  Metal-oxide nanowires are showing a great interest in the domain of gas
sensing due to their large response even at a low temperature, enabling
low-power gas sensors. However their response is still not fully understood,
and mainly restricted to the linear response regime, which limits the design of
appropriate sensors for specific applications. Here we analyse the non-linear
response of a sensor based on ZnO nanowires network, both as a function of the
device geometry and as a response to oxygen exposure. Using an appropriate
model, we disentangle the contribution of the nanowire resistance and of the
junctions between nanowires in the network. The applied model shows a very good
consistency with the experimental data, allowing us to demonstrate that the
response to oxygen at room temperature is dominated by the barrier potential at
low bias voltage, and that the nanowire resistance starts to play a role at
higher bias voltage. This analysis allows us to find the appropriate device
geometry and working point in order to optimize the sensitivity. Such analysis
is important for providing design rules, not only for sensing devices, but also
for applications in electronics and opto-electronics using nanostructures
networks with different materials and geometries.
