctuations that take several hundred milliseconds to stabilize. To mitigate these limitations, a high–speed laser modulation technique is utilized, leveraging the averaging effect over multiple modulation cycles within the sampling window. By driving the lasers with a high–frequency carrier signal, a low–noise and stable output suitable for micro–cantilever beam deflection measurement is achieved. The effectiveness of this approach is demonstrated by simultaneously modulating the lasers and rapidly observing the spectral and centroid variations during high–speed switching using a custom–built high–speed spectrometer. The centroid fluctuations are also analyzed under different modulation frequencies. The experimental results confirm that the high–speed modulation method can reduce the standard deviation of beam spot fluctuations by more than 90%, leading to significant improvements in noise reduction compared to traditional laser switching methods. The proposed high–speed laser modulation approach offers a promising solution for enhancing the precision and stability of multi–laser micro–cantilever array deflection measurement systems.

Reduction of write current with improved thermal stability in GeSe2 doped Sb2Te3 films for phase change memory applications

Chalcogenide alloy-based semiconductors have gained significant attention in recent decades due to its applications in phase change memory (PCM). Sb2Te3 has proven to be an alternative to Static and Dynamic Random Access Memory and can be a suitable candidate for commercial memory devices due to their fast switching speed. However, Sb2Te3 suffers from low amorphous phase stability and high RESET current, which needs further improvement for high power efficiency. In this work, we have prepared (Sb2Te3)1−x (GeSe2) x (x = 0.06, 0.12, 0.18, 0.24, 0.3) films to investigate their PCM properties. The films showed a rise in transition temperature to transform from high resistive amorphous (RESET) to low resistive crystalline (SET) states with doping that leads to significant enhancement in amorphous phase stability. For 30% doping of GeSe2 in Sb2Te3, the data retention temperature increases from 20.2 °C to 84.6 °C, and the resistance contrast also increases from 102 to 105. The rise in electrical resistance with doping in the amorphous as well as crystalline states leads to a drop in threshold current (I th) from 3.5 to 0.8 mA. This also reduces the RESET and SET currents. By analyzing the samples using finite element method, it was found out that the high resistance materials produce more heat, resulting in a lower write current in an energy efficient PCM device.

A universal pre-charging method for enhancing transient speed in Organic Electrochemical Transistors

Organic electrochemical transistors (OECT) have shown great potential in diverse applications; however, in many OECTs, their slow transient response has thus far limited their practical use. One reason for the slow response is the complex interplay between lateral and vertical ion transport that has so far been poorly understood. In this work, we study the impact of lateral ion transport on OECT transient response, introduce a robust pre-charging method to manipulate the slow lateral ion transport. This approach leads to quicker ion redistribution and improved switching speeds. We show the general utility of pre-charging method in enhancing the switching speeds across various material systems, characterized by both low and high ion mobilities, and across different device architectures, achieving nearly symmetric speeds for both on-switching and off-switching. Moreover, we showcase the efficacy of the pre-charging method in enabling slow OECTs to capture rapid signals in real-world applications. Our findings present a groundbreaking strategy for enhancing the response times of OECT devices and deepening our understanding of the transient mechanisms in OECT device.

Phase change material metasurface loading enables an ultrafast all-optically switchable, compact, narrowband freespace optical filter

Active metasurfaces leveraging phase change materials (PCMs) remain a subject of intense investigation, owing to their inherent tunable properties and successful integration into integrated photonics. By harnessing the ultra-compact form factor of optical metasurfaces, further advancements in switching speeds and reduction in switching energies have the potential to revolutionize applications in free space optical communication, optical signal processing, neuromorphic photonics, quantum photonics, and compact LiDAR. In this context, an ultrafast all-optically switchable narrowband spectral filter employing a distributed Bragg reflector cavity loaded with a PCM-metasurface is proposed. The work involves a comprehensive numerical exploration of its optical properties, encompassing design optimization and anticipating limits in switching speeds and energy requirements. Specifically, focusing on a GST225 metasurface operating in the shortwave-infrared spectrum, the numerical investigations reveal the potential to achieve transmission contrast levels as high as 24 dB, accompanied by Q-factors up to a thousand and less than 1 dB insertion loss. This performance notably outperforms recently reported free-standing PCM metasurfaces and cavities loaded with unstructured PCM thin films. Furthermore, the study predicts full-cycle reconfigurability (transitioning from amorphous to crystalline states and vice versa) with anticipated switching speeds of 91 & 200 MHz and switching fluence of 0.655 & 0.616 mJ/cm2 per cycle for the RESET and SET processes respectively. This investigation holds promise for advancing the state-of-the-art performance of PCM-based metasurfaces.

