Oxidised porous silicon samples prepared from highly and weakly doped p-type silicon substrates, have been functionalised with calix[4]arene (CA) molecules. They have been used for sodium detection as electrolyte/insulator/silicon (EIS) structures. An over Nernstian behaviour was observed and correlated with physical parameters of porous silicon samples (porosity, resistivity). A generalised Nernstian equation was proposed in order to describe this property. CA functionalised EIS structures based on porous silicon present higher lifetime compared to flat structures.

This paper shows the possibility of using oxidised porous silicon (PS) as a transducer material for ion-sensor applications. It aims to study the over-Nernstian behaviour of the porous electrodes towards the concentration of cations in contact. The dependence of the sensitivity on the porosity of the samples prepared from highly doped substrates has been studied. Maximal values of over-Nernstian sensitivities around 240 mV/pNa and ∼92 mV/pCu, corresponding to a PS-layer porosity of about 65%, obtained respectively from p− and p+ silicon substrates, have been registered. Furthermore, the effect of the porous nanostructure morphology has been studied, by preparing PS samples from weakly doped wafers. The porous-silicon-based sensor behaviour for different PS-layer thicknesses has also been experimentally investigated. According to these results, a physical model has been proposed to explain the mechanisms which govern the charge-carrier transfer from one side to the other of the functionalised oxide layer, and leads to the over-Nernstian adsorption of the cationic species at the electrolyte/SiO2 interface. Afterwards, the Nernst relation has been generalised accordingly, on one hand, to the previous experimental results, and on the other hand, to the results obtained about the ion-valency and the electrolyte-temperature effects on the sensor responses.

This paper shows the possibility to use the oxidized porous silicon (PS) as a transducer material for ion sensor application. It aims to study the over Nernstian behavior of the porous material towards the concentration of sodium ions in contact. We have studied the dependence of the PS sensitivity on the porosity of the samples, which are prepared from a lightly doped silicon substrate. Then, we have presented a model to explain the mechanism of the ionic species adsorption at the electrolyte/SiO2 interface, and to interpret the observed large sensitivity against the different concentrations of the cations. The reproducibility of the sensor response and its lifetime were satisfactory for a frequent use.

Large size odd-numbered calixarenes were used for the first time as ionophoric agents for the functionalization of ISFET microsensors and EIS structures through thermal evaporation process. Both calixarenes have shown a nernstian sensitivity over three decades towards only copper (II) activities. Very low selectivity coefficients were observed for K+ and Ca2+ whereas Cd2+ and Pb2+ (less than 10−3) can be considered as interfering ions. Lifetime of around three months for the microsensors were obtained.

In this work, we present experimental results about electrolyte–insulator–semiconductor (EIS)-type sensors based on evaporated p-tert-butylcalix[4]arene sensitive thin films devoted to sodium detection. Several calixarene films of different thicknesses (10–1000 nm) were studied and a significant decay of their detection ability was pointed out for thick samples. To investigate the presence of sodium encaged in the sensitive receptors, during the contact with the electrolyte, two surface analytical methods were used, namely, Rutherford backscattering spectroscopy (RBS) and low energy electron induced X-ray spectrometry (LEEIXS). Both methods show that sodium is incorporated within the membrane and that its surface concentration decreases as the calixarene film thickness increases, due to the growth of microcrystallites in the thickest films as pointed out by atomic force microscopy (AFM) observations.

We have recently synthesised a random poly(meta/para phenylene) (PMPP) by an electrochemical method from p-methoxytoluene and fractionated on three-chain length compounds. Moreover, these fractions can be deposited by vacuum sublimation on indium tin oxide (ITO) substrates. Various characterisation methods are allowed which facilitated the understanding of the structural, electronic and optical properties of the PMPPs and a tentative of their correlation to chain length was presented.

The detection of metals by electrolyte–insulator–semiconductor (EIS)-type sensors involving p-tert-butyl calixarene layers and the trapping of dyes by modified cotton films have been studied by Rutherford Backscattering Spectrometry (RBS). According to the cage size, the absorption of Ag and Fe species was analyzed by RBS for calix[10] and calix[12]arene layers. The use of a simulation code allowed an evaluation of Na+ concentration detected by calix[4]arene membranes and revealed an inhomogeneous deposition of the evaporated layer, confirmed by AFM observations. First results on the adsorption of Cr and Mn containing dyes by cationized cotton films are reported. Opportunities and limits of the RBS analysis are discussed.

