Detection mechanism in highly sensitive ZnO nanowires network gas sensors

TL;DR

This paper investigates the non-linear response of ZnO nanowire network gas sensors, modeling the contributions of nanowire resistance and junction barriers to optimize sensor sensitivity and inform device design.

Contribution

It introduces a model that disentangles nanowire and junction effects in sensor response, guiding the design of more sensitive gas sensors based on ZnO nanowire networks.

Findings

Response to oxygen is dominated by barrier potential at low bias.

Nanowire resistance influences response at higher bias.

Optimal device geometry improves sensitivity.

Abstract

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.