Monolayer MoS2 and WSe2 Double Gate Field Effect Transistor as Super Nernst pH sensor and Nanobiosensor

Abstract

Two-dimensional layered material is touted as a replacement of current Si technology because of its ultra-thin body and high mobility. Prominent transition metal dichalcogenides (TMD), Molybdenum disulphide (MoS2), as a channel material for Field Effect Transistor has been used for sensing nano-biomolecules. Tungsten diselenide (WSe2), widely used as channel for logic applications, has also shown better performance than other 2D materials in many cases. pH sensor is integrated with Nanobiosensor most often since charges (value and type) of many biomolecules depend on pH of the solution. Ion Sensitive Field Effect Transistor with Silicon and III–V materials has been traditionally used for pH sensing. Experimental result for MoS2 field effect transistor as pH sensor has been reported in recent literature. However, no simulation-based study has been done for single layer TMD FET as pH sensor or bio sensor. In this paper, novel MoS2 and WSe2 monolayer double gate FETs are proposed for pH sensor operation in Super Nernst regime and protein detection. In case of pH sensing bottom gate operation ensures these monolayer FETs operating beyond Nernst limit of 59 mV/pH. Besides pH sensing, the proposed monolayer FETs also show reasonably high sensitivity in sub threshold region as protein detector. Simulation results found in this work reveal that, scaling of bottom gate oxide results in better sensitivity for both pH and biosensor while top oxide scaling exhibits an opposite trend in pH sensing. Keywords: Double gate FET, 2D material, pH sensor, Nernst limit, Drift diffusion, Nanobiosensor