Development of a Miniaturized Gas Ionization Sensor for Harsh Environments by Using Polyimide Spacer T. Walewyns a , G. Scheen a , E. Tooten a , P. Dupuis a , and L. A. Francis a a Sensors, Microsystems and Actuators Laboratory of Louvain (SMALL), Electrical Engineering Department (ELEN), Institute for Information and Communication Technologies, Electronics and Applied Mathematics (ICTEAM), Université catholique de Louvain (UCL), Louvain-la-Neuve, Belgium Gas sensing can be performed by fingerprinting their field ionization characteristics. This paper presents the development of a miniaturized ionization sensor using ion-track etched polyimide as structural layer and template for Ni nanowires synthesis. The device consists in two parallel plate electrodes with gaps varying from 5 to 12 µm. The nanowires impact on breakdown voltage has been analyzed during first electrical characterizations and I-V curves measurements. For a 5.5 µm-gap, breakdown voltage is reduced from 320 to 80 V with a corresponding current at least three order of magnitude lower. Using the sensor in harsh environments such as space applications is also discussed. Miniaturized ionization sensors are powerful candidates as integrated universal gas sensor based on pattern recognition for environmental monitoring. Such a system should be easily integrated in picosatellites such as CubeSats dedicated to the physical analysis of low thermosphere composition. 1. Introduction Nowadays, miniaturized gas sensors are increasingly used in medical or environmental monitoring, heavy industry, logistic and defense. Current portable devices with catalyst-based electrochemical cells show limited sensitivity, low durability and selectivity issues. Furthermore, solid-state resistive materials, more sensitive, require elevated local working temperatures. To overcome these sensibility and selectivity issues, the chemical analysis of gaseous compounds can be performed by fingerprinting their field ionization [1, 2, 3, 4, 5]. For a specific gas or for a gas mixture trapped between two metal electrodes, the current flowing through the ionized gas as a function of the applied voltage results in a unique fingerprint at known humidity level, and pressure level in case of mixture. In order to enhance electric field and reduce the working voltage, sharp nanotips, such as multi- walled carbon nanotubes (MWCNTs) [1, 2], metallic [3] or semiconductor [4] nanowires, are incorporated on the bottom electrode (cathode or anode, depending on the device configuration). However, carbon nanotubes show a low stability compared to nanowires [5]. Sadeghian et al. [3] have obtained threshold field-ionization voltages of 0.2 to 9 V (depending on the measured gas) by incorporating whisker-covered gold nanowires on the cathode. Recently, they used whiskered silicon nanowires in a tree structure to further increase device performance [4]. With such approach, sensors with high sensitivity, high selectivity, long durability and (ultra)-low-power operation (P ≤ 1 µW with ionization ECS Transactions, 35 (30) 119-128 (2011) 10.1149/1.3653930 ©The Electrochemical Society 119 Downloaded 15 Oct 2011 to 91.178.103.144. Redistribution subject to ECS license or copyright; see http://www.ecsdl.org/terms_use.jsp