A Highly Reliable Two-Axis MEMS Relay Demonstrating a Novel Contact Refresh Method

Yoo

et al. 2020

Advanced Materials

Recently, geometrically structured nanomaterials have received great attention due to their unique physical and chemical properties, which originate from the geometric variation in such materials. Indeed, the use of various geometrically structured nanomaterials has been actively reported in enhanced‐performance devices in a wide range of applications. Recent significant progress in the development of geometrically structured nanomaterials and associated devices is summarized. First, a brief introduction of advanced nanofabrication methods that enable the fabrication of various geometrically structured nanomaterials is given, and then the performance enhancements achieved in devices utilizing these nanomaterials, namely, i) physical and gas nanosensors, ii) nanoelectromechanical devices, and iii) nanosieves are described. For the device applications, a systematic summary of their structures, working mechanisms, fabrication methods, and output performance is provided. Particular focus is given to how device performance can be enhanced through the geometric structures of the nanomaterials. Finally, perspectives on the development of novel nanomaterial structures and associated devices are presented.

Section: High‐performance Nems/mems Devicesmentioning

confidence: 99%

Section: High‐performance Nems/mems Devicesmentioning

confidence: 99%

Geometrically Structured Nanomaterials for Nanosensors, NEMS, and Nanosieves

Yoo

et al. 2020

Advanced Materials

“…However, the low elastic modulus, low melting point, and high ductility of Au lead to surface damages in the case of repeated contact loading, thus limiting the stable and repetitive operation of the switches . Recently, a broad range of materials and structural designs of the switches have been proposed to improve their lifetimes. − For example, the switches based on metal alloys, ruthenium, or silicon carbide have shown improved contact lifetimes. − Moreover, there have been studies about all metal-based NEM switches to improve the lifetime with a reduced contact resistance. , For example, Qian et al. reported studies about NEM switches fabricated by molybdenum (Mo) as contact material and structure by a single lithography step, and thus achieved a decreased contact resistance of several kiloohms even at the nanoscale contact area, which also showed repeatable operations at high temperature.…”

Section: Introductionmentioning

confidence: 99%

Integration of a Carbon Nanotube Network on a Microelectromechanical Switch for Ultralong Contact Lifetime

ACS Appl. Mater. Interfaces

Pyo

et al. 2019

Self Cite

Micro-/nanoelectromechanical (MEM/NEM) switches have been extensively studied to address the limitations of transistors, such as the increased standby power consumption and performance dependence on temperature and radiation. However, their lifetimes are limited owing to the degradation of the contact surfaces. Even though several materials and structural designs have been recently developed to improve the lifetime, the production of a microswitch that is compatible with a complementary metal-oxide semiconductor (CMOS) with a long lifetime remains a significant challenge. We demonstrate a vertically actuated MEM switch with extremely high reliability by integrating a carbon nanotube (CNT) network on a gold electrode as the contact material using a low-temperature, CMOS-compatible solution process. In addition to their outstanding mechanical and electrical properties of CNTs, their deformability dramatically increases the effective contact area of the switch, thus resulting in the extension of the lifetime. The CNT-coated MEM switch exhibits a lifetime that is more than 7 × 108 cycles when operated in hot-switching conditions, which is 1.9 × 104 times longer than that of a control device without CNTs. The switch also shows an excellent switching performance, including a low electrical resistance, high on/off ratio, and an extremely small off-state current.

“…In general, the actual operation of M/NEM switching devices consists of "contact−separation" of a large number of atomicand nano-asperities at the contacting interface. 25,35 These contacting spots are too tiny to perform a specific analysis of nanoscale contact phenomena such as wear. The difficulty in manufacturing is another reason.…”

Section: Introductionmentioning

confidence: 99%

>1000-Fold Lifetime Extension of a Nickel Electromechanical Contact Device via Graphene

ACS Appl. Mater. Interfaces

Lee

et al. 2018

Self Cite

Micro-/nano-electromechanical (M/NEM) switches have received significant attention as promising switching devices for a wide range of applications such as computing, radio frequency communication, and power gating devices. However, M/NEM switches still suffer from unacceptably low reliability because of irreversible degradation at the contacting interfaces, hindering adoption in practical applications and further development. Here, we evaluate and verify graphene as a contact material for reliability-enhanced M/NEM switching devices. Atomic force microscopy experiments and quantum mechanics calculations reveal that energy-efficient mechanical contact-separation characteristics are achieved when a few layers of graphene are used as a contact material on a nickel surface, reducing the energy dissipation by 96.6% relative to that of a bare nickel surface. Importantly, graphene displays almost elastic contact-separation, indicating that little atomic-scale wear, including plastic deformation, fracture, and atomic attrition, is generated. We also develop a feasible fabrication method to demonstrate a MEM switch, which has high-quality graphene as the contact material, and verify that the devices with graphene show mechanically stable and elastic-like contact properties, consistent with our nanoscale contact experiment. The graphene coating extends the switch lifetime >10 times under hot switching conditions.