(Invited) Graphene Nano-Electro-Mechanical (NEM) Devices and Extension to Sensor Applications

Abstract

Graphene, as a monolayer of graphite, has an ultra-high Young’s modulus of ~1 TPa, which makes it a promising candidate for Nano-Electromechanical (NEM) devices. Thanks to highly-stable SP2 bonds in a 2D honeycomb lattice, graphene also features an extremely suppressed electrical noise, making it possible to realize extremly-sensitive sensor. This paper presents an overview on our recent study of novel graphene NEM devices for abrupt switching and ultra-sensitive chemical gas sensing applications. The graphene NEM switches are expected to show minimized electrical leakage, sharp switching response, low actuation voltage, and a high on/off ratio. Three-terminal graphene NEM switches with heterogeneously stacked graphene / h-BN layers are developed, which achieve low-voltage and sub-thermal switching (S ～ 10 mV/dec) at room temperature [1]. We then present nanoscale graphene gas sensors, which detect either resistance or mass changes due to a small number of gas molecules physisorbed onto suspended graphene at room temperature. With the resistance detection method, we show quantized increments in the temporal resistance of approximately 60 Ohm, signifying single CO2 molecule adsorption onto a suspended graphene channel [2][3]. As for the mass detection method, we demonstrate the resonance frequency shift of a doubly-clamped graphene resonator with the mass resolution of hundreds zeotpgram (10-21 g) order [4][5]. We also introduce recent experimental work of applying these graphene nanosensors to detect gas emanated from human skin such as NH3 and acetone of very low concentration of down to ppb level. This research was supported through the Grant-in-Aid for Scientific Research KAKENHI (18H03861, 18K04260, 25220904) from JSPS, COI program of the Japan Science Technology Agency and collaboration grant by TAIYO YUDEN Co. Ltd. [1] N. H. Van, M. Muruganathan, J. Kulothungan and H. Mizuta, Nanoscale 10, 12349-12355 (2018) [2] J. Sun, M. Muruganathan, and H. Mizuta, Sci. Adv., 2, e1501518–e1501518 (2016) [3] M. Muruganathan, J. Sun, T. Imamura, and H. Mizuta. Nano letters 15, 8176 (2015) [4] M. Muruganathan, F. Seto, and H. Mizuta, IJAT 12(1) 24-28 (2018) [5] M. Muruganathan, H. Miyashita, J. Kulothungan, M. Schmidt, H. Mizuta, IEEE Sensors 2018, New Delhi, India, October (2018)