Humidity Sensing Properties of Plasma Polymerized Organic Thin Films

Various polymerized organic thin films were deposited on a comb-shaped electrode by using a capacitive-coupled gas flow type plasma polymerization apparatus. The humidity sensing characteristics of these thin films were measured by means of changes in electrostatic capacitance within the frequency and humidity range of 60Hz -100kHz and 20-90%RH, respectively.The capacitances of these thin film were increased with increasing relative humidity. And the increments of the capacitance grow larger with a lower discharge power and a shorter polymerization time. The linearity and increment of the capacitance change became apparent with the lower frequency of input power to thin films during the capacitance measurements.