Nanoelectromechanical Research Articles

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.

Ultrahigh-quality graphene resonators by liquid-based strain-engineering.

Two-dimensional (2D) material-based nanoelectromechanical (NEM) resonators are expected to be enabling components in hybrid qubits that couple mechanical and electromagnetic degrees of freedom. However, challenges in their sensitivity and coherence time have to be overcome to realize such mechanohybrid quantum systems. We here demonstrate the potential of strain engineering to realize 2D material-based resonators with unprecedented performance. A liquid-based tension process was shown to enhance the resonance frequency and quality factor of graphene resonators six-fold. Spectroscopic and microscopic characterization reveals a surface-energy enhanced wall interaction as the origin of this effect. The response of our tensioned resonators is not limited by external loss factors and exhibits near-ideal internal losses, yielding superior resonance frequencies and quality factors to all previously reported 2D material devices. Our approach represents a powerful method of enhancing 2D NEM resonators for future quantum systems.

Nanoprobe Based Information Processing: Nanoprobe‐Electronics

AbstractWith computational architectures becoming data‐centric and with the rise of in‐memory computing, the role of memory will be ever more crucial. In turn, storing massive amount of data demands for ultra‐low power and non‐volatile types necessitating new memory technologies. Here, a controllable nanoelectromechanical (NEM) spin memory is proposed for compact nonvolatile memory arrays. It combines the advantages of both nanomechanical and spin‐transfer torque (STT) magnetic memory devices to overcome fundamental scalability roadblocks of non‐hybrid alternatives. The hybrid system paves the way to a new memory technology in the regime of sub‐10‐nm lateral size with a sub‐1‐MA cm−2 switching energy.

Surface Effect in Nano-Scale Fretting Contact Problems

Abstract The fretting contact behavior of nanostructured materials is significantly influenced by the surface effect. A model of fretting contact between a nano-sized rigid cylindrical indenter and an elastic half-plane is established based on Gurtin–Murdoch (G–M) surface elasticity theory, with which the surface effects on the stress and displacement distributions and the size of stick region (no-slip region) in the contact zone are systematically studied. It is found that the surface effect induces an additional traction besides the external force applied by punch, which could help to smoothen the stress and displacement distributions. The normal surface-induced traction related to the residual surface stress is opposite to the externally applied compression, which results in a material stiffening in the contact zone so that the contact radius, normal displacement, and normal stress decrease compared with their classical counterparts. The tangential surface-induced traction is also opposite to the externally applied frictional stress, consequently leading to reductions of the shear stress and tangential displacement induced by friction in the contact zone. More interestingly, the surface effect leads to three possible states in the contact zone, including complete slip, partial slip, and complete stick, instead of the solely partial slip state in classical fretting contact models without surface effect. Among them, the complete stick due to the action of surface residual stress is more beneficial for inhibiting the wear of contact devices, which can be realized by reducing the indenter size. The present research does not only help one to better understand the physical mechanism in nano-scale fretting contact problems, but should also guide the anti-wear design in nano-electro-mechanical (NEMs) systems.

Large Scale Fabrication of Graphene Based Nano‐Electromechanical (NEM) Contact Switches with Sub‐0.5 Volt Actuation (Adv. Phys. Res. 4/2023)

Nano-Electromechanical Contact Switches Nano-electromechanical (NEM) contact switches based on graphene–graphene van der Waals contacts are demonstrated by Jothiramalingam Kulothungan and Karthi Kandhasamy in article number 2200050. Graphene–graphene NEM contact switches with ultra-low pull-in voltage and significant improvement in the contact lifetime are achieved using the graphene on gold electrode as a contact material. The graphene NEM contact switches with graphene as a contact material exhibits an ultra-low pull-in voltage of < 0.5 V and high contact lifetime, suitable for a new generation of energy efficient electronics.

Integrated 4-terminal single-contact nanoelectromechanical relays implemented in a silicon-on-insulator foundry process.

