2015 年 40 巻 1 号 p. 69-72
Hydrogen response characteristics of Pt/Ti film were evaluated by impedance measurement. The sensitivity of Pt/Ti film as a function of hydrogen concentration was measured by DC resistance. According to decrements of thickness, the resistivity change ratio increased. However, the response time to hydrogen gas was insufficient at room temperature, and therefore, pulsed heating was conducted to speed up the response time with low power consumption. The effect of these results of thickness dependence and the pulsed heating suggests the hydrogen response mechanism is based on the surface reaction. Therefore, AC impedance measurement was conducted to analyze the conduction mechanism of ultrathin film. As a result, Pt/Ti film is assumed to be a parallel RC circuit due to the surface roughness. In addition, both resistance and capacitance were changed and frequency dependence was observed, when exposed to hydrogen, by the AC impedance measurement. From the result of measurement and calculation, the capacitance changes occurred in high frequency by the skin effect. The carrier and proton generated by the catalytic reaction of hydrogen were thought to exist near the surface.
