Effects of oxygen-functional groups on humidity sensor based graphene oxide thin films

In this work, we showed an effective method to control amount of oxygen-functional groups attached on graphene oxide (GO) by rapid thermal annealing (RTA) process. The GO thin films spraying on SiO₂/Si substrates from GO dispersion solution were annealed by RTA at various temperatures from 400 °C to 1200 °C. Resulting in significant reduced GO at 400 °C annealing temperature and removed most of the oxygen-containing functionalities from the annealing GO at 1200 °C. Along with a decrease resistance during increasing annealing temperature, the GO films loss its excellent absorption humidity vapor. The sensitivity (S) of humidity sensors fabricated on these GO films decreased from 35.3 % as-deposited GO to 0.075 % of 1200 °C annealing GO and the response time also increased in annealing samples. The highest sensitivity humidity can be obtained in as-deposited GO, but the humidity sensor-based graphene oxide have to trade-off between sensitivity and long-term stability, which is poor in as-deposited GO films.