The geometrical dependence
of humidity sensors on sensing performance
has not been quantitatively outlined. Furthermore, the etching effect
on humidity sensors is still elusive due to the difficulty in separating
the effects of the geometrical change and etching-induced porosity
on the overall performance. Here, we use COMSOL Multiphysics to perform
a numerical study of a capacitive graphene oxide (GO) humidity sensor,
with emphasis on the dimensions and etching effect on their sensing
performance. GO is a useful and promising material in detecting humidity
because of its selective superpermeability to water molecules. The
mechanism of improved sensing performance of the etched humidity sensors
is discussed in terms of the morphological profile and the effective
permittivity including the etching-induced porosity effect. Our study
shows that as compared to the unetched sensors, isotropic etching
achieves the lowest response time of 1.011 s at 15.75% porosity, while
vertical etching achieves the highest capacitance sensitivity of 0.106
fF/RH %.