Impact of Device Configurations on Sensing Performance of WS2-Based Gas Sensors: A Review

As 2D materials are aggressively penetrating the arena of conventional metal oxides-based gas sensors, tungsten disulfide (WS
₂
) as a ‘beyond graphene and beyond MoS
₂
layered material’ is appearing with shining visibility owing to its exquisite electronic, surface, optical, physicochemical and thermal properties. Micromechanically exfoliated or homogeneously/heterogeneously synthesized mono/few-layer(s) of this transition metal di-chalcogenide (TMDCs), with excellent tunability of almost all the properties, have intrigued worldwide gas sensor researchers to demonstrate various device configurations using WS
₂
leading to ultrahigh sensitivity with ppb level detection capacity even at room temperature. This review article presents a holistic overview of the WS
₂
based gas sensors encompassing the impact(s) of the different device architectures (viz. planar, Schottky, heterojunctions, field-effect, and heterojunction bipolar transistors) on the gas sensing performance indices (like sensitivity, selectivity, response/recovery time, humidity effect and baseline drift). Starting with the brief overview of the sensing mechanism of WS
₂
, followed by elaborate discussions on the unique features/advantages and bottlenecks of each of the innovative device architecture investigated, this review concludes by focusing the possible direction to circumvent the most common challenges (like slow and incomplete recovery, vulnerability to humidity and oxidation), that slacken the commercial viability of such devices.