Nanoelectromechanical Switches Research Articles

Lorentz Force-Actuated Bidirectional Nanoelectromechanical Switch with an Ultralow Operation Voltage.

The high operating voltage of conventional nanoelectromechanical switches, typically tens of volts, is much higher than the driving voltage of the complementary metal oxide semiconductor integrated circuit (∼1 V). Though the operating voltage can be reduced by adopting a narrow air gap, down to several nanometers, this leads to formidable manufacturing challenges and occasionally irreversible switch failures due to the surface adhesive force. Here, we demonstrate a new nanowire-morphed nanoelectromechanical (NW-NEM) switch structure with ultralow operation voltages. In contrast to conventional nanoelectromechanical switches actuated by unidirectional electrostatic attraction, the NW-NEM switch is bidirectionally driven by Lorentz force to allow the use of a large air gap for excellent electrical isolation, while achieving a record-low driving voltage of <0.2 V. Furthermore, the introduction of the Lorentz force allows the NW-NEM switch to effectively overcome the adhesion force to recover to the turn-off state.

Analytical Release Voltage Model of Monolithic 3-D Integrated Nanoelectromechanical Memory Switches

Analytical Release Voltage Model of Monolithic 3-D Integrated Nanoelectromechanical Memory Switches

Sub-0.3 volt amorphous metal WNx based NEMS switch with 8 trillion cycles

Introduction: The mechanical nature of nanoelectromechanical (NEM) switches makes them sluggish yet desirable for ultra-low-power, harsh environment applications. Two- and three-terminal NEM switches have been demonstrated using onedimensional, two-dimensional, and thin films, but sub-0.3 V operation with improved mechanical and electrical reliability is still elusive.Method: This study presents WNxnano-ribbon-based NEM sensor switches that operate at 0.6 V, 30 nanosecond switching time, 8 trillion cycles, and 0.5 mA ON current with less than 5 kΩ ON resistance, without stiction, mechanical welding, or short circuits. WNx’s high Young’s modulus gives it great elasticity and mechanical restoring force, which may overcome van der Waal and capillary forces.Results and Discussion: With its high Young’s modulus, the device’s nanoscale size facilitated low operating voltage. WNxnano-ribbon without grain boundaries is amorphous and more mechanically strong. Hammering and high current flow may destroy the nano-ribbon contact surface and interface, which is practically immaculate. Pull-out time (dominant delay factor) is 0 owing to high Young’s modulus, hence hysteresis loss and delay are absent. Elasticity and Young’s modulus increase speed.

Sub 0.5 Volt Graphene‐hBN van der Waals Nanoelectromechanical (NEM) Switches

AbstractThe Nanoelectromechanical (NEM) switches are a promising candidate to overcome the physical limitations of the complementary metal‐oxide‐semiconductor (CMOS) switches due to their quasi‐zero leakage behavior, sub‐thermal switching, and suitability to operate in harsh environments. The main obstacles affecting NEM switches are their irreversible switch‐contact stiction, the large switching voltage, and its hysteretic loop. In this study, the irreversible static friction is overcome by employing the weak van der Waals (vdW) bonding of graphene‐hexagonal boron nitride (hBN) contact in the Graphene NEM (GNEM) switches. These vdW switches show sub‐0.5 V switching voltage with an ON/OFF ratio higher than 105 and nearly zero hysteretic window characteristics with a high endurance of over 50 000 switching cycles. These remarkable performances are achieved by exploiting graphene's monolayer thickness, high Young's modulus, cubic mechanical restoring force, and low vdW binding energy characteristics. As chemical vapor deposition graphene and hBN are used in these GNEM switches, it exhibits the prospect for large‐scale graphene NEM system applications. These GNEM switches can be potentially used in ultralow‐power CMOS integrated circuits, hybrid NEM‐CMOS systems, logic devices, NEM resonator mass sensing, and single‐molecule sensors.

