Bottom-up Fabrication of Individual SnO 2 Nanowires-based Gas Sensors on Suspended Micromembranes
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1052-DD08-02
Bottom-up Fabrication of Individual SnO2 Nanowires-based Gas Sensors on Suspended Micromembranes Albert Romano-Rodriguez1, Francisco Hernandez-Ramirez1,2, Joan Daniel Prades1, Albert Tarancon1, Olga Casals1, Roman Jimenez-Diaz1, Miguel Angel Juli1,2, Juan Ramon Morante1, Sven Barth3,4, Sanjay Mathur3,4, Andreas Helwig5, Jan Spannhake5, and Gerhard Mueller5 1 Electronics, University of Barcelona, Martí i Franquès 1, Barcelona, E-08028, Spain 2 NTEC106, S.L., Mare de Deu dels Desemparats 12 baixos, L'Hospitalet de Llobregat, E-08903, Spain 3 Chemistry, University Würzburg, Würzburg, D-97070, Germany 4 Nanocrystaline Materials and Thin Film Systems, Leibniz Institut of New Materials, Saarbruecken, D-66123, Germany 5 IW-SI Sensors, Electronics & System Integration, EADS Deutschland GmbH, Muenchen, D81663, Germany ABSTRACT Bottom – up techniques were used to obtain gas sensors based on individual SnO2 nanowires placed over microhotplates with integrated heaters. These nanowires were electrically connected to pre-patterned microelectrodes by means of Focused Ion Beam (FIB) nanofabrication methodologies. The performance of these sensors, which exhibit reproducible and stable responses, was evaluated as a function of different gas atmospheres and power dissipated by the heater, demonstrating that this technological approach could be used to develop functional devices based on nanomaterials. INTRODUCTION The new properties of nanomaterials with respect to bulk materials have attracted great research interest because of their potential applications in functional devices [1]. Although great advances have been realized in the synthesis and characterization of nanomaterial’s fundamental properties, the fabrication of reliable and reproducible devices based on these nanomaterials is still rare due to the difficulties in studying them [2]. In this work, bottom – up techniques were used to fabricate sensors based on individual SnO2 nanowires placed over microhotplates with heaters, which allows a fast modulation of their working temperature and their sensing characteristics. This approach is based on previous work in which similar nanowires have been connectged to standard photolighographically defined microelectodees on oxidized silicon wafers [3]. The stability of some of these devices was evaluated as a function of the operating time and the applied current, showing good performance for weeks and with currents below I = 100 nA. At higher currents, self heating related problems, such as degradation of the electrical contacts and irreversible damage of the nanowires, were observed.
EXPERIMENT Monocrystalline SnO2 nanowires were synthesized by chemical vapor deposition following a process explained previously [4]. These nanowires were grown as single-crystalls with dislocation-free bodies. Their main growth direction was [100] with interplanar spacing according to the rutile structure of SnO2. The length and radii of these nanowires varied between 2 and 7 microns, and between 30 and 70 nm respectively. The grown nan
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