Integrated nanoelectromechanical (NEM) relays can be used instead of transistors to implement ultra-low power logic circuits, due to their abrupt turn off characteristics and zero off-state leakage. Further, realizing circuits with 4-terminal (4-T) NEM relays enables significant reduction in circuit device count compared to conventional transistor circuits. For practical 4-T NEM circuits, however, the relays need to be miniaturized and integrated with high-density back-end-of-line (BEOL) interconnects, which is challenging and has not been realized to date. Here, we present electrostatically actuated silicon 4-T NEM relays that are integrated with multi-layer BEOL metal interconnects, implemented using a commercial silicon-on-insulator (SOI) foundry process. We demonstrate 4-T switching and the use of body-biasing to reduce pull-in voltage of a relay with a 300 nm airgap, from 15.8 V to 7.8 V, consistent with predictions of the finite-element model. Our 4-T NEM relay technology enables new possibilities for realizing NEM-based circuits for applications demanding harsh environment computation and zero standby power, in industries such as automotive, Internet-of-Things, and aerospace.

Non-Volatile Nano-Electro-Mechanical Switches and Hybrid Circuits in a 16 nm CMOS Back-End-of-Line Process

Reprogrammable non-volatile (NV) vertically-oriented nano-electro-mechanical (NEM) switches with a compact footprint are successfully implemented using multiple back-end-of-line (BEOL) interconnect layers of a standard 16-nm CMOS process technology, with no additional lithography steps. A compact decoder circuit comprising an array of these reconfigurable interconnects is successfully demonstrated. As the minimum metal pitch decreases with each new manufacturing process generation, hybrid CMOS+NEM technology becomes increasingly attractive for ultra-low-power reconfigurable computing applications.

Large Scale Fabrication of Graphene Based Nano‐Electromechanical (NEM) Contact Switches with Sub‐0.5 Volt Actuation

AbstractNano‐electromechanical (NEM) contact switches are extensively studied to suppress the limitations of conventional complementary metal‐oxide‐semiconductor (CMOS) transistors. The attributes of NEM contact switches includes reduced power consumption, reduced off‐state leakage current, and increased on‐state current and sub‐thermal switching. However, unacceptably high pull‐in voltage and low contact lifetime posed a significant challenge for the use of NEM contact switches in energy efficient CMOS applications. Here, graphene‐based electro‐statically actuated NEM contact switches with ultra‐low pull‐in voltage and significant improvement in the contact lifetime are demonstrated. This is achieved by using the graphene on gold electrode as a contact material. The graphene NEM contact switches with graphene as a contact material exhibit an ultra‐low pull‐in voltage of &lt; 0.5 V and high contact lifetime of more than 1.5× 106 cycles. The switches also show an excellent switching performance with high on/off ratio of ≈108, an extremely low off‐state current of ≈100 fA, and small hysteresis window of &lt; 0.1 V.

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.

3-D coarse-grained reconfigurable array using multi-pole NEM relays for programmable routing

We propose the use of multi-pole nanoelectromechanical (NEM) relays for routing multi-bit signals within a coarse-grained reconfigurable array (CGRA). We describe a CMOS-compatible multi-pole relay design that can be integrated in 3-D and improves area utilization by 40% over a prior design. We then demonstrate a method for placing multiple contacts on a relay that can reduce contact resistance variation by 40× over a circular placement strategy. Additionally, we develop static and dynamic SPICE models (calibrated to accurate finite element models) for predicting circuit-level performance with these devices. Finally, we establish a methodology for integrating these relays into an industry-standard digital design flow. Using our multi-pole relay design, we perform post-layout simulation of a hybrid CMOS-NEMS CGRA processing element (PE) tile in 40 nm technology. We achieve up to 19% lower area and 10% lower power at iso-delay, compared to a CMOS-only CGRA PE tile. The results show a way to bridge the performance gap between programmable logic devices (such as CGRAs) and application-specific integrated circuits using NEMS technology.

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.

Nanoelectromechanical (NEM) Devices for Logic and Memory Applications

Recent research on NEM devices for logic and memory applications has been reviewed from the perspective of monolithic 3D (M3D) heterogeneous integration. In addition, the backgrounds of M3D CMOS-NEM reconfigurable logic (RL) circuits are described in detail. Moreover, 65-nm process based M3D CMOS-NEM RL circuits were proposed. It is predicted that proposed M3D CMOS-NEM RL circuits will exhibit 4.6x higher chip density, 2.3x higher operation frequency and 9.3x lower power consumption than CMOS-only ones (tri-state buffer case) for tile-to-tile operation.

MEMS and NEMS - micro (and nano) electromechanical systems

MEMS and NEMS use and application is growing and their market is expanding. With the development of 5G and IoT technologies the number of MEMS components is always increasing. In this paper an introduction to MEMS/NEMS definition, categories, and advantages. Fabrication techniques of MEMS/NEMS are discussed. Finally, an elaborative analysis of the different applications of MEMS/NEMS, followed by a discussion of the future of Micro / Nano electromechanical Systems.