Application of Nondestructive Techniques to Investigate Dissolvable Amorphous Metal Tungsten Nitride for Transient Electronics and Devices

Transient electronics can be gradually dissolved in a variety of liquids over time. The short-lived nature of such electronics has promoted their implementation in prospective applications, such as implantable electronics, dissolvable devices for secure systems, and environmentally biodegradable electronics. The amorphous metal tungsten nitride (WNx) has the remarkable ability to scale down to the nano-scale, allowing the fabrication of sub-1 volt nano-electromechanical (NEM) switches. When compared to silicon, amorphous WNx has a greater density and electrical conductivity, making it an even more appealing material for the design of accelerometers and resistive temperature detectors. Kinetic hydrolysis is observed by the dissolution of amorphous WNx in ground water. To better understand the kinetics of hydrolysis, in this paper, samples are dissolved in different solutions under different conditions over time. NEM switches immersed in ground water, de-ionized (DI) water, and salty water are subjected to temperatures of 0 °C (degrees Celsius), 25 °C (room temperature, RT), and 60 °C. Sonicated samples are tested at both room temperature (RT) and at 60 °C. During the course of dissolving, the resistivity of amorphous WNx is measured, and an increase in resistance is noted when the thickness of the amorphous WNx is reduced. The wettability of a solid can be easily determined by measuring its contact angle, which indicates either the hydrophobic or hydrophilic nature of the surface. The contact angle of the amorphous WNx is measured to be about 30.8°, indicating hydrophilicity. For the temperature sensor characterization, a probe station with a thermal chuck is used to apply heat from the bottom of the sensor. The actual real-time temperature of the amorphous WNx sensor is measured using a thermocouple tip on the surface of the sensor.

Nonlocal Timoshenko shear beam model for multilayer curved graphene nano-switches

Graphene sheets are the basis of nano-electromechanical switches, which offer a unique insight into the world of quantum mechanics. In this paper, we proposed a new size-dependent multi-beam shear model for investigating the pull-in instability of multilayer graphene/substrate nano-switches within the context of the Timoshenko beam theory. As the graphene/substrate bemas bent toward the graphene layer due to the thermomechanical mismatch, the impact of curvature is considered in the proposed model. Also, the impact of the Casimir attraction is incorporated in the developed model by taking into account the limited conductivity of interacting surfaces. The scale dependency of the materials is considered in the framework of the nonlocal elasticity. To simulate the nano-switch and explore the pull-in instability, a finite element procedure is developed. The proposed approach is verified by comparing the pull-in voltage to published data. Finally, the role of influential parameters, including size dependency, length, initial gap, curvature, and the number of graphene layers on instability voltage of nano-switch, are investigated.

Bouncing dynamics of electrostatically actuated NEM switches

The aim of the present research is to understand the bouncing dynamic behavior of nanoelectromechanical (NEM) switches in order to improve switch performance and reliability. It is well known that bouncing can dramatically degrade the switch performance and life; hence, in the present study, the bouncing dynamics of a cantilever-based NEM switch has been studied in detail. To this end, the repulsive van der Waals force is incorporated into a nano-switch model to capture the contact dynamics. Intermolecular forces, surface effects, and gas rarefication effects were also included in the proposed model. The Euler–Bernoulli beam theory and an approximate approach based on Galerkin’s method have been employed to predict transient dynamic responses. In the present study, performance parameters such as initial contact time, permanent contact time, major bounce height, and the number of bounces, were quantified in the presence of interactive system nonlinearities. The performance parameters were used to investigate the influence of surface effects and rarefication effects on the performance of an electrostatically actuated switch. Recommended operating conditions are suggested to avoid excessive bouncing for these types of NEM switches.

