Table 8.
Different types of zinc oxide-based humidity sensors and their synthesis methods.
| Sensor Material | Method | Response Time (s) | Recovery Time (s) | Hysteresis (%) | Ref. |
|---|---|---|---|---|---|
| Flower-like ZnO nanorods on a ceramic substrate with silver-palladium (Ag–Pd) interdigital electrodes | Screen-printing | 5 | 10 | 2 | [158] |
| KCl-doped ZnO nanofibers | Electrospinning | 2 | 1 | - | [159] |
| ZnO nanofibers and LiCl-doped ZnO composite fibers on ceramic substrates with carbon interdigital electrodes | Screen-printing | 3 | 6 | 2 | [160] |
| KCl-doped Cu–Zn/CuO–ZnO (KCZ/CZN) nanoparticles | Wire electrical explosion (WEE) | 40 | 50 | 4 | [161] |
| High pure ZnO colloidal nanocrystal clusters (CNCs) | Modified hydrolyzation | 110 | 80 | - | [162] |
| Nanocrystalline zinc tungstate (ZnWO4) (nanoparticles, nanorods) | Precipitation or hydrothermal | 3 | 50 | 5.5 | [163] |
| ZnO and In2O3 thin films on SiO2/Si substrates with interdigitated Pt signal electrodes | Radio-frequency sputtering | 15 | 40 | 4 (for ZIZ) | [164] |
| Mn-doped ZnO nanopowders | Sol-gel | 6 | 20 | 4.36 (for 6 at % Mn doping) | [165] |
| ZnO nanorods (Capacitive type) | Thermal decomposition and Dielectrophoretically manipulation for deposition on the micromachined electrodes pairs | 70 | 20 | - | [166] |
| Porous zinc aluminate (ZnAl2O4) spinel nanorods | Homogeneous co-precipitation approach followed by a heat treatment at 900 °C | 15 | 30 | 2 | [167] |
| ZnO colloid spheres (coated on quartz crystal microbalance, QCM) | Self-assembly | 38 | 18 | - | [168] |
| A-plane ZnOnanotip on R-plane sapphire substrate | Metal organic chemical vapor deposition (MOCVD) | 3 | 12 | 1.9 | [169] |
| ZnO on a template of silicon nanoporous pillar array (Si-NPA), a regular array of ZnO cauliflowers (Capacitive type) | Chemical vapor deposition (CVD) | 20 | 3 | 4.16 | [170] |