Defect‐Engineered ZnO Nanowire Arrays for Flexible Room‐Temperature Hydrogen Sensors

ABSTRACT

We report a scalable fabrication strategy combining photolithographic patterning with chemical bath deposition (CBD) to produce ordered ZnO nanowire arrays on flexible polyimides for room‐temperature hydrogen sensing. Lithographically defined regions enable spatially controlled nanowire growth, while a tungsten‐based metallic glass buffer layer improves adhesion and mechanical stability of the sensing architecture. Systematic investigation of CBD conditions reveals that growth duration and solution chemistry strongly influence nanowire defect density and electronic transport behavior. Real‐time pH monitoring during growth provides insight into defect formation, where higher pH conditions promote defect‐rich surfaces exhibiting p‐type‐like sensing behavior, whereas extended growth at lower pH yields stable n‐type conductivity. Advanced TEM structural and spectroscopic analyses confirm the presence of oxygen vacancy‐rich surface layers (∼2–5 nm) that dominate surface charge transfer during gas adsorption. The optimized flexible sensor exhibits excellent room‐temperature hydrogen detection with responses of 241% at 500 ppm and 112.9% at 1 ppm H ₂ , along with preferential H ₂ response over the tested interfering gases under room‐temperature conditions, and stable operation under repeated bending. These findings establish a direct correlation between growth chemistry, defect structure, and sensing behavior in ZnO nanowire arrays and provide a scalable approach for integrating defect‐engineered oxide nanostructures into flexible gas sensors.