MEMS and NEMS - micro (and nano) electromechanical systems

MEMS and NEMS use and application is growing and their market is expanding. With the development of 5G and IoT technologies the number of MEMS components is always increasing. In this paper an introduction to MEMS/NEMS definition, categories, and advantages. Fabrication techniques of MEMS/NEMS are discussed. Finally, an elaborative analysis of the different applications of MEMS/NEMS, followed by a discussion of the future of Micro / Nano electromechanical Systems.

Frictional Behavior of Alumina-Coated Vertically Aligned Carbon Nanotube Forests: Implications for Micro and Nano Electromechanical Devices

Frictional Behavior of Alumina-Coated Vertically Aligned Carbon Nanotube Forests: Implications for Micro and Nano Electromechanical Devices

Frequency shifts and thermoelastic damping in distinct Micro-/Nano-scale piezothermoelastic fiber-reinforced composite beams under three heat conduction models

The present work aims to fulfill two primary objectives. Firstly, to present the micro-mechanics model of piezothermoelastic fiber-reinforced composite (PTFRC) medium using analytical techniques, viz., Strength of Materials (SM) & Rule of Mixtures (RM) and graphically establish some of its electro-mechanical-thermal advantages over monolithic PT materials. Secondly, to analytically study the thermoelastic damping (TED) and frequency shift (FS) in micro-/nano-scale PTFRC beams. TED and FS are analyzed considering the linear Euler-Bernoulli theory when the beam is under four distinct boundary conditions, viz., clamped-clamped (CC), simply supported-simply supported (SS), clamped-free (CF), and clamped-simply supported (CS). The eigenvalues of each beam are calculated numerically with 20 iterations each using the Newton-Raphson technique, followed by the analysis of TED and FS considering the assumed boundaries. The Classical dynamical coupled (CL), Lord-Shulman (LS), and Green-Lindsay (GL) thermoelasticity theories are exclusively analyzed. The effects of thermal relaxation parameters, fiber volume fraction, micro and nano beam dimensions, and the first two modes (M1 & M2) on the TED and FS are graphically illustrated. The critical thickness (CrTh) and critical length (CrLt) of all four beams influenced by the existing parameters are scrupulously investigated. The robustness of the obtained results is validated by matching them with previous literature. For high Ωf, the PTFRC beam has superior electro-mechanical-thermal properties and greater Q-factors compared to monolithic beam. However, the Q-factor increases as Ωf decreases. This facilitates the choice of a suitable value of Ωf for designing and optimizing frequency-sensitive microelectromechanical (MEM) and nanoelectromechanical (NEM) PTFRC beams.

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.

Theory, Design, and Characterization of Nanoelectromechanical Relays for Stiction-Based Non-Volatile Memory

Diverse areas such as the Internet of Things (IoT), aerospace and industrial electronics increasingly require non-volatile memory to work under high-temperature, radiation-hard conditions, with zero standby power. Nanoelectromechanical (NEM) relays uniquely have the potential to work at 300 °C and absorb high levels of radiation, with zero leakage current across the entire operational range. While NEM relays that utilise stiction for non-volatile operation have been demonstrated, it is not clear how to design a relay to reliably achieve given programming and reprogramming voltages, an essential requirement in producing a memory. Here, we develop an analytical, first-principle physics-based model of rotational NEM relays to provide detailed understanding of how the programming and reprogramming voltages vary based on the device dimensions and surface adhesion force. We then carry out an experimental parametric study of relays with a critical dimension of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\approx ~\mathrm {80~~\, \text {n} \text {m} }$ </tex-math></inline-formula> to characterise the surface adhesion force, and derive guidelines for how a NEM relay should be dimensioned for a given contact surface force, feature size constraints and operating requirements. We carry out a scaling study to show that voltages of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\approx ~\mathrm {1~~\, \text {V}}$ </tex-math></inline-formula> and a footprint under <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\approx ~\mathrm {2~~\, \mu \text {m} ^{2}}$ </tex-math></inline-formula> can be achieved with a critical dimension of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\approx ~\mathrm {10~~\, \text {n} \text {m} }$ </tex-math></inline-formula> , with this device architecture. [2021-0138]

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.