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Dans cet article, on s'interesse aux differentes filieres d'elaboration du dispositif photovoltaique: tout d'abord , les avantages et les inconvenients de la premiere generation de cellules a base de silicium cristallin,principalement monocristallin et multicristallin; ensuite, les proprietes des cellules inorganiques en couches minces, a base de silicium ou d’autres elements ; et enfin les concepts avances pour atteindre des tres hauts rendements. Le dernier paragraphe est consacre a l’etat actuel du marche photovoltaique en termes de production de modules et de leurs couts et a la place de l’energie photovoltaique dans le portfolio de production mondiale de l’energie.

Recent developments in organic solar cells show interesting power conversion efficiencies. However, with the use of organic semiconductors and bulk heterojunction cells, many new concepts have to be introduced to understand their characteristics. Only few models investigate these new concepts, and most of them are one-dimensional only. In this work, we present a two-dimensional model based on solving the drift-diffusion equations. The model describes the generation of excitons in the donor phase of the active layer and their diffusion towards an interface between the two separate acceptor and donor domains. Then, when the exciton reaches the interface, it forms a charge transfer state which can split into free charges due to the internal potential. Finally, these free charges are transported toward the electrodes within their respective domains (electrons in acceptor domain, holes in donor domain) before being extracted. In this model, we can follow the distribution of each species and link it to the physical processes taken into account. Using the finite element method to solve the equations of the model, we simulate the effect of the bulk heterojunction morphology on photocurrent curves. We concentrate on the morphology parameters such as the mean acceptor/donor domain sizes and the roughness of,the interface between the donor and acceptor domains. Results are discussed in relation with experimental observations.

A variety of defect healing methods was analyzed for optimization of polycrystalline silicon (poly-Si) thin-film solar cells on glass. The films were fabricated by solid phase crystallization of amorphous silicon deposited either by plasma enhanced chemical vapor deposition (PECVD) or by electron-beam evaporation (EBE). Three different rapid thermal processing (RTP) set-ups were compared: A conventional rapid thermal annealing oven, a dual wavelength laser annealing system and a movable two sided halogen lamp oven. The two latter processes utilize focused energy input for reducing the thermal load introduced into the glass substrates and thus lead to less deformation and impurity diffusion. Analysis of the structural and electrical properties of the poly-Si thin films was performed by Suns-VOC measurements and Raman spectroscopy. 1 cm2 cells were prepared for a selection of samples and characterized by I–V-measurements. The poly-Si material quality could be extremely enhanced, resulting in increase of the open circuit voltages from about 100 mV (EBE) and 170 mV (PECVD) in the untreated case up to 480 mV after processing.

Silicon rich silicon oxynitride (SRSON) were deposited by ECR-PECVD to form silicon nanostructures. The effect of argon flow during the deposition was investigated. The silicon nanoparticles were fabricated by a classical thermal treatment of SRSON films. The structural properties of the SRSON films were investigated by RBS and FTIR measurements. We show that the silicon excess in the SiOxNy matrix changes slightly with Ar flow but it has a significant impact on the silicon nanoparticles morphology embedded in the silicon oxynitride layer. Different shapes for silicon nanostructures ranging from separated Si nanocrystals to Si nanocolumns were formed as studied by energy-filtred transmission electron microscopy analysis (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This work aims at designing a new poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)-free multilayered system for bulk heterojunction organic solar cells. We propose a multilayer structure of glass/indium tin oxide/tetrasulfonated copper phthalocyanine/poly(3-hexylthiophene):[6,6]-C61-butyric acid methyl ester/aluminum (ITO/TS-CuPc/P3HT:[60]PCBM/Al). In this architecture, the TS-CuPc is mainly used as a buffer layer instead of PEDOT:PSS and can also act as an electron-donor material and a hole-extraction layer. Photovoltaic devices with a short-circuit current density of 9.7 mA/cm2, a open-circuit voltage of 0.51 V, and a power conversion efficiency of 1.76% were achieved, without post deposition thermal treatment of the P3HT:[60]PCBM blend layer.