Thin p-tert-butyl calix[4]arene and p-tert-butyl calix[6]arene films were deposited using the technique of thermal evaporation under vacuum to fabricate chemical microsensors based on an E.I.S. (Electrolyte-Insulator-Semiconductor) structure. Electrochemical capacity measurements were made to test and calibrate physico-chemical sensors with regards to their sensitivity and selectivity. The sensing properties of calix[4]arene and calix[6]arene towards alkaline and heavy metal ions were tested. Both devices have shown Nernstian response and a wide working pH range. The former responded well to sodium ions and the latter to nickel ions, thus partial selectivity for these ions is shown. The improved lifetime (compared with membranes prepared by physical adsorption techniques) and sensitivity observed for these films indicates that these structures are worthy of further developments.

Thin calix[4]arene and calix[6]arene films were deposited using the technique of thermal evaporation under vacuum to fabricate chemical ion-selective field effect transistor (ISFET) microsensors. A high-performance liquid-phase chromatography (HPLC) method was used to verify the non-degradation of the calixarene layers, after the evaporation process. The sensing properties of these ionophores towards alkaline and heavy metal ions were tested. Both devices have shown Nernstian response and a wide working pH range. The former responded well to sodium ions and the latter to nickel ions, thus partial selectivity for these ions is shown. The improved lifetime membranes and sensitivity observed for these films indicates that these structures are worthy of further developments. (C) 1998 Elsevier Science S.A. All rights reserved.

By a simple and relatively easy method, we have synthesized a copolymer including alternatively p-phenylene vinylene and ether groups. The physicochemical characterization of this polymer has shown a high thermal stability, an amorphous structure and a small molecular weight (Mn ≈ 1100). The preliminary electrooptical study of this material shows an intense luminescence and a rectifying character of the polymer—metal contact.

Molybdenum disulfide is a very interesting material with numerous applications. However, to our knowledge, very few experimental works involving electrical measurements have been performed with this material up to now. This paper is devoted to the characterization of conduction mechanisms in thin layers and pressed pellets. The electronic structure related to the lubricating properties and the activation energy are determined using theoretical calculations (density functional theory) and experimental methods. A good agreement is found between the theoretical predictions and the experimental results. D.c. and a.c. conductivities are measured in the frequency range 10–107 Hz. The electronic transport mechanism is discussed in terms of Mott hopping in samples. The a.c. conductivity at high frequencies can be expressed by the formula σac(ω) = Aω11, where the slope n is close to 0.8.

In this paper we report some results about recognition reagents in an EIS (electrolyte—insulator—semiconductor) and ISFET (ion-sensitive field-effect transistor) type sensors, elaborated with a p-tert-butyl-calix [8] arene molecule. This calixarene was deposited by sublimation onto the surface insulator of the samples. Reflexion—adsorption infrared spectroscopy and X-ray diffraction were performed to characterize the chemical properties and the morphology of the layers. Electrochemical measurements were made to study the sensitivity and the selectivity of this sensitive membrane towards earth alkaline cations and the transition metals. A linear sensitivity was obtained only for the Ca2+. These devices exhibit a high chemical stability in liquid media and consequently can be used as sensors.

New high size calixarenes has been synthesized and tested as ionophores. We have studied the applications of these new even-membered macrocycles in the field of chemical sensors. Thin p-tert-butylcalix[l0 and 12]arenes film were deposited using the technique of thermal evaporation under vacuum on ISFET (Ion Sensitive Field Effect Transistor) and EIS structures (Electrolyte Insulator Semiconductor) surfaces. According to the HPLC chromatography, it was verified that the calixarene layers, after the sublimation process, undergo a degradation of the macrocycle. Electrochemical measurements with EIS structures and ISFETs were made to test the sensing properties of these calixarene films towards heavy metals. These high size calixarenes have shown a Nernstian sensitivity and a good selectivity towards iron (III) ions for the p-tert-butylcalix[12]arene and silver (I) ions for the p-tert-butylcalix[l0]arene A long lifetime, when tested in a large pH range, was obtained for these sensors. These materials present a real and great interest for further developments.

