Detection mechanism in highly sensitive ZnO nanowires network gas sensors

Metal-oxide nanowires are showing a great interest in the domain of gas sensing due to their large response even at a low temperature, enabling low-power gas sensors. However their response is still not fully understood, and mainly restricted to the linear response regime, which limits the design of appropriate sensors for specific applications. Here we analyse the non-linear response of a sensor based on ZnO nanowires network, both as a function of the device geometry and as a response to oxygen exposure. Using an appropriate model, we disentangle the contribution of the nanowire resistance and of the junctions between nanowires in the network. The applied model shows a very good consistency with the experimental data, allowing us to demonstrate that the response to oxygen at room temperature is dominated by the barrier potential at low bias voltage, and that the nanowire resistance starts to play a role at higher bias voltage. This analysis allows us to find the appropriate device geometry and working point in order to optimize the sensitivity. Such analysis is important for providing design rules, not only for sensing devices, but also for applications in electronics and opto-electronics using nanostructures networks with different materials and geometries

TiO2- and ZnO-Based Materials for Photocatalysis: Material Properties, Device Architecture and Emerging Concepts

Numerous kinds of photocatalysts such as oxide-, nitride- or sulfide-based semiconductors, conducting polymers or graphene oxide–based materials have emerged since the discovery of water splitting on TiO2 electrodes in 1972. Yet, metal-oxides are still largely the main family of materials promoted into photocatalytic applications

PRAP-CVD: A Novel Technique to Deposit Intrinsically Conductive Polymers

Polymers provide extraordinary opportunities for functionalizing surfaces integrated into flexible devices contributing to a significant advancement in thin-film technologies. Both the advantageous characteristics of conventional polymers (e.g. low weight, flexibility) and the functional physical properties of conventional semiconductors (e.g. absorption and emission of light and a tuneable conductivity) can be found in polymers providing innovative materials. Among polymers with heterocyclic structures, called conjugated polymers, polythiophene remains one of the most intensely researched materials in the field of so called organic electronics owing to the relatively facile and well-established synthetic modifications of the corresponding monomers and its derivatives. In particular, poly(3,4-ethylenedioxythiophene) (PEDOT) is one of the most promising owing to its exceptional stability, transparency, and electrical conductivity. Nevertheless it is difficult to process PEDOT into thin-films by traditional solution-based methods. Plasma Radicals Assisted Polymerisation via Chemical Vapour Deposition (PRAP-CVD) is a novel technique able to overcome the challenges caused by the conventional techniques

TiO2_{2}, ZnO, and SnO2_{2}-based metal oxides for photocatalytic applications: principles and development

This review mainly relied on advanced $\mathrm{TiO}_2$, ZnO, and $\mathrm{SnO}_{2}$ nanostructures for photocatalysis; therefore, their physical and chemical properties are hereafter summarized. We will discuss the various approaches that have been already proposed such as the doping, the heterostructure fabrication, and the use of plasmonic materials. We wish to draw here a particular attention to the semiconductor/semiconductor heterostructures

TiO2_{2}, ZnO, and SnO2_{2}-based metal oxides for photocatalytic applications: principles and development

This review mainly relied on advanced $\mathrm{TiO}_2$, ZnO, and $\mathrm{SnO}_{2}$ nanostructures for photocatalysis; therefore, their physical and chemical properties are hereafter summarized. We will discuss the various approaches that have been already proposed such as the doping, the heterostructure fabrication, and the use of plasmonic materials. We wish to draw here a particular attention to the semiconductor/semiconductor heterostructures

Synthesis of vanadium oxide films with controlled morphologies: Impact on the metal–insulator transition behaviour

Precise control over the growth of VO2 films with different morphologies is achieved by varying the deposition parameters in the DLI-MOCVD process such as temperature, pressure, concentration of precursor and time of deposition. In this study, thin films of VO2 with wide range of morphologies having Metal to Insulator Transition (MIT) temperature of (τc) ∼ 52 °C were deposited. Adjusting the process parameters has allowed the growth of highly porous nanocrystalline films and dense microcrystalline films with controlled crystallite size up to several hundred nanometres. Vanadium (V) oxy tri-isopropoxide was used in this study as a single source precursor. Porous films lead to a diffuse change in resistivity across the transition temperature while the crystalline films have sharp and high resistivity drop (Δρ). This enabled a qualitative study of the MIT behaviour with respect to the microstructure of the films and correlates the effect of deposition conditions to the obtained morphologies. Fine control over the morphology without additional doping or post deposition process provides the ability to tailor VO2 thin films for their respective applications. Scanning electron microscopy, Raman spectroscopy and X-ray diffraction were used to characterize the microstructure of the films while electrical resistivity measurements were carried out to observe the MIT behaviour of the films

Simulation of surface engineering for ultra shallow junction formation of PMOS for the 90nm CMOS technology node and beyond