Thin film polycrystalline silicon films grown on glass substrate were irradiated with an infrared continuous wave laser for defects annealing and/or dopants activation. The samples were uniformly scanned using an attachment with the laser system. Substrate temperature, scan speed and laser power were varied to find suitable laser annealing conditions. The Raman spectroscopy and Suns-V oc analysis were carried out to qualify the films quality after laser annealing. A maximum enhancement of the open circuit voltage V oc of about 100 mV is obtained after laser annealing of as-grown polysilicon structures. A strong correlation was found between the full width half maximum of the Si crystalline peak and V oc. It is interpreted as due to defects annealing as well as to dopants activation in the absorbing silicon layer. The maximum V oc reached is 485 mV after laser treatment and plasma hydrogenation, thanks to defects passivation.

In this paper, we report on the photovoltaic properties of conventional organic photovoltaic solar cells integrating a sputtered ZnO interfacial film deposited on the absorber P3HT:PCBM layer. An emphasis has been put on the influence of the annealing temperature and time for restoring and controlling the P3HT:PCBM/ZnO interface morphology, which can be damaged by the sputtering process. We show a significant improvement in the current-voltage (J-V) characteristics upon annealing up to 160 degrees C. This is evidenced by the reduction of the S-shape of these curves systematically observed for the cells integrating thick (100 nm) sputtered ZnO films. This approach was also highlighted on cells containing thinner (20 nm) ZnO films using a longer annealing process at 140 degrees C, which led to a significant improvement of the power conversion efficiency compared with the value recorded in as-prepared cells or in cells with no interfacial ZnO layer. These photovoltaic performances have been related to the change of the morphology of the absorber layer and to the vertical phase segregation of P3HT:PCBM at the interface with ZnO. Optical microscopy, scanning electron microscopy and atomic force microscopy have been performed in order to confirm this approach.

In this letter, we propose to introduce the notion of equivalent capacitance and to generalize the so-called equivalent-thickness concept to model arbitrary shapes of lightly doped nonplanar multigate MOSFETs, without the need to introduce any unphysical parameter. These definitions, which merely map a multigate geometry into the symmetric double-gate (DG) MOS-FET topology, have been validated by extensive comparison with 3-D numerical simulations of quadruple-gate, triple-gate (TG), triangular gate, cylindrical gate-all-around, and DG Fin Field Effect Transistors (FinFETs). Based on this modeling approach, any multigate architecture inherits of the fundamental relationships that have been developed for planar DG MOSFETs, including the normalization of all electrical quantities that considerably simplifies its analysis. In addition, considering a constant mobility, we find that the model can predict electrical characteristics of FinFETs from 275 to 425 K, without the need for any additional parameters. Finally, we were able to predict electrical measurements of a TG MOSFET, making of this generic model an interesting candidate for a design-oriented compact model for arbitrary multigate MOSFETs geometries.

Heavily doped emitters with low saturation current density are of particular interest for selective emitter solar cells. These emitters can be obtained by laser doping through the phosphosilicate glass layer formed after thermal diffusion from POCl 3 gas. The experimental results show that in contrast to purely POCl 3 furnace-diffused emitters, the saturation current density of laser-doped emitters does not increase linearly as sheet resistance decreases, but rather features two distinct regimes. In one of these regimes, the saturation current density is found to decrease as the sheet resistance decreases, reaching values lower than those of furnace emitters. This peculiar behaviour was explained by both qualitative analysis and numerical simulations.

We report on the electronic properties of Fe and Cr in n-type germanium using conventional and Laplace DLTS techniques, which in the case of Schottky barriers, are restricted to levels located in the upper half of the band gap. In this work we present extensive DLTS and Laplace DLTS results, re-examining various basic properties of Fe and Cr in n-type Ge samples. In addition our analysis bring new insights into the microscopic behavior of these two chemical species such as their interactions with hydrogen present as an unwanted contaminant, giving rise to the generation of other related levels in the band gap.

