Correlation of Electrode–MWCNT Intersection Area and Gas Sensing Response in Ammonia Sensor

Carbon based chemiresistive gas sensors have attracted considerable attention due to their high sensitivity, simple device structure, and compatibility with low power op eration. In this work, we systematically investigate the role o f electrode–CNT intersection area on the NH₃ sensing char acteristics of multi-walled CNT (MWCNT) gas sensors. Au electrodes with precisely controlled overlap areas were fa bricated using oxygen plasma–assisted patterning and sp ray coating deposition, while maintaining identical active s ensing regions. Morphological, structural, and chemical anal yses confirmed that plasma processing preserved the intrinsi c electrical and mechanical properties of the MWCNT films. G as sensing measurements revealed that although the active s ensing region dominates the response, the electrode–channel intersection area significantly influences sensitivity by modu lating interfacial charge injection. The response increased with intersection area but tended toward saturation, and the nor malized sensitivity peaked near 10 mm² before decreasing. These findings demonstrate that optimal sensor performance is achieved not by maximizing the intersection area, but by rationally limiting it to approximately 10 mm², providing a design g uideline for efficient CNT–metal electrode gas sensors with balanced sensitivity, power consumption, and material utilizatio n.