Micro Humidity Sensor with High Sensitivity and Quick Response/Recovery Based on ZnO/TiO_(2) Composite Nanofibers

ZnO/TiO_(2) composite nanofibers are synthesized by an electrospinning method and characterized by x-ray diffraction,scanning electron microscopy,and transmission electron microscopy.A micro humidity sensor is fabricated by spinning the precursors of these nanofibers on a ceramic substrate with Ag-Pd interdigitated electrodes.Humidity sensing investigation reveals that this micro sensor offers high sensitivity and quick response/recovery at an operating frequency of 100 Hz.The corresponding impedance changes more than four orders of magnitude within the whole humidity range from 10%to 90%relative humidity(RH),and the response and recovery times are about 4 and 12 s,respectively.The maximum hysteresis is around 2%RH.The humidity sensing mechanism is also discussed based on the nanofiber structure and morphology.