Impact of varying channel length on Analog/RF performances in a novel n-type silicon-based DG-JLT

Shrinking MOSFETs suffer performance hits due to short-channel effects and leakage. Junctionless transistors JLTs emerge as promising alternatives due to simpler fabrication and better gate control. This paper investigates the analog and RF performance characteristics of n-type Silicon-Based Double Gate Junctionless Transistors with varying channel lengths (15 nm, 20 nm, and 25 nm) This study evaluates analog device performance through critical parameters: drain current density (Id), transconductance (gm), output resistance (RO), intrinsic gain (gmRO), and transconductance generation factor (gm/Id). These parameters assess current handling, gain characteristics, and design efficiency, providing a comprehensive analysis for analog circuit applications. Results indicate that the device having 15 nm channel length exhibits a transconductance which is 25.38 % more than the 20 nm variant and drain current which is 44.7 % more than the latter, suggesting its superior performance to devices with longer channel lengths. In addition, the RF performance of the devices is evaluated using the small signal model of the device. This work further investigates the high-frequency response of the devices using key figures of merit (FoMs): gate capacitances (Cgs, Cgd, Cgg), cut-off frequency (fT), and maximum oscillation frequency (fMAX). These parameters quantify the influence of parasitic capacitances on switching speed and the maximum useable frequency for analog and RF applications. Analyzing Cgs, Cgd, and Cgg reveals the impact of gate control on high-frequency operation. The device having 15 nm channel length, exhibits an increase of 47.29 % in fT and 68.97 % increase in fMAX compared to device having 20 nm channel length. The findings underscore the significance of channel length optimization in enhancing the Analog and RF performance of n-type Silicon-based Double Gate Junctionless Transistors.

Electropolymerization of D-A-D type butterfly-shaped monomers based on triphenylamine-thiophene consisting of camphor substituted quinoxaline moiety for efficient electrochromism and supercapacitors

Two new butterfly-shaped monomers TTCQF and TTCQH consisting of camphor-substituted quinoxaline units as π-spacers were designed and synthesized, which were further electrochemical polymerized and deposited on ITO substrates for electrochromic energy storage devices. The present cross-linked polymer thin films PTTCQF and PTTCQH displayed prominent color changes with significant optical contrast in both the visible and near-infrared regions under external electrical stimuli. These two polymers showcased superior electrochromic performance, involving high optical contrast, fast switching speed, and good coloration efficiency. Additionally, both polymers demonstrated a high areal specific capacitance (12 mF/cm2 for PTTCQH and 9.97 mF/cm2 for PTTCQF) at a current density of 0.1 mA/cm2. Electrochromic energy storage devices based on these polymers were fabricated, and not only illuminated an LED bulb but also visually indicated the energy storage state, guaranteed their potential for applications in energy-saving smart windows. This work may provide valuable insights into the development of efficient cross-linked electrochromic energy storage polymers.

Ultrafast high-endurance memory based on sliding ferroelectrics.

The persistence of voltage-switchable collective electronic phenomena down to the atomic scale has extensive implications for area- and energy-efficient electronics, especially in emerging nonvolatile memory technology. We investigate the performance of a ferroelectric field-effect transistor (FeFET) based on sliding ferroelectricity in bilayer boron nitride at room temperature. Sliding ferroelectricity represents a different form of atomically thin two-dimensional (2D) ferroelectrics, characterized by the switching of out-of-plane polarization through interlayer sliding motion. We examined the FeFET device employing monolayer graphene as the channel layer, which demonstrated ultrafast switching speeds on the nanosecond scale and high endurance exceeding 1011 switching cycles, comparable to state-of-the-art FeFET devices. These characteristics highlight the potential of 2D sliding ferroelectrics for inspiring next-generation nonvolatile memory technology.

Physics-guided fuel-switching neural networks for stable combustion of low calorific industrial gas

Dual fuel combustion of low calorific industrial gas has been widely used in various types of burners for industrial production needs. Fuel switching rule is purely empirical lacking theoretic basis, potentially leading to flame extinction or excessive waste of ignition fuel. This study focuses on exploring physics-guided fuel-switching strategy for stable combustion of coke oven gas (COG) and blast furnace gas (BFG) in representative swirl burner. Stable operating regimes for COG and BFG are firstly identified with chemical eigen-analysis. The intrinsic propensity of flame extinction during fuel switching is revealed by positive chemical eigenvalues, and the key species and elementary reactions are identified. A clustered neural network with flag controller (CNNF) is then constructed to achieve stable combustion during fuel switching from COG to BFG as early as possible to reduce the use of COG. Results show that COG must be used to ignite and increase the ambient temperature to at least 673 K to avoid flame extinction. The chemical eigen-guided CNNF controller can adjust the switch speed to advance the fuel switching time by 14 % and can be further expanded to other fuel switching applications.