Abstract-Since the junctions in the most advanced CMOS devices are thinner and thinner, the influence of the surface of silicon is thus becoming significant on dopant diffusion. In this paper, based on experimental data, a methodology for calibration is proposed, taking this effect of surface into account. SIMS profiles are accurately fitted by simulation using a simple model of recombination of interstitials; the phenomenon of POED is well reproduced and validated by TCAD 1D simulations. Then, the impact of POED on the PMOS performances is quantified by anticipation with 2D TCAD simulations

Comprehensive analytical modelling of an absolute pH sensor

In this work, we present a comprehensive analytical model and results for an absolute pH sensor. Our work aims to address critical scientific issues such as: (1) the impact of the oxide degradation (sensing interface deterioration) on the sensor’s performance and (2) how to achieve a measurement of the absolute ion activity. The methods described here are based on analytical equations which we have derived and implemented in MATLAB code to execute the numerical experiments. The main results of our work show that the depletion width of the sensors is strongly influenced by the pH and the variations of the same depletion width as a function of the pH is significantly smaller for hafnium dioxide in comparison to silicon dioxide. We propose a method to determine the absolute pH using a dual capacitance system, which can be mapped to unequivocally determine the acidity. We compare the impact of degradation in two materials: SiO2 and HfO2, and we illustrate the acidity determination with the functioning of a dual device with SiO2

The open-air site of Tolbor 16 (Northern Mongolia): Preliminary results and perspectives.

Numerous questions remain regarding the timing and the context of Upper Paleolithic emergence in Northeast Asia. Available data allow the recognition of a form of Initial Upper Paleolithic (IUP) documented in the Altai circa 45e40 ka 14C BP, and in the Cis- and Transbaikal around �37 ka 14C BP. In Northern Mongolia, a series of assemblages show intriguing similarities with IUP laminar assemblages from South Siberia and suggest long distance contact/movements of population during the first half of MIS3. These contacts are potentially enabled by the main river that drains into Lake Baikal, the Selenga. By cutting through the Sayan and the Yablonovy mountain ranges, the Selenga drainage system provides a potential corridor connecting South Siberia with the plains of Mongolia. The Tolbor 16 site (Ikh Tulberiin Gol, Northern Mongolia) is located circa 13 km from the confluence with the Selenga. The first results presented here suggest that the lithic assemblage and the ornaments discovered at Tolbor 16 document the early appearance of Upper Paleolithic in the region. This newly discovered site offers the possibility to generate high-resolution contextual data on the first appearance of the blade assemblages in Mongolia and to test the ‘Selenga corridor hypothesis’

Étude, réalisation et intégration de jonctions P+/N ultra-fines pour les technologies CMOS inférieures à 0,18 micromètre

La réalisation de jonctions ultra-fines est nécessaire à la formation des extensions du drain et de la source des transistors CMOS fortement sub-microniques. La formation de jonctions de type p+/n inférieures à 40 nm en profondeur nécessite l'utilisation d'implantation d'ions B+ à très faible énergie. Après avoir démontré les limites d'un tel procédé et notamment la saturation de la profondeur de jonction après implantation, nous avons étudié les techniques alternatives de dopage et en particulier le dopage assisté par faisceau laser. En raison de la finalité industrielle de nos travaux, le procédé de dopage par plasma (plasma doping) nous est apparu comme la solution la plus intéressante pour repousser les problèmes inhérents à l'implantation ionique standard (amélioration du triptyque performances/intégration/fiabilité). Ainsi, nous nous sommes attachés à développer et à caractériser cette nouvelle technique. Parallèlement à ces travaux, les mécanismes de diffusion anormale du bore ont été étudiés. L'intérêt d'un recuit d'activation dit "spike" a ainsi été démontré pour améliorer le compromis entre la résistance de couche Rj et la profondeur de la jonction Xj. Enfin, nous avons mis en évidence un nouveau phénomène de diffusion accélérée du bore. Nous l'avons nommée POED pour Post-Oxidation Enhanced Diffusion, cette diffusion anormale est induite par les oxydes sacrificiels conventionnellement utilisés en microélectronique. Les optimisations de chacun de ces facteurs ont permis d'améliorer les caractéristiques de la jonction et notamment le compromis universel de l'implantation Rj/Xj. Des jonctions aussi fines que 20 nm avec une résistance de couche égale à 1000 ohms/.. ont été fabriquées. Fabriquées par plasma doping et intégrées pour la première fois à des transistors de dimension 0,1-æm, elles ont permis d'obtenir des transistors fonctionnels dont les caractéristiques de sortie sont conformes aux spécifications requises. Nous avons également proposé une figure de mérite originale qui permet de prévoir en première approximation l'intérêt technologique d'une jonction ultra-fine à partir de son couple Rj/Xj.TOULOUSE-INSA (315552106) / SudocSudocFranceF