Effect of the deposition method and substrate on an ultra-stable CoV2O6 hydrogen gas sensor, operating at room temperature

Abstract

The constantly increasing demand for flexible, reliable and stable gas sensors, operating at room temperature, which would be integrated with present electronic circuits for real life applications is a true fact. In the present work, the gas sensing properties of bimetallic cobalt‑vanadium-oxide system (CoV2O6) under the effect of deposition method (spin coating, direct ink writing and drop-casting) as well as the type of substrate (glass, flexible PET), at room temperature were examined. The surface morphology as well as the film thickness of the sensing material were investigated by Scanning Electron Microscopy. The spin-coated sensor on glass substrate exhibited the higher response (65.2%) towards 1000 ppm H2 at room temperature, compared to those that were deposited with the other methods, showing a response and recovery time of 94 s and 74 s, respectively. The CoV2O6 flexible PET sensor exhibited a response of 36.6% against 1000 ppm H2, at room temperature, with a response and recovery time of 120 s and 80 s, respectively. In addition, both operation under bending conditions at 180o and the reliability, in terms of repeatability of signal and stability after 1 year, were studied for the CoV2O6 flexible PET sensor. Finally, a sensing mechanism is proposed taking into account the thickness and architecture of the films as well as film variations and imperfections of the active sensing surface, such as micro-cracks, edges and pores. These parameters play a dominant role on the gas sensing performance far greater than that of the substrate or the metal electrodes. The realization of a CoV2O6 flexible sensor demonstrates its potential for real-life applications.