Model validation of a mercury sensor, based on the resistivity variation of a thin gold film

Abstract

Nowadays, the awareness of the importance of mercury as a global pollutant increases the need for new tools helping support citizens' health safeguard. With this in mind, the authors developed a microfabricated sensor to monitor elemental gaseous mercury (Hg 0) in the air, and they presented it in a previous work. A deep understanding of the physical phenomena concerning the processes involved was necessary to improve the performance and to develop an "optimised sensor". This paper presents a simple physical model, developed to quantitatively estimate the sensitivity of a mercury sensor. The sensor is based on the resistivity variation induced by the adsorption of mercury onto a thin gold film. The model provided the design criteria for a new version of the mercury sensor. The paper describes the model validation, which was carried out through a series of experiments on new sensors, as well as the new design, microfabrication process, and technical features of the mercury sensor. The sensor consists of a miniaturized system, which includes the sensing element, the electrical routes, and a digital temperature sensor integrated onto a small SIM-card-shape substrate. Conventional IC technologies and materials were used throughout the sensor fabrication process, in order to produce a low-cost microsystem, which could be used as a disposable sensor