High-response NO2 resistive gas sensor based on bilayer MoS2 grown by a new two-step chemical vapor deposition method

MoS2 atomic layers with a lateral grain size of 50-100 μm were synthesized by a new two-step chemical vapor deposition method. The product was confirmed to be bilayer MoS2 by the characterization of Raman spectroscopy, atomic force microscopy and high-resolution transmission electron microscopy. The growth mechanism and the influencing factors during the growth process of the bilayer MoS2 were proposed and the so-obtained large lateral grain sizes of MoS2 atomic layers were attributed to the high surface mobility and enhanced surface evaporation. The resistive gas sensors based on as-prepared bilayer MoS2 films showed a p-type character and achieved a superior sensitivity of 2.6% to 1 ppm NO2 gas at room temperature.