Please cite this article in press as: H. Guerin, et al., Carbon nanotube gas sensor array for multiplex analyte discrimination, Sens. Actuators B: Chem. (2014), http://dx.doi.org/10.1016/j.snb.2014.10.117 ARTICLE IN PRESS G Model SNB-17615; No. of Pages 10 Sensors and Actuators B xxx (2014) xxx–xxx Contents lists available at ScienceDirect Sensors and Actuators B: Chemical jo ur nal home page: www.elsevier.com/locate/snb Carbon nanotube gas sensor array for multiplex analyte discrimination Hoël Guerin a,∗ , Hélène Le Poche b,c , Roland Pohle d , Elizabeth Buitrago a , Montserrat Fernández-Bola ˜ nos Badía a , Jean Dijon b,c , Adrian M. Ionescu a a École Polytechnique Fédérale de Lausanne (EPFL) – Nanoelectronic Devices Laboratory (NANOLAB), ELB 335, Station 11, 1015 Lausanne, Switzerland b Univ. Grenoble Alpes, F-38000 Grenoble, France c CEA, LITEN, DTNM, F-38054 Grenoble, France d Siemens AG Corporate Technology, CT RTC SET CPS-DE, Otto-Hahn-Ring 6, 81739 München, Germany a r t i c l e i n f o Article history: Received 28 April 2014 Received in revised form 17 September 2014 Accepted 27 October 2014 Available online xxx Keywords: Carbon nanotube Gas sensor Multiplex gas discrimination Metal–nanotube interface a b s t r a c t The lack of selectivity toward a particular analyte has always been the primary concern regarding CNT- based gas sensors. For that reason, in here we present a gas discrimination strategy that focuses on the electrode–CNT junction. The junction is shown to play a key role in the sensing mechanism. Resistive gas sensors based on horizontal CNT arrays have been fabricated using various designs and different top- contacting metals: Pt, Pd and Au. Arrays of devices have been exposed to a series of gases to monitor their resistive response. It was found for our system that the sensor response does not significantly change as a function of the device design or the available CNT sensing area in between the anchoring electrodes. On the contrary, responses to gases are observed to be specific to each sensor electrode metal. Exposure of locally passivated devices (for which distinct areas have been covered) to NO 2 , H 2 and NH 3 highlights different sensing mechanisms for each gas. Multiplex gas discrimination for room temperature can be achieved by strategically choosing the right metal/CNT combination in a complete sensor system. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Discovered in 1991 by Iijima [1], carbon nanotubes (CNT) have been intensively investigated thanks to their unique electrical and mechanical properties [2,3]. CNTs are both a stiff and light material that exhibits a high Young’s modulus and good electrical conductiv- ity without electron migration issues [4]. As a consequence of these exceptional properties, CNTs have become a promising alternative for a wide range of applications in micro/nano electronics from interconnecting lines [5], field-effect transistor (FET) based logic gates [6], nano-electro-mechanical systems (NEMS) [7] to chemical sensors [8]. Since semiconducting single wall carbon nanotube (SWCNT) FETs were found to exhibit resistance variation upon exposure to NH 3 and NO 2 in the early 2000s [9], they have been widely investi- gated for gas sensing applications. Different groups have reported remarkable sensitivities of CNT-based sensors to a wide spectrum of gases such as CO x , SO x , NO x , alcohols, organic vapors (important for disease diagnosis), explosive compounds and chemical warfare ∗ Corresponding author. Tel.: +41 216937856. E-mail address: hoel.guerin@epfl.ch (H. Guerin). agents among others, with detection limits in the order of ppm or ppb [10–12]. Whereas the most common metal oxide semiconduc- tor sensing technology is currently facing power limitations, due to its high operation temperature, and scaling issues [13], CNTs exhibit many properties that are desirable for gas sensing [14]. The nanotubes are almost exclusively composed of surface atoms. The conducting channel of a CNT based sensor is therefore always in direct proximity with the gas analytes. The surface effects of gas molecules generate high responses from the CNTs. The inherent high sensitivity of the CNTs removes the need for supplementary technologies such as gas preconcentration. Thus, CNT sensors can benefit from simple device configurations for low cost, miniatur- ized sensing applications. Thanks to their p-bonds perpendicular to the CNT surface, CNTs are also electrochemically active at room temperature making them suitable for the development of a low power sensing technology [15]. However, the main drawback to the superior performances of CNT-based gas sensors is the lack of selective detection toward a particular analyte. Consequently, the risk of false alarms is high and many functionalization strategies have been developed in order to obtain a gas specific response. Methods that have yielded good results include the decoration of CNTs with different metal nanoparticles [16,17] or coating with polymers [18,19]. However, such functionalization strategies may http://dx.doi.org/10.1016/j.snb.2014.10.117 0925-4005/© 2014 Elsevier B.V. All rights reserved.