Sensors and Actuators B 221 (2015) 104–112 Contents lists available at ScienceDirect Sensors and Actuators B: Chemical jo u r nal homep age: www.elsevier.com/locate/snb Facile integration of ordered nanowires in functional devices Jordi Guilera a , Cristian Fàbrega a,b , Olga Casals b , Francisco Hernández-Ramírez a,b , Shuangzhou Wang c , Sanjay Mathur c , Florian Udrea d,e , Andrea De Luca d , S. Zeeshan Ali e , Albert Romano-Rodríguez b , J. Daniel Prades b,∗ , Joan R. Morante a,b a IREC, Catalonia Institute for Energy Research, San Adrià de Besòs, Spain b Departament d’Electrònica and Institute of Nanoscience and Nanotechnology (IN 2 UB), Universitat de Barcelona, Barcelona, Spain c Institute of Inorganic Chemistry, University of Cologne, Cologne, Germany d Engineering Department University of Cambridge, Cambridge, United Kingdom e Cambridge CMOS Sensors Ltd, Cambridge, United Kingdom a r t i c l e i n f o Article history: Received 24 April 2015 Received in revised form 4 June 2015 Accepted 6 June 2015 Available online 25 June 2015 Keywords: Nanowire Nanofabrication Devices Electrodes Dielectrophoresis Gas sensor Photodetector Field-effect device Low cost integration a b s t r a c t The integration of one-dimensional (1D) nanostructures of non-industry-standard semiconductors in functional devices following bottom-up approaches is still an open challenge that hampers the exploita- tion of all their potential. Here, we present a simple approach to integrate metal oxide nanowires in electronic devices based on controlled dielectrophoretic positioning together with proof of concept devices that corroborate their functionality. The method is flexible enough to manipulate nanowires of different sizes and compositions exclusively using macroscopic solution-based techniques in conven- tional electrode designs. Our results show that fully functional devices, which display all the advantages of single-nanowire gas sensors, photodetectors, and even field-effect transistors, are thus obtained right after a direct assembly step without subsequent metallization processing. This paves the way to low cost, high throughput manufacturing of general-purpose electronic devices based on non-conventional and high quality 1D nanostructures driving up many options for high performance and new low energy consumption devices. © 2015 Elsevier B.V. All rights reserved. 1. Introduction One-dimensional (1D) nanostructures offer a convenient path for the synthesis of high-quality, almost defect free, crystals of non- industry-standard semiconductor materials, such as metal oxides (MOX) [1,2]. However, the integration of these materials in func- tional devices, with the necessary degree of order and complexity, is an open challenge that still hampers the exploitation of their poten- tial in full [2,3]. Current bottom-up approaches rely on a complex combination of positioning methods (e.g. nanomanipulation, self- assembly, di/electrophoresis, etc.) [3–5], and connecting methods (e.g. UV, electron/ion beam, soft lithographies) [6–8]. This strat- egy is however far from reconciling technical requisites with cost requirements of the industry. A decade of research efforts shows that the most advanta- geous nanodevice configuration requires either a single (or a few) nanowires running parallel between two electrodes [9] to thus ∗ Corresponding authors. Tel.: +34 934039159. E-mail address: dprades@el.ub.edu (J.D. Prades). build up a well-defined conduction channel to be easily modulated by external stimuli (e.g. chemical or biological agents [10,11], light or radiation [12], external electric fields [13,14], etc.). This means explicitly avoiding random wire-to-wire conduction paths which inevitably appear in devices based on randomly oriented mats of 1D nanostructures [15]. In the particular case of metal oxide nanowire-devices, this con- figuration has successfully led to a high number of applications and proof-of-concept prototypes, proving their interest in high temperature and power electronics, in which highly miniaturized field-effect transistors of wide-band gap semiconductor are sought after [16–18]. On the one hand, and regarding gas detection applications, nanowire-based metal oxide sensors [19,20] display important advantages only accessible in ordered configurations [15]. Firstly, the large surface-to-volume ratio of nano-sized materials provides a systematic way to increase the influence of surface phenomena, such as the response to gases [21]. Secondly, nanowires are typically enclosed by well-terminated surfaces in well-defined crystal orien- tations, offering a reduced set of interaction sites with gases that render better reaction control, and in general good signal stability http://dx.doi.org/10.1016/j.snb.2015.06.069 0925-4005/© 2015 Elsevier B.V. All rights reserved.