Effects of rapid thermal annealing on humidity sensor based on graphene oxide thin films

In this work, we demonstrate how to effectively use rapid thermal annealing (RTA) to control the quantity of oxygen functional groups attached on graphene oxide (GO). The GO thin films were sprayed from a GO dispersion solution onto SiO2/Si substrates and were annealed via RTA at various temperatures from 400 degrees C to 1200 degrees C. The proposed method results in a significant reduction of GO at an annealing temperature of 400 degrees C, and most oxygen-containing functionalities were removed by annealing the GO at 1200 degrees C. As the annealing temperature increased, the resistance decreased, and the GO films lost their excellent ability to absorb water vapor. The response (S) of humidity sensors fabricated on these GO films decreased from 35.3% for the as-deposited GO to 0.075% for the GO annealed at 1200 degrees C, and the response time also increased in the annealed samples. The highest response to humidity can be obtained in the as-deposited GO, but a trade-off exists between the response and the long-term stability of a humidity sensor based on graphene oxide since these are quite poor in as-deposited GO films. (C) 2015 Elsevier B.V. All rights reserved.