Graphene/LiNbO_3 surface acoustic wave device based relative humidity sensor

摘要

This study described relative humidity (RH) sensing using a graphene/128? YX LiNbO_3 surface acoustic wave (SAW) device. The resonant frequency of the device decreased in a two-stage manner as the RH increased. For a low RH range (RH< 50%), a frequency downshift of 1.38 kHz per 1% RH change was observed. This was attributed to mass loading of the SAW propagation surface due to the adsorption of water molecules by the graphene surface. For a high RH range (RH >50%), a frequency downshift of 2.6 kHz per 1% RH change was obtained, which was due to the change in elastic grapheme properties. The mass loading effect of the water layer was less effective at high temperature, resulting in a lower temperature coefficient of resonant frequency (TCF).