Electrostatic pull-in application in flexible devices: A review

The electrostatic pull-in effect is a common phenomenon and a key parameter in the design of microscale and nanoscale devices. Flexible electronic devices based on the pull-in effect have attracted increasing attention due to their unique ductility. This review summarizes nanoelectromechanical switches made by flexible materials and classifies and discusses their applications in, among others, radio frequency systems, microfluidic systems, and electrostatic discharge protection. It is supposed to give researchers a more comprehensive understanding of the pull-in phenomenon and the development of its applications. Also, the review is meant to provide a reference for engineers to design and optimize devices.

Content-Addressable Memory System Using a Nanoelectromechanical Memory Switch

Content-addressable memory (CAM) performs a parallel search operation by comparing the search data with all content stored in memory during a single cycle, instead of finding the data using an address. Conventional CAM designs use a dynamic CMOS architecture for high matching speed and high density; however, such implementations require the use of system clocks, and thus, suffer from timing violations and design limitations, such as charge sharing. In this paper, we propose a static-based architecture for a low-power, high-speed binary CAM (BCAM) and ternary CAM (TCAM), using a nanoelectromechanical (NEM) memory switch for nonvolatile data storage. We designed the proposed CAM architectures on a 65 nm process node with a 1.2 V operating voltage. The results of the layout simulation show that the proposed design has up to 23% less propagation delay, three times less matching power, and 9.4 times less area than a conventional design.

Molecular Platform for Fast Low-Voltage Nanoelectromechanical Switching.

The use of molecules as active components to build nanometer-scale devices inspires emerging device concepts that employ the intrinsic functionality of molecules to address longstanding challenges facing nanoelectronics. Using molecules as controllable-length nanosprings, here we report the design and operation of a nanoelectromechanical (NEM) switch which overcomes the typical challenges of high actuation voltages and slow switching speeds for previous NEM technologies. Our NEM switches are hierarchically assembled using a molecular spacer layer sandwiched between atomically smooth electrodes, which defines a nanometer-scale electrode gap and can be electrostatically compressed to repeatedly modulate the tunneling current. The molecular layer and the top electrode structure serve as two degrees of design freedom with which to independently tailor static and dynamic device characteristics, enabling simultaneous low turn-on voltages (sub-3 V) and short switching delays (2 ns). This molecular platform with inherent nanoscale modularity provides a versatile strategy for engineering diverse high-performance and energy-efficient electromechanical devices.

Toward Monolithically Integrated Hybrid CMOS-NEM Circuits

Nanoelectromechanical (NEM) switches offer the advantages of zero OFF-state leakage current, abrupt switching characteristics, nonvolatile (NV) operation, and relatively low ON-state resistance as compared with CMOS transistors predominantly used for digital computing today. NEM switches can be implemented using metallic interconnect layers formed in the back-end-of-line (BEOL) steps of a standard CMOS IC manufacturing process, in order to enable compact implementation of hybrid CMOS-NEM circuits. In this article, a release-etch method is developed for realizing BEOL NV-NEM switches with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\leq 100$ </tex-math></inline-formula> -nm contact gaps. A functional array of BEOL NV-NEM switches is used to implement a hybrid CMOS-NEM IC for data search applications. NV-NEM switch design optimization to minimize the programming voltage and accelerate switching speed is discussed. A scaled NV-NEM technology is projected to be advantageous for high-speed, low-power reconfigurable computing applications. This projection is validated with experimental data for a BEOL NV-NEM switch implemented with a conventional 16-nm CMOS IC manufacturing process.

Cryogenic nanoelectromechanical switch enabled by Bi2Se3 nanoribbons

Nanoelectromechanical (NEM) switches are potential candidates for memory and logic devices for low standby-current and harsh environment applications. Cryogenic operation of these devices would allow to use them, e.g., in space probes and in conjunction with quantum computers. Herein, it is demonstrated that cryogenic application requirements such as good flexibility and conductivity are satisfied by using Bi2Se3 nanoribbons as active elements in NEM switches. Experimental proof of principle NEM switching at temperatures as low as 5 K is achieved in volatile and non-volatile reversible regimes, exhibiting distinct ON and OFF states, backed by theoretical modelling. The results open new avenues for research and development of NEM systems at cryogenic temperatures.

