When Organometallic Chemistry and Metal Oxide Nanoparticles Meet Optimized Silicon-based Gas Sensor
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When organometallic chemistry and metal oxide nanoparticles meet optimized silicon based gas sensor Paméla Yoboue1, Philippe Ménini1,2, André Maisonnat3, Myrtil Kahn3, Katia Fajerwerg2,3, Bruno Chaudret3, Pierre Fau2,3 1
Laboratoire d’Analyse et d’Architecture des Systèmes, LAAS-CNRS, 7 avenue du colonel Roche, 31077 Toulouse, France 2 University of Toulouse (Toulouse III), 118 route de Narbonne, 31062 Toulouse Cedex 02, France 3 Laboratoire de Chimie de Coordination LCC-CNRS, 205 route de Narbonne, 31077 Toulouse Cedex 04, France
ABSTRACT A robust silicon gas sensor chip (platinum heater, low stress membrane) has been designed and successfully operated with various metal oxide nanoparticles synthesized by organometallic route (SnO2, ZnO) deposited by a generic ink-jet method. Micron thick layers made of nanostructured grains are obtained and the sensitivities under CO gas are presented.
INTRODUCTION The air quality control in confined places (automotive cabin, transportation and offices or working places) is getting more and more necessary in the actual pollution levels due to the growing industrial environment. Despite the intense research work in the field of new silicon sensors and sensitive elements, the need for a high accuracy and low cost metal oxide gas sensors remains a challenge. Generally, the gas sensor substrate is based on commercial alumina support which comprises sensitive layer contact electrodes and an integrated platinum heater for heating purpose [1-3]. These devices present high power consumption and are not well adapted for miniaturization. Since few years, an alternative to alumina substrate has been proposed by the microelectronics tools together with the development of micromachined silicon devices and integrated polysilicon heaters [4-6]. The generally admitted drawbacks of such silicon chip is due to the resistance drift of the polysilicon heating element upon time, and the mechanical deformation of the insulating supporting membrane on which rely the sensitive layers. All these defects can lead to the progressive lost of sensor performance upon time. We have developed a new generation of metal oxide gas sensor, based on the combination of an optimized micromachined silicon substrate and a highly sensitive nano-sized metal oxide derived from organometallic synthesis route [7, 8] A platinum heater structure insures a stable thermal property of the silicon platform, a low deformation membrane is implemented and the nanostructured sensitive layers are ink-jet deposited on the device.
EXPERIMENTAL DETAILS Silicon platform
Commercial integrated heaters on silicon platforms are generally built with n-doped (phosphorus) or p-doped (boron) polysilicon layers. The desired resistance level of the polysilicon layer is achieved by the high temperature diffusion (1000°C) of the doping elements inside the silicon grains. One of the major drawbacks of such device is linked to the progressive drift of their electrical properties upon sensor operation temperature. At a constant temperat
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