Experimental verification of theoretical analysis of Pd/porous-GaAs as a hydrogen sensor

Abstract

The Pd/porous GaAs Schottky sensor reveals high potential for hydrogen detection at room temperature (Salehi et al 2006 Sensors Actuators B 113 419–27). The Pd/porous GaAs Schottky sensor fabricated in this study exhibited a considerable increase in sensitivity three times that of the non-porous sensor submitted to 500 ppm hydrogen gas at room temperature. The theoretical analysis presented here proves that the sensitivity of the porous sample should be more than that in the non-porous sample and this higher sensitivity refers to more hydrogen adsorption at the interface of the contact. The increased sensitivity coefficient in the porous sensor is related to the morphology of the surface and is a function of two parameters: increase in surface area and density of cavities between pore walls (number of pores which is important in catalyzers). We believe that porosity, in addition to increased surface area and adsorption site, causes an additional increase in sensitivity. Moreover, the response time of the sensors was modelled for non-porous and porous samples exposed to hydrogen gas. As analytical predictions were experimentally verified, the porous sample exhibited a rise time comparable to the non-porous sample but in spite of a low rise time the recovery time of the porous sample is much larger (about four times) than that of the non-porous sample.