This paper presents the fabrication of thin film crystalline silicon solar cells on foreign substrates like alumina, glass–ceramic (GC) and metallic foils (ferritic steel—FS) using seed layer approach, which employs aluminium induced crystallisation (AIC) of amorphous silicon. Effect of hydrogen content in a-Si:H precursor films on the AIC process has been studied and the results showed that defects in the AIC grown films increased with increase of hydrogen content. At the optimal thermal annealing conditions, the AIC grown poly-Si films showed an average grain size of 7.6, 26, and 8.1 μm for the films synthesised on alumina, GC, and FS, respectively. The grains were (1 0 0) oriented with a sharp Raman peak around 520 cm −1 . Similarly, n-type seed layers were also fabricated by over-doping of as-grown AIC layers using a highly phosphorus doped glass solution. The resistivity of as-grown films reduced from 8.4×10 −2 Ω cm (p-type) to 4.1×10 −4 Ω cm (n-type) after phosphorus diffusion. These seed layers of n-type/p-type were thickened to form an absorber layer by vapour phase epitaxy or solid phase epitaxy. The passivation step was applied before the heterojunction formation, while it was after in the case of homojunction. Open circuit voltage of the junctions showed a strong dependence on the hydrogenation temperature and microwave (μW) power of electron cyclotron resonance (ECR) plasma of hydrogen. Effective passivation was achieved at a μW power of 650 W and hydrogenation temperature of 400 °C. Higher values of solar conversion efficiencies of 5% and 2.9% were achieved for the n-type and p-type heterojunction cells, respectively fabricated on alumina substrates. The analysis of the results and limiting factors are discussed in detail.

The purpose of this work is to determine the optimal parameters required to crystallize thin amorphous silicon films on glass substrate with a continuous wave (CW) laser diode ( λ = 808 nm), using a numerical model developed in COMSOL Multiphysics. The numerical simulation of the laser crystallization process takes into account the solid–liquid phase change and the difference between the melting temperature of amorphous (Tm a-Si = 1420 K) and that of crystalline silicon (Tm c-Si = 1690 K). We have varied the main parameters controlling the crystallization process, namely the power and the scan speed of the laser beam. Furthermore the initial temperature as well as the thickness of the a-Si:H layer were also taken as a parameter to optimize the process. We have determined the melting, crystallization and ablation energy threshold versus the different operational parameters.

Heavily doped emitters with low saturation current density are of particular interest for selective emitter solar cells. These emitters can be obtained by laser doping through the PSG layer formed after thermal diffusion from POCl3 gas. The experimental results show that in contrast to purely POCl3 furnace-diffused emitters, the saturation current density of heavily laser-doped emitters decreases as sheet resistance decreases. This peculiar behavior was explained by both qualitative analysis and numerical simulations. Surface recombination velocities were also investigated and revealed that while lightly laser-doped emitters were sensitive to surface state, heavily laser-doped emitters saturation current densities were only weakly dependant on recombination at the surface. Laser-doped selective emitter solar cells were also processed and featured an absolute overall gain of 0.6% in efficiency.

Swift heavy ions have unique feature of creating ion tracks in insulators of dimension from a few nm to about 10 nm. This particular feature of the swift heavy ions is used to engineer the size and shape of the nanoparticles embedded in silica matrix. On the basis of several experiments, it is evidenced that the embedded nanoparticles either grow in size or reduce in size, if they are smaller than or comparable to the ion track size. The shape transformation from spherical to elongated along the beam direction occurs, when the nanoparticle size is larger than the ion track diameter in silica. The reduction, growth and elongation of Au nanoparticles embedded in silica matrix under swift heavy ion irradiation have been discussed in the frame work of thermal spike model.

