Nanoporous Ge thin film production combining Ge sputtering and dopant implantation

International audienceIn this work a novel process allowing for the production of nanoporous Ge thin films is presented. This process uses the combination of two techniques: Ge sputtering on SiO 2 and dopant ion implantation. The process entails four successive steps: (i) Ge sputtering on SiO 2 , (ii) implantation preannealing, (iii) high-dose dopant implantation, and (iv) implantation postannealing. Scanning electron microscopy and transmission electron microscopy were used to characterize the morphology of the Ge film at different process steps under different postannealing conditions. For the same postannealing conditions, the Ge film topology was shown to be similar for different implantation doses and different dopants. However, the film topology can be controlled by adjusting the postannealing conditions

Nanoporous Ge thin film production combining Ge sputtering and dopant implantation

In this work a novel process allowing for the production of nanoporous Ge thin films is presented. This process uses the combination of two techniques: Ge sputtering on SiO2 and dopant ion implantation. The process entails four successive steps: (i) Ge sputtering on SiO2, (ii) implantation preannealing, (iii) high-dose dopant implantation, and (iv) implantation postannealing. Scanning electron microscopy and transmission electron microscopy were used to characterize the morphology of the Ge film at different process steps under different postannealing conditions. For the same postannealing conditions, the Ge film topology was shown to be similar for different implantation doses and different dopants. However, the film topology can be controlled by adjusting the postannealing conditions

Modélisation des structures Métal-Oxyde-Semiconducteur (MOS) : Applications aux dispositifs mémoires

Our study concerns the modeling of MOS devices affected by defects which deteriorate their electric properties and consequently those of the memory devices. A great importance is given to the knowledge of the phenomena induced by the miniaturization of the capacity and transistor MOS which compose the memories. Our models, based on various studies of these subjects, represent new analysis tools geared to basic models in order to describe the complex operations of the memory devices. After a review of the symbols and basic equations used for MOS capacitors and MOS transistors, we summarize the memory history up to the use of dots. The second part of our work describes various MOS capacitor modeling developed in presence of parasitic effects such as poly-depletion of the gate, non uniformity of the substrate doping, non uniformity of the oxide layer, and the oxide fixed charges. From these models, we come up with a method to determine the repartition of the charges generated within the oxide layer after electrical stress and an analysis of the charge origin. The third part is devoted to MOS transistor modeling based on a segmented approach. This was applied to the series resistance study and the doping (gate and substrate) modeling, then extended to the modeling of ultra-thin insulator transistors. First, we present the modifications of MOS transistor IDS(VGS, VDS) characteristics induced by these non uniformities. Then, we use our models for the silicon nanocristal memories. We propose a model of charge storage in the dots close to the drain which enabled us to develop a model simulating writing operation of these memories. The electric characterizations of these structures with discrete traps are also analyzed by using the same models.Nos travaux concernent la modélisation des structures MOS affectées par des défauts qui détériorent leurs propriétés électriques et par conséquent celles des dispositifs mémoires. Nous avons attaché une grande importance à la compréhension des phénomènes liés à la miniaturisation de la capacité et du transistor MOS qui sont les composants électroniques élémentaires des mémoires. Nos modèles basés sur de nombreuses études réalisées sur ces sujets, représentent de nouveaux outils d'analyses pour créer les modèles de base décrivant le fonctionnement plus complexe des dispositifs mémoires. Après un rappel des notations et des équations de base utilisées pour les capacités MOS et les transistors MOS, nous retraçons l'évolution des dispositifs mémoires jusqu'aux mémoires à nanocristaux. Dans une deuxième partie de notre travail, nous décrivons les différentes modélisations de la capacité MOS développées en fonction de l'effet parasite considéré : la poly-désertion de la grille, la non uniformité du dopage du substrat, de l‘épaisseur d'oxyde et des charges fixes présentes dans la couche d'isolant. Nous avons ainsi pu proposer une méthode de détermination de la répartition de la charge générée dans l'oxyde par des stress électriques ainsi qu'une analyse de l'origine de ces charges. La troisième partie est consacrée aux modélisations du transistor MOS basées sur une approche segmentée. Celle-ci a été appliquée à l'étude des résistances séries et aux modélisations des dopages (grille et substrat), puis étendue à la modélisation des transistors à isolants ultra-minces. Nous présentons notamment les modifications de la caractéristique IDS(VGS,VDS) du transistor MOS induites par les non uniformités énumérées ci-dessus. Enfin, nous appliquons nos modèles aux mémoires à nanocristaux de silicium. Nous proposons une modélisation de la charge localisée dans les nodules proches du drain, ce qui nous a permis de développer un modèle simulant l'opération d'écriture de ces mémoires. Les caractérisations électriques de ces structures à piégeages discrets sont également analysées à l'aide de nos modèles

Modélisation des structures métal-oxyde-semiconducteur (MOS) (applications aux dipositifs mémoires)

AIX-MARSEILLE1-Inst.Médit.tech (130552107) / SudocLIMOGES-ENSCI (870852305) / SudocSudocFranceF

Ozone Sensor on Flexible Substrate by ZnO nanoparticles

International audienceIn this work the ozone detection in flexible substrate has been investigated. The flexible test platform with an integrated heater was designed and then characterized by thermal simulations using finite elements and its electrical properties have been studied. ZnO nanoparticles were deposited by drop coating process on the flexible substrate with platinum interdigited electrodes for gas detection. The gas sensing properties were determined by ozone exposure at different concentrations and temperatures. The gas sensing measurements present good response at different gas concentrations, good repeatability and fast recovery

Nozzle-less Ultrasonic Spray Deposition for Flexible Ammonia and Ozone Gas Sensors

In the last years printing and flexible electronic is transforming the way we used electronic devices. Among these, special interest is given to the development of gas sensors for industrial and environmental applications. Nozzle-less ultrasonic spray deposition is a simple and precise technique, which offers good homogeneity and high quality of the sensitive thin film. In addition, it represents a potential fabrication process for flexible electronic with low cost production and low waste of material. In this paper, nanoparticles of zinc oxide were deposited by nozzle-less ultrasonic spray deposition on flexible substrate. The sensing properties towards reducing and oxidizing gases in function of the operational temperature are reported. The flexible platform consists in titanium/platinum interdigitated electrodes and a micro-heater device, both fabricated by lift-off and photolithography. The operating temperature of the sensor is also challenging in term of power consumption. It is allowing the reaction with the exposure gases. Most of the semiconducting metal oxide materials used for gas sensing applications require high temperatures above 250 °C. Flexible gas sensors fabricated in this work present good responses towards ammonia and ozone at 300 °C and 200 °C respectively, with fast response and recovery time in a wide range of gas concentration

Direct Laser Patterning of a Gas Sensor on Flexible Substrate

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Trends in metal oxide thin films: Synthesis and applications of tin oxide

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Ammonia sensing properties of ZnO nanoparticles on flexible substrate

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