Photothermal Electrostatics of the Pd-Polyvinylidene Fluoride Photopyroelectric Hydrogen Gas Sensor

Abstract

A detailed photothermal electrostatic consideration of the Pd-pyroelectric junction H-2 sensor is presented. Experimental evidence is in agreement with the fundamental features of the theory, which supports two possible mechanisms of ac-mode device operation: pyroelectric coefficient dependence on the hydrogenic dipole-induced charge density at the Pd-insulator polyvinylidene fluoride interface, and thermal-wave modulation of the hydrogen-concentration-dependent Pd work function. The dominant operating mechanism is found to depend on the experimental conditions. The concept of image dipole thermostatistical vibration and libration in the pyroelectric matrix is further successfully used to explain the temperature dependence of the photopyroelectric signal in support of the former above-mentioned mechanism.