Nano Zinc Oxide-Based Impedimetric Humidity Sensor

The demand for humidity sensors has increased significantly due to their essential role in environmental monitoring and industrial process control. Precise humidity regulation is critical in applications such as climate control systems, household appliances, video recording equipment, storage facilities, paper manufacturing, food processing, tobacco handling, textile industries, and moisture-sensitive integrated circuit (IC) packaging. In the semiconductor industry, particularly during advanced wafer fabrication, continuous monitoring of moisture levels is indispensable to ensure device reliability and performance. In addition, humidity sensors are widely used in domestic environments for intelligent building management, automated microwave cooking systems, and smart laundry control, as well as in various medical and industrial applications. The main objective of the present study is to develop a humidity sensor based on nanostructured ZnO using the AC impedance technique. Three different ZnO nanomaterials were investigated: (i) a sputtered ZnO thin film with a thickness of approximately 100 nm, (ii) a commercially available ZnO powder with particle sizes below 100 nm, and (iii) an annealed form of the commercial ZnO powder. A detailed characterization of the samples was carried out employing X-ray diffraction (XRD), atomic force microscopy (AFM), UV–visible spectroscopy, Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, and photoluminescence (PL) spectroscopy to assess their structural, morphological, and optical features.