Enhanced response and recovery observed in CNTs gas sensor using ZnO/HfO2 bilayer memristor heater

Abstract

In carbon nanotubes (CNTs) based gas sensors, external energy sources are used to enhance the response and recovery characteristics, However, they have significant energy consumption and are constrained by size limitations. In this work, to solve them, we propose a ZnO/HfO₂ bilayer–memristor heater (MH) embedded CNTs gas sensor. Firstly, when tuning the thickness of ZnO in the MH, we observed a thickness dependency in the response characteristic, which can be explained by the variation in the gap of the ruptured conduction filament (CF). As a result, the 70 nm–ZnO MH, which had the longest gap between the ruptured CF and the CNTs layer, demonstrated the highest response of 58.3%. This response is 54.1% higher than that of the conventional CNTs gas sensor. In addition, in a pulse recovery study, we observed that the MH–embedded CNTs gas sensor returned to its initial state within only 1 ms after gas detection, which is 35ⅹ10⁵ times faster than a conventional CNTs sensor. These results indicate that the heating caused by the MH can effectively raise the temperature of the insulator near its surface, meaning that MH can be a good candidate as a heater in the microscale gas sensors.