Abnormal p‐type Gas‐Sensing Response to Ether in Co‐ZnO Nanocomposite Film and Its Significant Room‐Temperature Magnetoresistance

Abstract As a remarkable gas‐sensing material, ZnO is limited by the gas selectivity of its indiscriminate response to multiple gases. Herein, abnormal p‐type responses to ether but n‐type responses to othervolatile organic compoundsare observed in Co‐ZnO nanocomposite films. It should be attributed to the p‐type inversion region at the ZnO particle interface, on which ether tends to selectively adsorb. By controlling Co content, a nanoflower structure is realized, which significantly increases the adsorption sites and enhances the abnormal p‐type response to eight times that of ZnO film. Dual‐mode output based on chemiresistive and magnetoresistance responses offers another way to improve gas selectivity. To this point, a dual‐response structure of Co‐ZnO nanocomposite granular film is constructed with superficial Co₃O₄‐ZnO p‐n heterojunction and internal Co‐ZnO superparamagnetic conduction path. The high saturation magnetization of 2990 Gs is realized in Co‐ZnO film with 26 at.% Co. P‐type gas‐sensing resistance variation of 12% and room‐temperature magnetoresistance of ‐7% are simultaneously achieved.