Surface Potential-Based Approach to Estimate Bias Dependent Sensitivity of 1-D Metal Oxide Resistive Gas Sensors

The current work concern a surface potential based approach to study the bias voltage dependent sensitivity of 1-D metal oxide gas sensors. Bias dependent sensitivity for granular metal oxide gas sensors has already been reported. Considering the wide applicability of 1-D nanomaterials in gas sensing application, the bias dependent sensitivity has been studied in present work by theoretical route which was supported by experimental findings. The concept was established based on the surface potential ( $\Psi _{{\mathbf {S}}}$ ) effect due to the carrier concentration gradient by surface adsorption of gases on the metal oxide. Considering the effect of both the potentials i.e. $\Psi _{{\mathbf {S}}}$ and bias voltage, the exact bias point was found to get the peak response of 1-D metal oxide gas sensor. TiO2 nanotubes array was considered as the test sensing material. In the first phase of the article, the theoretical approach has been reported to estimate the sensor response of 1-D nanotubes and in the second phase of the study, the theoretical concept has been justified with experimental results. Highly oriented TiO2 nanotube array was synthesized, characterized and used to fabricate Au/TiO2 nanotubes/Ti type vertical structured sensor device. Simulation results exhibited the highest response of the TiO2 nanotube sensor in-between 0.1-0.4 V of bias voltage which was then authenticated with the experimental ethanol sensing behavior of the sensor in the concentration range of 90 to 630 ppm at 300 K.