Experimental validation of the exponential localized states distribution in the variable range hopping mechanism in disordered silicon films

International audienceCarriers transport in low temperature (600°C) polycrystalline silicon thin film transistor channel region is studied for devices biased from weak to strong inversion. Analysis is supported by the theory of the 3D variable range hopping model due to hopping between localized electronic states near the Fermi level. The corresponding density of states is determined following an exponential (tail states) distribution associated to the statistical shift of the Fermi level

Fabrication of amorphous silicon nanoribbons by atomic force microscope tip induced local oxidation for thin film device applications

WOSInternational audienceWe demonstrate the feasibility of induced local oxidation of amorphous silicon by atomic force microscopy. The resulting local oxide is used as mask for the elaboration of thin film silicon resistor. A thin amorphous silicon layer deposited on a glass substrate is locally oxidized following narrow continuous lines. The corresponding oxide line is then used as mask during plasma etching of the amorphous layer leading to the formation of nanoribbon. Such amorphous silicon nanoribbon is used for the fabrication of resistor

THERMAL DEPENDENCE OF LOW-FREQUENCY NOISE IN POLYSILICON THIN FILM TRANSISTORS

International audienceThermal dependence of low frequency noise in low temperature (600°C) polysilicon thin film transistors is studied in devices biased from weak to moderate inversion and operating in the linear mode. Drain current noise spectral density, measured in the temperature range from 260K to 310K, is thermally activated following the Meyer Neldel rule. Analysis of the thermal activation of noise, supported by the theory of trapping/detrapping processes of carriers into oxide traps located close to the interface, leads to the calculation of the deep state interface distribution in function of the Meyer Neldel characteristic energy

Kinematics, topography, shortening, and extrusion in the India-Eurasia collision

Laurent Jolivet est Professeur à l'Université d'Orléans depuis le 1er Septembre 2009International audienceWe examine the problem of partitioning between shortening and extrusion in the India-Asia collision since 45 Ma. We compute the amount of shortening expected from the kinematics of India's motion with respect to Eurasia, using the reconstruction at collision time to put bounds on the possible amounts of surface loss within Greater India and within Eurasia. We then compute the amounts of surface loss corresponding to the thickened crust of Tibet and of the Himalayas, assuming conservation of continental crust. The spatial distribution of the topography reveals a large systematic deficit of crustal thickening distributed rather uniformly west of the eastern syntaxis but an excess of shortening east of it. This distribution indicates an important eastward crustal mass transfer. However, the excess mass east of the eastern syntaxis does not account for more than one third to one half of the deficit west of the eastern syntaxis. The deficit may be accounted either by loss of lower crust into the mantle, for example through massive eclogitization, or by lateral extrusion of nonthickened crust. A mass budget of the crust of the Himalayas indicates that lower crust has not been conserved there, but the deficit is so large that local loss in the mantle is unlikely to be the unique cause of the deficit. Alternatively, following Zhao and Morgan [1985], lower crust may have been transferred below the Tibetan crust. We conclude that a combination of possible transfer of lower crust to the mantle by eclogitization and lateral extrusion has to account for a minimum of one third and a maximum of one half of the total amount of shortening between India and Asia since 45 Ma. This conclusion leaves open the possibility that the partitioning between extrusion and loss of lower crust into the mantle on the one hand and shortening on the other hand has significantly changed during the 45 m.y. history of the collision

Thermal regime of the NW shelf of the Gulf of Mexico. 1) Thermal and pressure fields

National audienceThe thermal field of the Gulf of Mexico (GoM) is analyzed from a comprehensive temperature-depth database of about 8500 Bottom Hole Temperatures and Reservoir Temperatures. Our stochastic analysis reveals a widespread, systematic sharp thermal gradient increase between 2500 and 4000 m. The analysis of the pressure regime indicates a systematic correlation between the pressure and temperature fields

Numerical Simulation of Low-Frequency Noise in Polysilicon Thin-Film Transistors

3 pagesInternational audienceNumerical simulations of low-frequency noise are carried out in two technologies of N-channel polysilicon thin-film transistors (TFTs) biased from weak to strong inversion and operating in the linear mode. Noise is simulated by generation/recombination processes. The contribution of grain boundaries on the noise level is higher in the strong inversion region. The microscopic noise parameter that is deduced from numerical simulations is lower than the macroscopic one defined according to the Hooge empirical relationship and deduced from noise measurements. The higher macroscopic value is attributed to the drain-current crowding induced by nonconducting spots in the devices due to structural defects. The ratio of these two noise parameters can be considered as an indicator to qualify TFT technology

Etude des caractéristiques et du champ rayonné par le coupleur inductif d'un système de recharge sans contact pour véhicule électrique

Un système de recharge sans contact pour le véhicule électrique (VE) est considéré. Un modèle 3D par éléments finis (FE) du coupleur inductif est développé dans le but de calculer les inductances (Propres et Mutuelles) et le champ magnétique rayonné à travers le système. En outre, un modèle de circuit associé à un champ de calcul permet la détermination du comportement électrique du système pendant la charge. Les résultats de simulation sont ensuite validés par comparaison avec des mesures expérimentales. Le modèle développé permet la conception du système compte tenu de l'optimisation du transfert d'énergie et des contraintes de compatibilité électromagnétique rayonnée (CEM)

Homogénéisation de matériaux composites pour le blindage électromagnétique

Afin d'alléger la masse des systèmes dans le domaine des systèmes embarqués, le recours à des boîtiers de blindage en matériau composite commence à être envisagé. Malheureusement, les outils numériques classiques tels que Eléments Finis pour modéliser ces systèmes ne peuvent être utilisés car cela mène à un problème numérique trop complexe à résoudre à cause du trop grand écart entre l'échelle des hétérogénéités et celle de la structure. L'utilisation des méthodes d'homogénéisation est alors une solution pertinente pour étudier les matériaux composites. Ce papier présente un modèle d'homogénéisation dynamique valide sur une large gamme de fréquences

Numerical simulation of conduction and low-frequency noise in polysilicon thin film transistors

4 pagesInternational audienceNumerical simulations of static conduction and low-frequency noise are carried out in N-channel polysilicon thin film transistors. The Meyer-Neldel effect associated with the drain current is related to trapping/detrapping processes of carriers from dangling bonds located at the interface. Low-frequency noise is simulated by generation-recombination processes. The sources responsible of noise in the thin film transistors are mainly located close to the interface. The microscopic parameter deduced from numerical simulation is lower than the macroscopic one deduced from noise measurements. The ratio of these two parameters is considered as a factor of merit to qualify thin film transistor technology

Polycrystalline silicon nanowires synthesis compatible with CMOS technology for integrated gas sensing applications

International audiencePolysilicon nanowires are synthesized following a classical top-down approach using conventional UV lithography technique fully compatible with the existing silicon CMOS technology. N- and P-type in-situ doping of these nanowires is controlled over a large range of doping levels and electrical properties of these nanowires are analyzed. Results show that resistivity dependence with the doping level is both related to the nanowires size dependent structural quality and doping specie. Charged gas species (ammonia) sensitivity of these nanowires has also been studied. In addition, feasibility of N- and P-channel polysilicon nanowires transistors is demonstrated