Optical and electrochemical studies of thiacalix[4]arene film supported on Si/SiO 2 for ion-sensitive sensor M.B. Ali a,b, * , A. Abdelghani b , H.B. Ouada a , N. Jaffrezic-Renault c , R. Lamartine d a Institut Supe ´rieur des Sciences Applique ´es et de Technologie, 4003 Sousse, Tunisia b Unite ´ de Recherche de Physique de Semiconducteurs, IPEST, la Marsa, 2070 Tunis, Tunisia c Inge ´nierie et Fonctionnalisation des Surfaces, UMR CNRS 5621, Ecole Centrale de Lyon, BP 163, 69131 Ecully ce ´dex, France d Laboratoire de chimie Industrielle, CNRS UPRES A-5078, Universite ´ Claude Bernard Lyon I, 43 Bd du 11 Novembre 1918, 69622 Villeurbanne ce ´dex, France Abstract The present work is motivated by the development of ion-sensitive sensors (suited for aqueous medium) based on functional supported thin film as sensitive membrane. Thin thiacalix[4]arene films was deposited using the technique of thermal evaporation under vacuum to fabricate chemical ion-sensitive field effect transistor (ISFET) microsensors. The aim is to characterize thiacalix[4]arene thin film (morphology, chemical composition) and its optical and electrical properties before and after detection of copper(II) ions. D 2002 Elsevier Science B.V. All rights reserved. Keywords: Thiacalix[4]arene; Impedance spectroscopy; Ellipsometry; XPS; Sensor 1. Introduction The selective measurements of ion activities in aqueous solutions by potentiometric devices like ion-selective elec- trodes (ISEs) and chemically modified field effect transistor is nowadays well established. Since the introduction of the ion-sensitive field effect transistor (ISFET) [1], much atten- tion has been given to improve the sensitivity and the selectivity of these devices. To render this structure iono- sensitive, it is necessary to functionalize it with sensing membrane [2]. The physicochemical properties of the chemical sensors are based on selective recognition of the sensing ionophore for guest species. A variety of organic supramolecules and polymeric compounds have been used as sensitive membrane for ion detection [3,4]. In particular, calix[n]arene macrocyclic molecules are able to recognise ions and organic molecules according to a key–lock inter- action mechanism [5]. Recently, ISFETs sensitivity to heavy metal ions such as silver, lead, and copper (II) have been fabricated from various derivated calix[4]arene [6]. In this respect, the newly prepared thiacalix[4]arene [7,8] repre- sents very promising molecules as sensing ionophore for ion detection. The thiacalix[4]arene (TCA) is composed of benzene rings linked via sulfide bridges, which themselves can make host – guest complexation with metallic cations. The related calix[4]arene has poor affinity towards transition metal ions (M 2+ ), whereas TCA is an excellent extractant for these metallic cations [9]. The aim of the present work is to characterize thiaca- lix[4]arene thin film (morphology, chemical composition) and its optical and electrical properties before and after detection of copper(II) ions. 2. Experimental 2.1. Preparation of samples 2.1.1. Synthesis of the sensitive molecules The thiacalix[4]arene was synthesised in the Laboratoire de Chimie Industrielle of the Claude Bernard University (Lyon, France) in a typical procedure given by Ref. [7]. 2.1.2. Deposition of thin thiacalix[4]arene film The sensitive films of thiacalix[4]arene used to function- alize the surface of Si/SiO 2 structures was deposited by thermal evaporation under secondary vacuum of 10  6 Torr. 0928-4931/02/$ - see front matter D 2002 Elsevier Science B.V. All rights reserved. PII:S0928-4931(02)00063-2 * Corresponding author. Institut Supe ´rieur des Sciences Applique ´es et de Technologie, 4003 Sousse, Tunisia. Tel.: +216-7-3332656; fax: +216-7- 3332658. E-mail address: mounirbenali@yahoo.com (M.B. Ali). www.elsevier.com/locate/msec Materials Science and Engineering C 21 (2002) 29 – 34