Fabrication of ethanol sensors based on ZnO thin film field-effect transistor prepared by thermal evaporation deposition

Abstract

© 2017 Elsevier Ltd. All rights reserved. The field effect transistor ethanol sensor with ZnO nanostructure as sensing layer were fabricated and their ethanol sensing properties at room temperature were investigated. The ZnO thin films were deposited on p-type Si substrate by thermal evaporation deposition and configured as bottom gate transistors. The electrical characteristics revealed n-channel semiconducting behavior with high on/off drain current ratio of ∼ 104, field effect mobility of about 0.90 cm2/Vs and threshold voltage of 2.8 V. Under the ethanol vapor atmosphere, it was found that the drain current at room temperature increased indicating higher conductance. The sensitivity was found to be about 3.0 at ethanol concentration of 100 ppm. These results indicate that the capture electrons were released by the reaction between the ethanol gas and the negatively charged ions and donating a few electrons back to the surface of ZnO resulting in an increased conductivity. The sensitivity of alcohol FET sensor could be modulated by negative gate bias voltage suggest that our device could be used as ethanol sensor at room temperature.