Capacitive humidity sensing properties of CdS/ZnO sesame-seed-candy structure grown on silicon nanoporous pillar array

Utilizing silicon nanoporous pillar array (Si-NPA) as substrate, a kind of CdS/ZnO sesame-seed-candy structure was prepared by successively growing ZnO nanorods and CdS nanograins via chemical vapor deposition and successive ion layer adsorption reaction method, respectively. The capacitive humidity sensing properties of CdS/ZnO/Si-NPA were studied by constructing coplanar interdigital electrodes. With the relative humidity (RH) increasing from 11% to 95%, a capacitance response over 201,530% was achieved, which indicates that CdS/ZnO/Si-NPA is highly sensitive to humidity. The response and the recovery times were determined to be ∼110 s and 32 s, respectively, with a maximum hysteresis being ∼2.67% at 75% RH. The high humidity sensitivity of CdS/ZnO/Si-NPA is attributed to the enlarged specific surface area induced by its unique nanostructure, while the short response/recovery times and the small hysteresis were due to the channel network brought by Si-NPA. These results indicate that CdS/ZnO/Si-NPA might be an ideal material system for fabricating high-performance humidity sensors. A nanosystem composed of CdS/ZnO sesame-seed-candy structure and the underlying Si-NPA substrate was prepared and its humidity-sensing properties were studied. Recur to the unique hierarchical nanostructure, humidity-sensing properties of high sensitivity, short response/recovery times and small hysteresis were obtained. CdS/ZnO/Si-NPA might be an ideal material for humidity detection. [Display omitted] •A CdS/ZnO sesame-seed-candy structure is grown on silicon nanoporous pillar array.•CdS/ZnO/Si-NPA is highly sensitive to humidity.•The hysteresis of CdS/ZnO/Si-NPA is small and the response time is short.•The performance is due to the unique hierarchical structure of CdS/ZnO/Si-NPA.