Isolde Simon

Micromachined metal oxide gas sensors: opportunities to improve sensor performance

Abstract This review deals with gas sensors combining a metal oxide based sensing layer and a substrate realized by using micromachining. It starts by giving an overview of the design principles and technology involved in the fabrication of micromachined substrates examining thermal and mechanical aspects. Both kinds of micromachined substrates, closed-membrane-type and the suspended-membrane-type, are discussed. The deposition of the sensing layer is complicated by the mechanical fragility of the micromachined substrates. Different approaches used for the formation of the sensing layer such as thin film and thick film deposition techniques are reviewed. Finally, the gas sensing function of the sensitive layer is analyzed and various ways for extracting the information are presented with respect to the improvement of sensor performance brought by this new approach.

Thermal and Gas-Sensing Properties of a Micromachined Thermal Conductivity Sensor

This work describes the design of a micromachined thermal conductivity sensor and its characterization with respect to thermal and gas-sensing properties. Optimization of sensitivity, power consumption and thermal response can be achieved by variation of heater and membrane geometry. Theoretical and experimental results of different sensor designs are presented in this contribution.