The research made to use organic materials as active elements in the electronic components and sensors has attracted much attention during the last decade, One of the interesting properties of these materials is the possibility to easily prepare stable and homogeneous thin films. In this work, we are interested in the study of the electrical properties of calixarene thin films using a metal-oligomer-semiconductor structure. The electrical study of such a structure can contribute to provide complementary information about the nature of the electrical conduction of the material and to elucidate the interface properties. The aim of this work is to study the different functioning parameters of ion selective field effect transistors and thin film transistors based on calixarenes.We present here the study of I-V characteristics and the behaviour of capacitance and conductance characteristics versus frequency, The annealing effects on the films are also investigated. (C) 1997 Elsevier Science S.A.

The proposed work deals with rapid thermal processing of ionic boron (11B+) and boron difluoride (BF2+), implanted in phosphorusdoped Cz-(100) silicon substrates through protecting oxide films, under different technological parameters. After implantation, the samples were rapidly thermally annealed at temperatures ranging from 900 to 1100 °C, in argon ambient gas, for different annealing durations. The rapid thermal annealings (RTAs) are carried out also, for some samples, after oxide mask removal. The total boron, fluorine as well as oxygen concentrations versus depth profiles, before and after annealing steps, in the SiO2/Cz-(100) silicon systems were determined using secondary ion mass spectrometry (SIMS). Using a background concentration, the junction depth in the substrate has been investigated under different annealing experimental conditions. The kinetic diffusion process of implanted boron into oxide and monocrystalline silicon during rapid thermal treatments has also been investigated. The reported results show that boron diffusion in the BF2+ case is widely reduced during rapid thermal treatments. Discussions of this are based on the effect of both knocked-on oxygen and fluorine on the boron diffusion kinetics.

New large size calixarenes have been synthesized and tested as ionophores. The applications of these new even-membered macrocycles in the field of chemical sensors have been studied. Thin p-tert-butyl calix[10 and 12]arenes film were deposited using the technique of thermal evaporation under vacuum on ISFET (Ion Sensitive Field Effect Transistor) and EIS structures (Electrolyte Insulator Semiconductor) surfaces. It was verified that by liquid chromatography the calixarene layers, after the sublimation process did not undergo any degradation. Electrochemical measurements with EIS structures and ISFETs were made to test the sensing properties of these calixarene films towards heavy metals. These large size calixarenes have shown a Nernstian sensitivity and a good selectivity towards iron(III) ions for the p-tert-butyl calix[12]arene and silver(I) ions for the p-tert-butyl calix[10]arene. A long lifetime was obtained for these sensors when tested over a large pH range. These materials present a real and great promise for further developments.

Fabrication and characterization of Schottky gated and metal semiconductor field-effect transistors based on molecular materials have been reported. In this paper, we present results on the transient properties of thin film transistors. The presence of a delay time when drain voltage is applied is studied. A discussion about the functioning principle of this class of devices is presented. Finally, the effect of both environment and different film treatments on the electrical characteristics is also investigated.

Many investigations on dielectric, electronic and spectroscopic characterisation have been achieved on molecular materials for their eventual application as sensors or electronic devices. Calixarenes exhibit an interesting supramolecular structure on account of their receptor properties; they represent receptor molecules of widely varying size for metal cations and organic molecules. They are comparatively new cyclic condensation products of para-substituted phenols and formaldehyde; they form a series of well-defined cyclic oligomers. Therefore, the variation of cavity size according to the requirements (i.e. ion sensitivities) of different guests is possible. The macro cycles are characterised by the phenolic unit number (4,6,8,…). p-tert-Butyl calix[n]arene (n = 4 and 8), used as a sensitive membrane incorporating the receptor molecule on the top of the gate oxide, was characterised. The calixarene was thermally evaporated on the oxide to form a semiconductor-oxide-film capacitance structure. It is shown, by means of structural and spectroscopic studies, that films have good adherence to the oxide and are chemically very stable allowing the use of such a structure as a chemical sensor in liquid media. The studies of ISFET structure using calix[n]arene membranes are in progress, showing an interesting selectivity and stability.