Defects in pulsed laser and thermal processed ion implanted silicon

The evolution of the nature and concentration of the defects produced by 100 or 300 keV As ions at fluences 1 to 4×10^–12 cm^–2 inn-type, Fz Silicon doped with 10¹⁵ to 10¹⁶ cm^–3 has been studied as function of thermal treatments (in the range 500°–900 °C) and of the energy density (in the range 0.3–0.6 J cm^–2) of a light pulse from a ruby laser (15 ns, 0.69 m). Deep-level transient spectroscopy (DLTS) combined with capacitance — voltage (C-V) measurements were used to get the characteristics (energy level, crosssection for the capture of majority carriers) of the defects and theirs profiles. The difficulties encountered in the analysis of the results, due to the large compensation of free carriers in the implanted region and to the abrupt defect and free carrier profiles, are discussed in detail and the corrections to apply on the C-V characteristics and the DLTS spectra are described. The defects resulting from the two types of treatments are found to be essentially the same. Only, for laser energies higher than 0.5 J cm^–2, the laser treatment appears to introduced new defects (atE0.32 eV) which should result from a quenching process. The fact that a laser energy smaller than the threshold energy for melting and recrystallization is able to anneal, at least partially, the defects produced by the implantation, demonstrates that the annealing process induced by the laser pulse is not a purely thermal process but is enhanced by a mechanism involving ionization.     

Fractionation and proteomic analysis of the Walterinnesia aegyptia snake venom using OFFGEL and MALDI‐TOF‐MS techniques

Animal venoms are complex mixtures of more than 100 different compounds, including peptides, proteins, and nonprotein compounds such as lipids, carbohydrates, and metal ions. In addition, the existing compounds show a wide range of molecular weights and concentrations within these venoms, making separation and purification procedures quite tedious. Here, we analyzed for the first time by MS the advantages of using the OFFGEL technique in the separation of the venom components of the Egyptian Elapidae Walterinnesia aegyptia snake compared to two classical methods of separation, SEC and RP‐HPLC. We demonstrate that OFFGEL separates venom components over a larger scale of fractions, preserve respectable resolution with regard to the presence of a given compound in adjacent fractions and allows the identification of a greater number of ions by MS (102 over 134 total ions). We also conclude that applying several separating techniques (SEC and RP‐HPLC in addition to OFFGEL) provides complementary results in terms of ion detection (21 more for SEC and 22 more with RP‐HPLC). As a result, we provide a complete list of 134 ions present in the venom of W. aegyptia by using all these techniques combined.     

Ionization enhanced crystallization in amorphous germanium

The effect of high-energy electron irradiation upon the kinetics of crystallization of amorphous germanium layers has been studied, using conductivity measurements, during isochronal and isothermal warm-up. An increase in the growth rate of crystallization, induced at the surface or in the bulk, has been observed. It is suggested that this increase is the consequence of the recombination of electron-hole pairs created by the irradiation.     

Ueber die L?slichkeit einiger organischen S?uren in Aether und Alkohol

Ohne Zusammenfassung     

Versatile Functionalization of Nanoelectrodes by Oligonucleotides via Pyrrole Electrochemistry

Surface modification at the nanometer scale is a challenge for the future of molecular electronics. In particular, the precise anchoring and electrical addressing of biological scaffolds such as complex DNA nanonetworks is of importance for generating bio‐directed assemblies of nano‐objects for nanocircuit purposes. Herein, we consider the individual modification of nanoelectrodes with different oligonucleotide sequences by an electrochemically driven co‐polymerization process of pyrrole and modified oligonucleotide sequences bearing pyrrole monomers. We demonstrate that this one‐step technique presents the advantages of simplicity, localization of surface modification, mechanical, biological and chemical stability of the coatings, and high lateral resolution.     

Carbon nanotube chemistry and assembly for electronic devices

Carbon nanotubes (CNTs) have exceptional physical properties that make them one of the most promising building blocks for future nanotechnologies. They may in particular play an important role in the development of innovative electronic devices in the fields of flexible electronics, ultra-high sensitivity sensors, high frequency electronics, opto-electronics, energy sources and nano-electromechanical systems (NEMS). Proofs of concept of several high performance devices already exist, usually at the single device level, but there remain many serious scientific issues to be solved before the viability of such routes can be evaluated. In particular, the main concern regards the controlled synthesis and positioning of nanotubes. In our opinion, truly innovative use of these nano-objects will come from: (i) the combination of some of their complementary physical properties, such as combining their electrical and mechanical properties; (ii) the combination of their properties with additional benefits coming from other molecules grafted on the nanotubes (this route being particularly relevant for gas- and bio-sensors, opto-electronic devices and energy sources); and (iii) the use of chemically- or bio-directed self-assembly processes to allow the efficient combination of several devices into functional arrays or circuits. In this article, we review our recent results concerning nanotube chemistry and assembly and their use to develop electronic devices. In particular, we present carbon nanotube field effect transistors and their chemical optimization, high frequency nanotube transistors, nanotube-based opto-electronic devices with memory capabilities and nanotube-based nano-electromechanical systems (NEMS). The impact of chemical functionalization on the electronic properties of CNTs is analyzed on the basis of theoretical calculations. To cite this article: V. Derycke et al., C. R. Physique 10 (2009).     

Étude optique des processus d'écoulement de solutions viscoélastiques

Résumé On précise les caractères principaux des variations de la viscosité, de l'angle d'extinction et de la biréfringence des systèmes: laurate de potassium-chlorure de potassium/eau. On montre que dans l'ensemble, ces propriétés ne peuvent pas être interprétées à l'aide des modèles habituels de particules rigides indéformables ou de particules globulaires déformables. Par contre, au prix d'un petit nombre d'hypothèses simples, on peut rendre compte, au moins qualitativement des phénomènes observés par la considération du modèle d'une suspension de particules dissymétriques mais déformables à la manière d'un fluide anisotrope et non d'un solide élastique.

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Zusammenfassung Die wesentlichen Merkmale der Veränderungen der Viskosität, des Auslöschungswinkels und der Doppelbrechung von den Systemen: Kaliumlaurat-, Kaliumchlorid-Wasser können genau bestimmt werden. Diese Eigenschaften werden nicht mit Hilfe der gewöhnlichen Modelle von starren unverformbaren oder kugelförmigen Teilchen im Ganzen erklärt. Im Gegenteil, man kann mit einer kleinen Zahl von einfachen Voraussetzungen wenigstens in einer qualitativen Weise die beobachteten Phänomene durch die Betrachtung des Modells einer Suspension von dissymetrischen und sich wie eine anisotrope Flüssigkeit, nicht aber wie ein elastischer Festkörper fließenden verformbaren Teilchen erklären.