Compatible multilayer magnetic field system for quantum sensing with atoms.

Magnetic fields provide a valuable method to manipulate atomic energy levels and interactions in quantum precision measurements, but achieving precise measurements requires collaboration between the magnetic field system and the optical detection system. We propose a magnetic field system that incorporates a fast-switching magnetic field and an alternating magnetic field. Specifically, we enhance the switching speed by making structural improvements during the switching operation. An independent control approach is employed to reduce the switching time caused by electromagnetic induction across the coil using multilayer coils. The results demonstrate an inverse correlation between the rise and fall times of the magnetic field switch and the number of independently stacked coil layers, indicating the possibility of achieving further improvements in switching speed through structural enhancements. The system developed here has considerable potential for application to diverse quantum systems.

Impact of Rh, Ru, and Pd Leads and Contact Topologies on Performance of WSe2 FETs: A First Comparative Ab Initio Study.

2D field-effect transistors (FETs) fabricated with transition metal dichalcogenide (TMD) materials are a potential replacement for the silicon-based CMOS. However, the lack of advancement in p-type contact is also a key factor hindering TMD-based CMOS applications. The less investigated path towards improving electrical characteristics based on contact geometries with low contact resistance (RC) has also been established. Moreover, finding contact metals to reduce the RC is indeed one of the significant challenges in achieving the above goal. Our research provides the first comparative analysis of the three contact configurations for a WSe2 monolayer with different noble metals (Rh, Ru, and Pd) by employing ab initio density functional theory (DFT) and non-equilibrium Green's function (NEGF) methods. From the perspective of the contact topologies, the RC and minimum subthreshold slope (SSMIN) of all the conventional edge contacts are outperformed by the novel non-van der Waals (vdW) sandwich contacts. These non-vdW sandwich contacts reveal that their RC values are below 50 Ω∙μm, attributed to the narrow Schottky barrier widths (SBWs) and low Schottky barrier heights (SBHs). Not only are the RC values dramatically reduced by such novel contacts, but the SSMIN values are lower than 68 mV/dec. The new proposal offers the lowest RC and SSMIN, irrespective of the contact metals. Further considering the metal leads, the WSe2/Rh FETs based on the non-vdW sandwich contacts show a meager RC value of 33 Ω∙μm and an exceptional SSMIN of 63 mV/dec. The two calculated results present the smallest-ever values reported in our study, indicating that the non-vdW sandwich contacts with Rh leads can attain the best-case scenario. In contrast, the symmetric convex edge contacts with Pd leads cause the worst-case degradation, yielding an RC value of 213 Ω∙μm and an SSMIN value of 95 mV/dec. While all the WSe2/Ru FETs exhibit medium performances, the minimal shift in the transfer curves is interestingly advantageous to the circuit operation. Conclusively, the low-RC performances and the desirable SSMIN values are a combination of the contact geometries and metal leads. This innovation, achieved through noble metal leads in conjunction with the novel contact configurations, paves the way for a TMD-based CMOS with ultra-low RC and rapid switching speeds.

7‐1: Developing new Ferroelectric Liquid Crystal for LCOS

Ferroelectric liquid crystals (FLCs) have two attractive characteristics: very fast switching speeds and stable alignment against electrical fringe fields from neighboring pixels. However, care needs to be taken because FLC panels can be prone to alignment defects caused by Chevron structures. At this time, we have succeeded in developing a new FLC which has an improved temperature range, with a wider SmC phase, and which is more stable, thus making it less likely to have alignment defects. We look forward to demonstrating this to you with LCOS panels containing this new FLC.

Experimental demonstration of plasmon–plasmon scattering paves the way for electromagnetic wave-based digital logic concept

We report the experimental demonstration of plasmon–plasmon scattering at room temperature in the inversion layer of a patterned metal–oxide–semiconductor structure. This fundamental result paves the way for the development of plasmon–plasmon scattering logic, a revolutionary digital logic concept based on the generation, propagation, and manipulation of plasmons in an electron fluid, which was previously theoretically projected to exhibit femtojoule power dissipations and femtosecond switching speeds, while not demanding expensive nanometer-scale silicon (Si) technology fabrication processes for its implementation.

