Selective Passivation of 2D TMD Surface Defects by Atomic Layer Deposited Al2O3 to Enhance Recovery Properties of Gas Sensor

Abstract

The incomplete recovery of TMD gas sensors hinders their reliability and scalability. [ The leading cause of incomplete recovery is the strong chemisorpt ion of gas analytes, such as defects or grain boundaries on the active surface of 2D TMDs. [ Here in, we demonstrate an improvement in the recovery rate of TMD gas sensors by selectively passivating the TMD surface defects or vacancies with Al 2 O 3 via atom ic layer deposition. Scanning electron microscopy analysis confirms that the nucleation and growth of atomic layer deposited Al 2 O 3 occur along the grain boundaries and defects of the 2D MoS 2 and WS 2 , not covering the inert basal plane. In addition, the Ram an, photoluminescence , and X ray photoelectron spectroscopy data show lower surface defect densities and a slight n doping effect of Al 2 O 3 . This unique selectively defect passivated TMD gas sensor show s a 400 % response toward 10 ppm of NO 2 , along with an increase in the recovery rate from 74 to 96 %, even at room temperature, as the number of atomic layer deposition cycles increases. Also, the recovery rate of NH 3 , a reducing gas, shows an increase of more than 30 %. Thus, the method proposed here is a pro mising strategy for improving the recovery rate of 2D TMD gas sensors.