We have studied the optical properties of ZnTe nanocrystals (ZnTe-nc) embedded in a SiO 2 matrix by spectroscopic ellipsometry. The ZnTe-nc are embedded in a SiO 2 matrix by ion implantation technique. The dose of 2.9 x 10 16 cm -2 of tellurium and zinc ions are implanted in a 250 nm thick SiO 2 layer thermally grown on Si with respective implantation energies of 180 and 115 keV. Subsequent thermal treatments at 700 °C lead to the formation of ZnTe-nc. Their size is characterized by transmission electron microscopy. Variable angle ellipsometric measurements are performed in air at room temperature at angles of incidence of 55, 60, and 65°. By taking into account defects caused by ion implantation in silica matrix the critical points (CPs) dispersion model is used in order to extract the optical responses of the ZnTe-nc. The determined dielectric function spectra reveals distinct structures attributed to direct band gap and optical transition at higher energy. The observed structures are analyzed by fitting second derivative spectrum of the imaginary part of dielectric function with analytic CP line shapes. Results show good agreement with CPs data.

In this work, we applied low-impact energy secondary ion mass spectrometry (known as Sc-Ultra SIMS) and high lateral resolution (NanoSIMS50) to characterize the P3HT/PCBM (poly(3-hexylthiophene)/phenyl C61-butyric acid methyl ester bulk heterojunction photovoltaic (PV) devices. Here we report results obtained on Al/P3HT:PCBM/PEDOT:PSS/ITO (poly(3-hexylthiophene:phenyl C61-butyric acid methyl ester/poly(ethylene-dioxythiophene):poly(styrene sulfonate)/indium tin oxide) using advanced SIMS measurements to monitor 3D molecular compositions and metal/organic interface. The measurements have been performed on as-deposited as well as-annealed samples of Al/polymer interface. Blend macrophase separation and polymer/fullerene distribution have been investigated. Copyright © 2010 John Wiley & Sons, Ltd.

Use of germanium as a storage medium combined with a high-k dielectric tunneling oxide is of interest for non-volatile memory applications. The device structure consists of a thin HfO2 tunneling oxide with a Ge layer either in the form of continuous layer or discrete nanocrystals and relatively thicker SiO2 layer functioning as a control oxide. In this work, we studied interface properties and formation kinetics in SiO2/Ge/HfO2(Ge) multilayer structure during deposition and annealing. This material structure was fabricated by magnetron sputtering and studied by depth profiling with XPS and by Raman spectroscopy. It was observed that Ge atoms penetrate into HfO2 layer during the deposition and segregate out with annealing. This is related to the low solubility of Ge in HfO2 which is observed in other oxides as well. Therefore, Ge out diffusion might be an advantage in forming well controlled floating gate on top of HfO2. In addition we observed the Ge oxidation at the interfaces, where HfSiOx formation is also detected. © 2009 Elsevier B.V. All rights reserved., TÜBİTAK; Chalmers University of Technology

Up to now, P diffusion in Ge is modeled with an effective diffusivity involving at most a quadratic dependence with the free electron concentration (n). However, recent theoretical studies suggest the existence of a triply negatively charged state for the free vacancy in germanium and experimental data indicate that the E center (PV pair) in Ge has a double acceptor state. These two facts would be consistent with a diffusivity model involving a cubic dependence with n. In this paper the validity of this approach is checked for both pure thermal diffusion (intrinsic and extrinsic) and implanted phosphorus, using either our own experiments or other data available from the literature. Although some discrepancies still exist in some cases for the redistribution of implanted P, it is shown that the introduction of this cubic dependence significantly improves the overall agreement as compared with the usual model.