25‐1: Invited Paper: Technical Roadmap to Realize Reflective Full‐Color Video Displays for Street Furniture

Outdoor displays become rapidly digital in our digital world. These digital displays are typically emissive, implying a very high‐power consumption to be seen in the daylight, and light pollution in nighttime. Last year Etulipa announced and demonstrated a full colour reflective display based on Electro Wetting Display technology with 10mm pixel pitch. The vertically stacked Cyan Magenta Yellow architecture yields very bright colours. The high switching speed of electrowetting cells enable displaying of video content. The power consumption is 7 W/m 2 implying that the displays can run on solar systems without any need for charging from the grid. The market feedback consists of several exciting applications which are reviewed. Street furniture is expected to be a very early application. Because the typical viewing distance for street furniture applications will be in the order of meters, the pixel pitch should be in the order of millimeters. This requirement defines a technical roadmap for development of the existing electrowetting architecture.

Voltage Control of Multiple Electrochemical Processes during Lithium Ion Migration in NiFe2O4 Ferrite.

Li-ion-based electric field control has been attracting significant attention, since it is able to penetrate deep into materials to exhibit diverse and controllable electrochemical processes, which offer more degrees of freedom to design multifunctional devices with low power consumption. As opposed to previous studies that mainly focused on single lithiation/delithiation mechanisms, we reveal three Li-ion modulation mechanisms in the same NiFe2O4 spinel ferrite by in situ magnetometry, i.e., intercalation, conversion, and space charge, which are respectively demonstrated in high, medium, and low voltage range. During the intercalation stage, the spinel structure is preserved, and a reversible modulation of magnetization arises from the charge transfer-induced variation of Fe valence states (Fe2+/Fe3+). Conversion-driven change in magnetization is the largest up to 89 emu g-1, due to the structural and magnetic phase transitions. Although both intercalation and conversion exhibit sluggish kinetics and long response times, the space charge manifests a faster switching speed and superior durability due to its interface electrostatic effect. These results not only provide a clear and comprehensive understanding on Li-based modulation mechanisms but also facilitate multifunctional and multiscenario applications, such as multistate memory, micromagnetic actuation, artificial synapse, and energy storage.

Nanoscale Investigation of the Effect of Annealing Temperature on the Polarization Switching Dynamics of Hf0.5Zr0.5O2 Thin Films

AbstractRecently, HfO2‐based ferroelectric thin films have attracted widespread interest in developing next‐generation nonvolatile memories. To form a metastable ferroelectric orthorhombic phase in HfO2, a post‐annealing process is typically necessary. However, the microscopic mechanism underlying the effect of annealing temperature on ferroelectric domain nucleation and growth is still obscure, despite its importance in optimizing the operation speed of HfO2‐based devices. In this study, the ferroelectric properties and polarization switching of Hf0.5Zr0.5O2 thin films annealed at different temperatures (550–700 °C) are systematically investigated. Evidently, the crystal structure, remnant polarization, and dielectric constant monotonically change with annealing temperature. However, microscopic piezoresponse force microscopy images as well as macroscopic switching current measurements reveal non‐monotonic changes in the polarization switching speed with annealing temperature. This intriguing behavior is ascribed to the difference in the ferroelectric‐domain nucleation process induced by the amount of oxygen vacancies in the Hf0.5Zr0.5O2 thin films annealed at different temperatures. This work demonstrates that controlling the defect concentration of ferroelectric HfO2 by tuning the post‐annealing process is critical for optimizing device performance, particularly polarization switching speed.

Micromagnetic modeling of double spin-torque magnetic tunnel junction devices

Emerging nonvolatile magnetoresistive random access memory exhibits high endurance and long data retention compared to flash memory. Additionally, devices with double spin torque magnetic tunnel junctions (dsMTJ) featuring two magnetic reference layers demonstrate enhanced torques, fast switching, and reduced switching currents. To accurately model these devices, we adopt a coupled spin and charge transport approach allowing to describe spin-transfer torques in metallic spin valves and magnetic tunnel junctions on equal footing. Our findings indicate the critical influence of metallic non-magnetic spacers (NMS) properties separating the free layer from the second reference layer on the switching speed improvement in dsMTJ devices.

