Selective Gas Sensing With $h$ -BN Capped MoS2 Heterostructure Thin-Film Transistors

Abstract

Owing to their ultimate surface-to-volume ratio two-dimensional (2D) van der Waals materials are candidates for flexible gas sensor applications. However, all demonstrated devices had relied on direct exposure of the active 2D channel to gases, which presents problems for their reliability and stability. We demonstrated, for the first time, selective gas sensing with molybdenum disulfide (MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) thin films transistors capped with a thin layer of hexagonal boron nitride (h-BN). The resistance change, AR/R, was used as a sensing parameter to detect chemical vapors. It was found that h-BN dielectric passivation layer does not prevent gas detection via changes in the current in the MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> channel. The detection without direct contacting the channel with analyte molecules was achieved with AR/R ratio as high as 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . In addition, we show that the use of h-BN cap layers (thickness H~10 nm) improves sensor stability and prevents degradation due to environmental and chemical exposure.