On the performance of vertical MoS2 nanoflakes as a gas sensor

Abstract

Despite their potential applications, a limited number of studies for synthesizing vertical MoS2 nanoflakes especially via CVD have been reported so far, which generally involve tedious complex- and/or multi-step growth processes. In this study, direct synthesis of vertical MoS2 nanoflakes grown on the SiO2/Si substrate during a rapid sulfidation process by CVD method has been reported. Material characterization was performed using Raman spectroscopy, XRD and FE-SEM. The XRD results indicated the dominant phase of 2H–MoS2 within the synthesized layers. The characteristic distance between the two dominant peaks of E12g and A1g in the Raman spectra confirms the multi-layered structure for grown nanoflakes. Based on the experimental results, the growth mechanism has been explained considering nucleation and growth of two-dimensional islands, followed by coalescence of these islands. Subsequently, in the final stage, standing nanoflakes grow vertically. The vertical MoS2 nanoflakes film forms n-channel for back-gated FET gas sensor, of which gas sensing performance towards ethanol and methanol vapors have been studied. These structures with an increased number of edge sites presented high and fast responses to ethanol and methanol at 1 and 10 ppm concentrations and showed significant potential and promising application as a gas sensor transistor.