Crystallographic Nanojunctions of Bismuth Ferrite for Unconventional Detection of Carbon Monoxide

The present work reported, for the very first time, a crystallographic junction formed of (002) and (110) oriented crystals of bismuth ferrite (BFO) for ultrasensitive carbon monoxide (CO) detection. Growth orientation and crystallinity of the solution-processed BFO were controlled by varying calcination times. The sensor demonstrated a maximum response of six times for 30 ppm of CO, with response and recovery times of 149 and 226 s, respectively, with a significant specificity over other chemically compatible species. The device showed excellent stability when tested continuously for a period of 150 days with a maximum response deviation of ±0.35 times for 30 ppm of CO. The sensitivity of the sensor significantly increased in comparison to other polycrystalline variants with less or no junctions. In order to understand the effect of crystallographic junctions on sensing performance, an analytical model was put forward. The proposed model established the dependency of the sensor response pattern on the carrier diffusion coefficient ( D g ) of the exposed gas and the ease of carrier diffusion through the gas–surface junction, which is controlled by the junction bias and the drift current. Hence, the proposed junction-based sensor provides additional control over the sensor efficiency in comparison to its resistive counterparts, thereby significantly improving the device performance without significantly complicating the device.