Sensors and Actuators B 118 (2006) 149–155 PLD-prepared cadmium sensors based on chalcogenide glasses—ISFET, LAPS and ISE semiconductor structures J.P. Kloock a,b , L. Moreno c , A. Bratov c , S. Huachupoma a,b , J. Xu a,b , T. Wagner a,b , T. Yoshinobu d , Y. Ermolenko e , Y.G. Vlasov e , M.J. Sch ¨ oning a,b,∗ a Aachen University of Applied Sciences, J¨ ulich Campus, Laboratory for Chemical Sensors and Biosensors, Ginsterweg 1, 52428 J¨ ulich, Germany b Research Centre J¨ ulich GmbH, Institute of Thin Films and Interfaces (ISG-2), 52425 J¨ ulich, Germany c Centre Nacional de Microelectr´ onica (CNM), CSIC, Campus UAB, 08193 Bellaterra, Spain d Tohoku University, Department of Electronic Engineering, 6-6-05 Aramaki Aza Aoba, Aoba-ku, Sendai, Miyagi 980-8579, Japan e St. Petersburg State University, Faculty of Chemistry, 199034 St. Petersburg, Russia Available online 16 May 2006 Abstract In this work, ion-selective field-effect transistors (ISFET), light-addressable potentiometric sensors (LAPS) and miniaturised ion-selective electrodes (ISE) are investigated for the detection of cadmium ions in aqueous solutions for future multi-sensor applications. The sensor membranes are based on a chalcogenide glass material (CdSAgIAs 2 S 3 ) that has been deposited as thin film onto different transducer structures by means of the pulsed laser deposition (PLD) technique. The prepared thin films were physically characterised by means of optical microscopy, Rutherford backscattering spectrometry (RBS) and scanning electron microscopy (SEM). The electrochemical characterisation was done by means of ion- selective potentiometry (ISE), current/voltage, constant current (LAPS) and constant-charge mode (ISFET) measurements. © 2006 Elsevier B.V. All rights reserved. Keywords: Heavy metal detection; Chalcogenide glasses; Pulsed laser deposition; ISE; ISFET; LAPS 1. Introduction The detection of heavy metal ions in aqueous solutions rep- resents one important measurement task in the fields of environ- mental and industrial water analysis. For practical applications, devices for on-site measurements can be recommended, but the major problem is still the lack of suitable sensor membranes. One approach to realise sensor membranes with high chemical stability offer ion-selective electrodes (ISE) based on chalco- genide glass materials. Since more than 20 years, chalcogenide glass bulk materials for the detection of various heavy metal ions in aqueous solutions are well investigated by Vlasov and co-workers [1–4]. In addition, a recently published review arti- cle by Vassilev and Boycheva gives a survey on chemical sensors with chalcogenide glassy membranes [5]. Due to the good stability in liquid media in comparison to their crystalline counterparts, their high long-term stability in operation and their low detection limit, chalcogenide glasses ∗ Corresponding author. Tel.: +49 2461 993215; fax: +49 2461 993235. E-mail address: m.j.schoening@fz-juelich.de (M.J. Sch ¨ oning). are useful to solve the problems, described above. Moreover, nowadays the “on-line” detection of several ions becomes more and more important. For the realisation and fabrication of such devices, methods of silicon planar technology are preferred: Dif- ferent transducer structures such as ISFETs, LAPS or ISE can be prepared by means of these methods. However, there is still a lack of preparation of chalcogenide glass sensor membranes compatible to the well-established thin film methods of semicon- ductor industry. The main difficulty is that standard methods of thin film deposition, like electron-beam evaporation or various methods of sputtering, do not permit the stoichiometric transfer of a complex target material, like multicomponent chalcogenide glasses (which is required for a proper functioning of these thin film sensor membranes as chemical sensor). Recently, the authors introduced the PLD process [6–14] as a novel tool for the preparation of chalcogenide glasses in the thin film state. The advantages of the PLD process are the sto- ichiometric transfer from the original target material to a given substrate, the easy set-up and short process times and even the process compatibility to semiconductor fabrication steps. As a first approach for the miniaturisation of chalcogenide glass sensors, ISEs for the detection of Pb 2+ , Cd 2+ , Cu 2+ and Tl + 0925-4005/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.snb.2006.04.018