Nano-crystalline graphite for reliability improvement in MEM relay contacts

Abstract

Micro-and Nano-electromechanical (MEM/NEM) relays can operate with zero-leakage at far higher temperatures and levels of radiation than transistors, but have poor reliability. This work demonstrates improvement in reliability of MEM relays using nano-crystalline graphite (NCG)-coated contact surfaces. The high stability of NCG in ambient air, along with its low surface energy, appear to make it an ideal contact material. NCG-coated relays achieved over 2.8 million fast, hot-switching cycles with a drain current of at least 5 µA and on-resistance under 17 kΩ, in ambient air. The relays also were tested in slow, hot-switching cycles designed to increase the electrical stress on the contact, and consistently achieved on-currents up to 50 µA or the imposed current limit without failure. The eventual cause of failure appeared to be mechanical stress on the NCG layer over repeated cycling causing degradation. Increasing the layer thickness is expected to further improve the contact reliability. The relays are scalable and can be used as micro-or nano-scale switches in electronic components designed for very high temperatures and levels of radiation.

Nanocrystalline graphite thin layers for low-strain, high-sensitivity piezoresistive sensing

“…A proposed nomenclature for the diversified carbonic structures can be consulted in [23]. While respecting the aforementioned nomenclature as much as possible and considering its various characterizations [24][25][26], we define the material used in this work as bulk-NCG: a thick and hard carbonic film consisting of 3D randomly orientated, graphite nanocrystals with a dominant turbostratic packing [27] Thin films belonging to the broad class of NCG [27] have shown promise in applications such as: field emis-sion [28], electrochemical sensing [25,29,30], photodetection [31,32], nanoelectromechanical (NEM) switching [19], fabrication of microelectromechanical (MEM) resonators [20], protective coating [33] or gas separation [34]. The inhomogeneous conductive pathways formed by the sp 2 domains provide the material with a special functionality and a high conductivity response to small strains [10,18,35].…”

Sensing Performance of Nanocrystalline Graphite-Based Humidity Sensors

“…We used catalyst-free plasma-enhanced CVD (PECVD) to deposit NCG directly onto silicon dioxide substrates, as resistive humidity sensors. The NCG used here is a thicker variant of the nanocrystalline graphene films reported in [47], and similar to the NCG films reported in [46], [48]. The films are mechanically stable, are suitable for use in harsh environments, and have great mechanical wear resistance [48].…”

“…The NCG used here is a thicker variant of the nanocrystalline graphene films reported in [47], and similar to the NCG films reported in [46], [48]. The films are mechanically stable, are suitable for use in harsh environments, and have great mechanical wear resistance [48]. Using this technology, nanocrystalline graphite films with different film morphologies can be deposited by tuning the deposition parameters [49], [50].…”

Nanoelectromechanical relay without pull-in instability for high-temperature non-volatile memory

“…In all cycling experiments the mode of failure was deterioration of the Ti contacts, and although the relays continued to cycle mechanically, switching events could not be detected electrically. By combining this relay with a contact material that withstands mechanical wear better (such as carbon-based contact materials that have yielded the highest cycling results to date [21][22][23] or RuO 2 24 ), NEM relay-based reprogrammable non-volatile memory capable of >10 4 reprogramming cycles (typical of harsh-environment capable non-volatile memories) with better data retention and zero current leakage should be achievable. Such a robust relay also has potential for realisation of FPGAs with zero standby power for low throughput applications that require high-temperature capability 8 .…”