Selectively Decorated Pt Nanoparticle on WS2 by Atomic Layer Deposition for Enhancing Recovery and Responsivity of NO2 Gas Sensor

Abstract

Need for gas sensing of trace amounts of nitrogen dioxide (NO2) has attracted great interest for environmental monitoring and health protection. Especially, two-dimensional transition metal dichalcogenides (2D TMDCs) based gas sensors have shown outstanding gas sensing properties even at room temperature. Moreover, functionalization of 2D TMDCs with noble metal nanoparticles (NM NPs) such as platinum nanoparticles (Pt NPs) is known to be effective way to greatly enhance the NO2 sensing properties by surface sensitization [1], and defect passivation. Defects such as dangling bonds or grain boundaries act as chemical adsorption site of NO2 gas, which deteriorate the recovery property of sensor [2]. However, due to the insufficient controllability of conventional NM NPs synthesis methods such as PVD and wet method, the NM NPs are easily agglomerated and not sufficiently dispersed onto 2D TMDC surfaces [3]. It can lead to incomplete recovery and poor stability of sensor. In this paper, we use atomic layer deposition (ALD) technique for well-dispersed Pt NPs on tungsten disulfide (WS2) and demonstrate the improvement of sensing properties of TMDC gas sensor by selective growth of NPs at surface defect sites. The NO2 gas response of Pt functionalized WS2 was increased up to 6 times (~850%, 10 ppm) for ALD 150 cycle compared to pristine WS2, and high recovery rate (~93.2%) was achieved for the 200 cycle. This proposed method shows a promising strategy for enhancing the properties of TMDC gas sensors operating at room temperature and increasing the controllability of surface functionalization.