Nanoelectromechanical-Switch-Based Ternary Content-Addressable Memory (NEMTCAM)

A tristate-nanoelectromechanical-switch-based ternary content-addressable memory (NEMTCAM) is proposed for the first time. In the proposed unit NEMTCAM cell, a single nanoelectromechanical (NEM) memory switch replaces two static random access memory cells. Due to the monolithic 3-D (M3D) integration and nonvolatile property of NEM memory switches, the proposed NEMTCAM achieves an 86.3% smaller area, 75.0% lower dynamic power consumption, and a 76.6% higher search speed than conventional ternary content-addressable memory (TCAM) in addition to a negligible static leakage current.

Strain-induced switching in field effect transistor based on zigzag graphene nanoribbons

In this paper, we investigate the effects of uniaxial and oblique strain on Non-linear transport of zigzag graphene nanoribbons using non-equilibrium Green's function formalism. The current-voltage characteristics and especially negative differential resistance (NDR) are affected by the type, strength, and direction of the applied strain. For the tensile strain along the ribbon axis, the on-off current ratio increases, while for the compressive strain, NDR gradually disappears. In the oblique strain, the on-off current ratio drastically decreases compared to the un-strained case. In context, we demonstrate how strain can affect band structure and transition rules as well as transmission coefficients. Also in our calculations, we consider Coulomb interaction as long-range electrostatic potential at mean-field approximation. Coulomb interaction decreases off current and leads to the increased on-off current ratio in the oblique strain. Here, we observe under the influence of the oblique strain, the geometrical symmetry is broken, so the symmetry of charge profile and local currents are broken across ZGNR. We show an imbalanced accumulated charge located on the nanoribbon edges that as a consequence, appear some transverse local currents between the upper and lower edges. These transverse local currents are increased by the strain strength. The minimum (maximum) imbalanced charge accumulated on the ribbon edges occurs exactly at the on (off)-state of longitudinal bias where the transverse current is decreasing (increasing). Finally, we strongly suggest the strain can operate as a nanoelectromechanical switch.

Impact of Thermal Effects on the Performance of the Power Gating Circuits Using NEMS, FinFETs, and NWFETs

In this article, the power gating (PG) technique is analyzed using nano-electro-mechanical switches (NEMS), FinFETs, and nanowire field-effect transistors (NWFETs). We have used detailed circuit level simulations using well-calibrated models to obtain the conditions for net energy saving with thermal effects. We demonstrate that for a benchmark 17-stage buffer chain circuit, the NEMS PG will be superior to sub-10-nm FinFETs and NWFETs-based gating when the T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> on</sub> / T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> off</sub> ratio is less than 0.1 at room temperature. The ratio increases as temperature increases. Circuit simulations show that the energy gain ( T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> / T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> off</sub> = 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> ) due to NEMS gating increases by 3.6 times with reference to NWFETs and 7.3 times as compared to FinFETs-based gating when the temperature increases from 30 °C to 80 °C. NWFETs require a longer breakeven cycle for PG to become more energy-efficient than FinFETs due to its better gate control over the channel.

Efficient 1-V Boost Converter Using Sub-50-mV NEMS Without Body Bias

In this article, for the first time, we present the improvement in efficiency in a low-voltage dc-dc boost converter for the energy-harvesting applications using the experimentally demonstrated sub-50-mV nano electro-mechanical switch (NEMS). As per the measurement results, the sub-50-mV NEMS having a small air gap of only 100 nm exhibits very low hysteresis (<; 20 mV), low turn-on delay (15 ns), and low sub-threshold swing of 2 mV/decade. In addition to this, the fabricated NEMS is a propitious candidate toward ideal power switch with almost zero leakage current and a maximum ON-state conductance value of 0.1 A/(V·μm). This study explores a discontinuous-conduction mode (DCM) boost converter with specifications suitable for energy-harvesting applications using the NEMS-based design. The results are compared with the corresponding design using the MOSFET switches in 0.18- μm CMOS technology. This work illustrates that the NEMS-based DCM boost converter design has an improvement in the efficiency of around 30% at a switching frequency of 10 kHz over CMOS for the same ON-state resistance. This is because the proposed fabricated NEMS has extreme low pull-in voltage (50 mV) and low parasitic capacitances (~3.3 fF/μm).

