8 research outputs found
Electrical Characterisation of Ultra-thin SAM Structures
The way of reduction of metal oxyde semiconductor (MOS) structures is going
to reach limitations and new devices have to be explored as an alternative to
MOS technology. Molecular electronic and more particularly
self-assembly-molecular technique on silicon substrate gives interesting
results as seen in the literature. We are going to study n-alkyltrichlorosilane
grafting on oxidised silicon, characterise it macroscopically with ellipsometer
and goniometry measurements, and down to microscopic scale with atomic force
microscopy. Once the uniformity of the monolayer is verified (roughness of few
Angstr\"oms) we have tested a sputtering method deposition to form aluminium
dots onto the surface. Also metal-insulator-semiconductor diodes are tested
measuring both leakage current between gate and substrate and
capacitance-voltage. The sputtering method deposition can be improved in order
to decrease the gate leakage current and we would like to test another
evaporation method. Further application we want to study is gas sensors using
conjugated organic films or synthetic polymers and concerns the drift current
with gas absorption.Comment: Submitted on behalf of TIMA Editions
(http://irevues.inist.fr/tima-editions
Time-clustering behavior in the sequence of the aftershocks of the Al-Hoceima (Morocco) 24 February 2004 earthquake
The time dynamics of the aftershock sequence of the Al-Hoceima (Morocco) earthquake of 24 February 2004 has been investigated. The sequence of the occurrence times of the events with threshold magnitude <i>M<sub>th</sub></i>&ge;3.2 is characterized by a time-clustering behavior, identified using different fractal methods (Fano Factor, Allan Factor, Count-based Periodogram), well suited to reveal scaling features in point processes. The obtained results not only show the presence of memory phenomena and correlation structures in the Al-Hoceima aftershocks, but also furnish quantitatively the estimate of the magnitude of such correlation by means of the estimate of the scaling exponent &alpha;
Brillouin light scattering study of Langmuir-Blodgett films: elastic properties versus thickness
Brillouin light scattering was used to measure the elastic properties of a set of Langmuir–Blodgett films with varying thickness. Samples are constituted of stacks from 3 to 75 monolayers of a octabutoxyphthalocyanine copper derivative, deposited on Si substrates by the Langmuir–Blodgett (LB) technique. Due to the strong contrast in the elastic properties of the organic films and the substrate, it is shown that an elastic anomaly, if any, should be revealed by the Rayleigh mode and the first Sezawa mode which both strongly depend on the value of C44. Rayleigh and Sezawa dispersion curves are computed assuming that the elastic constants do not depend on the number of individual monolayers in the LB film. Within the accuracy of the experimental data, the theory well reproduces the trend of the effective velocities, showing so that the elastic properties of the material do not depend on the number of molecular monolayers in the stack
Hydrochemical constraints between the karst Tabular Middle Atlas Causses and the SaĂŻs basin (Morocco): implications of groundwater circulation
The karst Tabular Middle Atlas Causses reservoir is the main drinking-water supply of Fez-Meknes region (Saïs Basin) in Morocco. Recent analyses showed a decline in associated groundwater chemical quality and increased turbidity. To understand this hydrosystem, four surveys were undertaken during fall and spring, 2009–2011. Hydrogeochemical studies coupled with isotopic analyses (δ18O, δD and 222Rn) showed that the aquifers between the causses (mountains) and the Saïs Basin are of Liassic origin and at the southern extremities are of Triassic origin. Five recharge zones of different altitudes have been defined, including two main mixing zones in the south. Deuterium excess results suggest local recharge, while a plot of δ18O versus δD characterizes a confined aquifer in the eastern sector. 222Rn results reveal areas of rapid exchanges with an upwelling time of less than 2 weeks. A schematic conceptual model is presented to explain the groundwater circulation system and the behavior of this karst system