Highly selective and reversible NO gas sensor using vertically aligned MoS flake networks.

We demonstrate a highly selective and reversible NO resistive gas sensor using vertically aligned MoS (VA-MoS) flake networks. We synthesized horizontally and vertically aligned MoS flakes on SiO/Si substrate using a kinetically controlled rapid growth CVD process. Uniformly interconnected MoS flakes and their orientation were confirmed by scanning electron microscopy, x-ray diffraction, Raman spectroscopy and x-ray photoelectron spectroscopy. The VA-MoS gas sensor showed two times higher response to NO compared to horizontally aligned MoS at room temperature. Moreover, the sensors exhibited a dramatically improved complete recovery upon NO exposure at its low optimum operating temperatures (100 °C). In addition, the sensing performance of the sensors was investigated with exposure to various gases such as NH, CO, H, CH and HS. It was observed that high response to gas directly correlates with the strong interaction of gas molecules on edge sites of the VA-MoS. The VA-MoS gas sensor exhibited high response with good reversibility and selectivity towards NO as a result of the high aspect ratio as well as high adsorption energy on exposed edge sites.