Design, simulation and testing of an array of nano electro mechanical switches (NEMS)

Electro mechanical switches used for multi-purposs applications with ultra small size in nano meter scale, operating in very small voltage in millivolts, approximately zero leakage current due to air gap separation between electrodes with three terminals that easy to control it. Nano electro mechanical switches are electronic switches similar to those used by conventional semiconductor switches in application as they can be used as relays, logic devices. The basic principle of nano electro mechanical switches is electronic switches operation is fundamentally different from semiconductor switches. They have many advantages over conventional semiconductor switches such as low-power digital logic applications, ability to work with very small voltage signals for low dynamic energy consumption, and durability against hostile environments such as high temperatures and radiation contaminated spaces. In this article, we will design, implement, and test a matrix of nano electro mechanical switches by on line test using the superposition theory. The simulations of these switches were implemented using the MATLAB-Simulink and ORCAD Pspice environments. Also, controlling the flow of current was achieved by means of a nanometer movement to make or break the physical contact between the electrodes.

Design Technology Co-Optimization for Back-End-of-Line Nonvolatile NEM Switch Arrays

Design tradeoffs for vertically oriented nonvolatile (NV) nano-electro-mechanical (NEM) switches implemented using multiple interconnect layers in a 5-nm-generation CMOS back-end-of-line (BEOL) process are investigated via 3-D device simulation. Programming pulse voltage and width operating windows are identified for avoiding catastrophic pull-in. The simulation results indicate that sub-20-ns programming delay is possible with programming voltages compatible with standard input-output (I/O) CMOS circuitry, and that the write energy of an NV-NEM bit-cell will be less than 5 aJ. A crossbar array architecture operated with a half-select row/column bit-cell programming scheme is found to be effective for avoiding the issue of write disturbance.

Fabrication and Characterization of Double- and Single-Clamped CuO Nanowire Based Nanoelectromechanical Switches.

Electrostatically actuated nanoelectromechanical (NEM) switches hold promise for operation with sharply defined ON/OFF states, high ON/OFF current ratio, low OFF state power consumption, and a compact design. The present challenge for the development of nanoelectromechanical system (NEMS) technology is fabrication of single nanowire based NEM switches. In this work, we demonstrate the first application of CuO nanowires as NEM switch active elements. We develop bottom-up and top-down approaches for NEM switch fabrication, such as CuO nanowire synthesis, lithography, etching, dielectrophoretic alignment of nanowires on electrodes, and nanomanipulations for building devices that are suitable for scalable production. Theoretical modelling finds the device geometry that is necessary for volatile switching. The modelling results are validated by constructing gateless double-clamped and single-clamped devices on-chip that show robust and repeatable switching. The proposed design and fabrication route enable the scalable integration of bottom-up synthesized nanowires in NEMS.

Nanoelectromechanical-Switch-Based Binary Content-Addressable Memory (NEMBCAM)

This paper proposes a novel nanoelectromechanical-switch-based binary content-addressable memory (NEMBCAM) for the first time. A nanoelectromechanical (NEM) memory switch serves as both a nonvolatile memory and a switchable current path in an NEMBCAM unit cell. Owing to monolithic three-dimensional integration, NEMBCAM achieves a smaller unit cell area in comparison with conventional complementary metal–oxide–semiconductor-only binary content-addressable memory. Small unit cell area results in reduced match line (ML) capacitance, which lowers search energy consumption. Furthermore, a shorter search delay is achieved owing to the near-perfect on/off characteristic of the NEM memory switch.