NO2 sensors based on crystalline MoSe2 porous nanowall thin films with vertically aligned molecular layers prepared by sputtering

Abstract

This work reports room temperature operable ultrasensitive NO2 gas sensors fabricated from vertically aligned crystalline MoSe2 porous nanowall thin films prepared by a facile and scalable DC sputtering technique at room temperature without any post-annealing and selenization treatment. The microstructural and compositional studies were carried out using XRD, Raman, FESEM, HRTEM, EDS and XPS to identify the quality and properties of the deposited MoSe2 thin films and to realize the underlying gas sensing mechanism. The NO2 gas sensing performance of vertically aligned MoSe2 porous nanowall thin film sensors was recorded over a wide range of NO2 gas concentrations (0.1–50 ppm) at room temperature (30 °C). The fabricated sensing device based on grown MoSe2 thin film exhibits excellent sensing characteristics (relative sensor response = –78.3% and response/ recovery time ~ 20 s/ 174 s for 10 ppm NO2 gas) along with high selectivity, real-time response, rapid on-off switching and adequate stability at room temperature. The observed substantial enhancement in sensing performance is attributed to the superior charge transfer process as a consequence of augmented adsorption of gas molecules mediated by the higher surface-to-volume ratio of the unique nanostructure, i.e., edge-enriched crystalline MoSe2 nanowalls along with the 3D porous surface structure in addition to the significant catalytic activity of MoSe2. Thus, this uniquely developed highly nanocrystalline sputtered MoSe2 porous nanowall thin films with vertically aligned molecular layers deposited at room temperature is cost-effective and highly desirable for developing low-powered high-performance gas sensors.