Synthesis of ZnO thin films and their application as humidity sensors

Humidity sensors were fabricated using ZnO thin films synthesized on a Si wafer substrate. The ZnO thin films were grown via a vapor solid (VS) approach at temperatures ranging from 400 to 700 °C. Experiments were executed to observe the relationships between the relative humidity (RH) and resistance of these devices fabricated under various VS temperatures. Experimental results show that the ZnO thin films grown at a temperature of 700 °C using the VS approach exhibits an optimum sensitivity to humidity. The measured sensor resistance ranges from 495 × 10⁶ to 46 × 10³ Ω for RH ranging from 11 to 95 % at room temperature. The variance of sensor resistance exceeds 10⁴ times, indicating that the proposed method can produce a highly sensitive humidity sensor.