Development of an Impedance-Based Electrical Humidity Sensor Using Sb-Doped Ge-Se-Te Chalcogenide Glasses

Abstract

The present paper demonstrates the effect of humidity on the (Ge11.5Te12.5Se67.5)80Sb20 and (Ge11.5 Te12.5Se67.5)70Sb30 thin film deposited on a glass substrate. The films prepared using a thermal evaporation technique reveal an amorphous nature as observed from the x-ray diffraction (XRD) graph. The light absorption taking place in the UV-visible region was confirmed using a UV–Vis spectrophotometer, and optical bandgap values of 1.46 eV and 1.42 eV were found for (Ge11.5Te12.5Se67.5)80Sb20 and (Ge11.5 Te12.5Se67.5)70Sb30 alloys using Tauc’s plot. The films were investigated for an impedance-based electrical humidity sensor. The maximum sensitivity of the chalcogenide sensing element was 13.86 MΩ/%RH and 15.31 MΩ/%RH for (Ge11.5Te12.5Se67.5)80Sb20 and (Ge11.5 Te12.5Se67.5)70Sb30, respectively, in the range 10–25%RH at room temperature, and the average sensitivity for the entire range of %RH was 7.33 MΩ/%RH and 9.42 MΩ/%RH, respectively, for the two glasses. The aging effect for samples was found to be negligible; hence they are stable against time, which makes them suitable for use as humidity sensors. The repeatability of the sensors was 89% and 94.45%, respectively.