Nonvolatile bipolar resistive switching characteristics of aluminum oxide grown by thermal oxidation processes

This study proposes a bipolar resistive random-access memory (RRAM), which is fabricated using an aluminum oxide (AlO x ) resistive switching (RS) layer. The RRAM shows a large memory window of 106 at a low read voltage of 0.5 V. In addition, high switching speed, long retention time, and superior read-disturb immunity are observed. AlO x layers are prepared by a thermal oxidation growth process. Aluminum metal films deposited on n+-Si wafers are oxidized at O2/(O2 + N2) flow rate ratios of 50%–100%. Al/AlO x /n+-Si device shows no RS behavior when the AlO x is grown in a pure O2 environment. As the O2/(O2 + N2) flow rate ratio decreases to 50%, Al/AlO x :N/n+-Si device reveals stable bipolar RS characteristics. A filamentary mode based on oxygen interstitial and Al vacancy is proposed to explain the difference in electrical characteristics of AlO x devices prepared at different O2 flow rates.

A High-Voltage Pulse Modulator Composed of SiC MOSFETs/IGBTs in a Hybrid Connecting State

In order to solve problems such as a slow switching speed, a high switching power, a loss of pure IGBT modulators, and the weak withstanding load short-circuit ability of pure SiC MOSFET modulators used for vacuum loads, this paper proposes a new scheme for high-voltage pulse modulators based on SiC MOSFET/IGBT hybrid connecting circuits. It has a low power loss like the pure SiC MOSFET modulator and a strong withstanding load short-circuit ability like the pure IGBT modulator. Firstly, the principle circuit of the hybrid connecting modulator are discussed and chosen. And the basic working processes of the hybrid parallel-series modulator is described in detail. Secondly, three key points in this new scheme are analyzed and designed as follows: the static and dynamic voltage sharing; the actualizing of the ZVS process for IGBTs; the improvement of short-circuit protection for SiC MOSFETs. A modulator consisting of 16-stage 1200 V-SiC MOSFETs and 1200 V-IGBTs in hybrid parallel-series states is tested. Based on the sample circuit, the working data, such as high-voltage pulse waveforms of 10 kV/2 KHz/10 μs, static and dynamic voltage sharing, the driving control sequence, the U/I sequence of the IGBT, the short-circuit protection waveform, and the calculation, are obtained and discussed.

On-chip guided wave THz photonic switching with a phase change material on a dielectric waveguide encompassed with a novel micro-fins heater

On-chip photonic components, particularly for switching applications, are becoming more and more in demand to create high-density photonic integrated circuits in the THz regime. The nonvolatile switching can meet the requirement of power saving when the complexity of integrated circuits grows in the near future. Here, we propose and analyse the THz wave switching using a nonvolatile phase change material (PCM) Ge2Sb2Te5 (GST) integrated on a broadband THz dielectric waveguide that is encompassed by a novel micro-fins heater. In the proposed device, a small patch of GST of length 1500μm integrated on top of the HRFZ-Si waveguide provides an acceptable insertion loss and high extinction ratio for its broadband operation in the frequency span of 0.5–1.0 THz. Using a novel micro-fins heater, the phase transformation of the GST is carried out through Joule heating. Short electrical pulses of 11 ms and 4μs are found to be capable of raising the temperature of the GST region above its crystallization and re-amorphization temperature, respectively. The corresponding energy consumption for crystallization and re-amorphization is found to be 61.73 mJ and 19.84 mJ, respectively. The switching speed of our reported device is 100 times better than the previously reported metamaterial-based THz photonic switches using PCMs. Since GST is nonvolatile in nature, no continuous pump power is needed to maintain the particular switching state of the proposed device. The work reported here is a step forward for enabling THz photonic switching, and further THz circuits, in guided wave photonic platform using CMOS-compatible materials.

Si-CMOS compatible epsilon-near-zero metamaterial for two-color ultrafast all-optical switching

Driven by the escalating demands of advanced technologies, developing integration strategies has kept pace with the realization of ultrafast components during the past two decades. Ultrafast all-optical switches enabled by artificial materials are considered at the forefront of the next generation of photonic integration for communications and high-volume data processing. Encouraged by these advancements, applications, and interest have increased toward all-optical switches based on epsilon-near-zero (ENZ) materials. However, some all-optical switches lack CMOS compatibility, require high energy activation, and are limited in switching speed and working wavelength. Here, we propose and demonstrate a multilayered ENZ metamaterial utilizing Si-compatible titanium nitride and indium-tin-oxide materials with two effective working wavelengths in the visible and near-infrared spectrum. This device enables switching time down to a few hundred femtoseconds utilizing minimal energy at the corresponding ENZ regions induced by intraband pumping. Our approach can enhance the adaptability of designing ENZ metamaterials for new hybrid integrated photonic components for low-power ultrafast all-optical terahertz modulation.