An Impedance Humidity Sensor Based on CVD Grown WSe2 2D Films

Abstract

2D materials-based planar devices have been sought after for gas and humidity sensor applications owing to their highsensitivity due to their ultrathin nature and increased surface area. Herein, 2D WSe2 films-based planner devices were fabricated toevaluate their performance for potential application in humidity sensors. The structure and morphology of the WSe2 sensing filmswere studied by Raman spectroscopy, photoluminescence, optical microscopy, and scanning electron microscopy (SEM) techniques.The relative humidity-dependent sensing performances of the 2D WSe2 films were evaluated using current−voltage (I−V), relativeimpedance, and complex total impedance (electrochemical impedance spectroscopy, EIS) techniques. This sensor showed a verystable and repeatable performance investigated over the period of 18 months. The response and recovery times of the WSe2-basedimpedance sensors were found to be 40 and 30 s, respectively. The WSe2 sensor exhibits a 2 ± 1% minimum hysteresis at a lowerhumidity level (50% RH) and around 8 ± 2% maximum hysteresis at relative humidity level (70% RH). This value of hysteresis is inthe acceptable range during the initial investigation of any material to explore its potential for application in humidity sensors. Thedensity functional theory (DFT) analysis was performed with the interaction from water molecules of the WSe2 sample for a betterunderstanding of the sensing mechanism of devices