Selectively Decorated Pt Nanoparticle on WS2 by Atomic Layer Deposition for High-Performance Gas Sensor

Abstract

Two-dimensional transition metal dichalcogenides (2D TMDCs) have attracted much attention in many research fields owing to their remarkable electrical, chemical, and optical properties. In addition, 2D TMDC-based gas sensor indicates significant gas detection characteristics at room temperature, opposed to the oxide-based sensor which requires external heating for gas detection.1 Therefore, various 2D TMDC gas sensor studies have been conducted, and as the use of gas sensor expands, performance improvement becomes the challenge of TMDC gas sensors. Sensing characteristics of 2D TMDC can be enhanced via functionalizing with a noble metal such as Pt, Au, Pd. Among them, Pt is known as a highly effective oxidation catalyst, and Pt nanoparticles (Pt NPs) can make sensing surface more sensitive to gas molecules owing to electronic sensitization and spillover effects.2 In contrast, as the Pt NPs are difficult to form, atomic layer deposition (ALD) is used to precisely control atomic-scale deposits. In this study, ALD Pt decorated tungsten disulfide (WS2) was used as a sensing channel to maximize the response of the gas sensor. Pt NPs preferentially grew at higher surface energy point such as dangling bonds and grain boundaries of WS2. Then, sensing characteristics of selectively decorated on WS2 gas sensor was evaluated by various gases. It showed that the NO2 response extremely increased with the number of ALD cycles. However, when the Pt film was formed at the increased number of cycles, the response decreased due to the loss of the semiconducting property of WS2. Thus, we could investigate the proper number of cycles for maximizing the sensing response. In addition, it showed that the selectivity of the gas sensor could also be improved by the ALD Pt process.