In this work, undoped amorphous silicon layers were deposited on n-type AIC seed films and then annealed at different temperatures for epitaxial growth. The epitaxy was carried out using halogen lamps (rapid thermal process or RTP) or a tube conventional furnace (CTP). We investigated the morphology of the resulting 2 μm thick epi-layers by means of optical microscopy. An average grain size of about 40 μm is formed after 90 s annealing at 1000 °C in RTP. The stress and degree of crystallinity of the epi-layers were studied by micro-Raman Spectroscopy and UV-visible spectrometer as a function of annealing time. The presence of compressive stress is observed from the peak position which shifts from 520.0 cm ―1 to 521.0 cm ―1 and 522.3 cm ―1 after CTP annealing for 10 min and 90 min, respectively. It is shown that the full width at half maximum (FWHM) varies from 9.8 cm ―1 to 15.6 cm ―1 , and the magnitude of stress is changing from 325 MPa to 650 MPa. Finally, the highest crystallinity is achieved after annealing at 1000 °C for 90 min in a tube furnace exhibiting a crystalline fraction of 81.5%. X-ray diffraction technique was used to determine the preferential orientation of the poly-Si thin films formed by SPE technique on n + type AIC layer. The preferential orientation is (100) for all annealing times at 1000 °C.

An explicit charge-based compact model for lightly doped FinFETs is proposed. This design-oriented model is valid and continuous in all operating regimes (subthreshold, linear, and saturation) for channel lengths (L) down to 25 nm, Fin widths (W-Si) down to 3 mn, and Fin heights (H-Si) down to 50 nm with a single set of parameters. It takes short-channel effects, subthreshold slope degradation, drain-induced barrier lowering, drain saturation voltage with velocity saturation, channel length modulation, and quantum mechanical effects into account.

Current researches on CMOS integrated Hall devices focus on the vertical Hall device (VHD) since this structure limits the performances of monolithic three-dimensional Hall probes. The well known conventional horizontal Hall device (HHD) has probably been brought closed to its optimal performances while integrated in CMOS technologies. On the contrary, the VHD which is more complex to study theoretically still asks for a better understanding in order to improve its performances that are lower than those of a HHD as it was demonstrated experimentally in many previous works. The aim of this paper is to discuss this experimentally observed difference between VHD and HHD through an analysis of 2D FEM calculations. Especially, we explain why the conventional VHD with two sensing contacts exhibits an intrinsic lower sensitivity. This lower sensitivity is responsible for the lower signal to noise ratio and the higher offset. We also introduce coefficients which allow to determine the sensitivity of a VHD depending on its geometry. Finally we explain why a measurement of the Hall voltage through four sensing contacts instead of two is mandatory to reach the maximum sensitivity.

This paper deals with an image segmentation process using a new fuzzy Markov model, which characterizes the imprecision of the hidden data and the correlation of the observed data. We propose to extend a recent pairwise Markov chain model (PMC [W. Pieczynski, Pairwise Markov chains, IEEE Trans. Pattern Anal. Mach. Intell. 25 (5) (2003) 634-639]) to a fuzzy context, allowing us to treat a spatial correlated noise between neighboring observations. The new algorithm, called fuzzy pairwise Markov chain (FPMC), requires a more specific methodology in order to compute the posterior density related to the hidden field. We validate our approach through experiments performed on synthetic and real images.

Novel fullerene-grafted poly(3-hexylthiophene) (P3HT)-based rod-coil block copolymers have been synthesized. The regioregular P3HT rod block has been synthesized by a modified Grignard metathesis reaction (GRIM). An original in situ end-capping reaction has been developed in order to convert the P3HT block into an efficient macro-initiator for the nitroxide-mediated radical polymerization (NMRP) of the coil block. Controlled radical polymerization of the second poly(butylacrylate-stat-chloromethylstyrene) [P(BA-stat-CMS)] block has been done through various conditions leading to different coil block lengths. The final electron donor-acceptor block copolymer has been obtained after C 60 grafting in soft conditions. Copolymers have been characterized by 1 H NMR and size exclusion chromatography. Optical characterizations, before and after C 60 grafting, are reported.

This paper presents a new driving method allowing fast analogue light modulation with bistable ferroelectric liquid crystals (FLC). The method is evaluated using a functional virtual prototyping design flow. First, a surface stabilized binary FLC cell is modeled in VHDL-AMS language on the basis of well-known theories of FLC. Some physical and environmental phenomena are added (e.g. electronic behavior of the cell, temperature, etc.) in order to improve its reliability. Once the model is validated, a virtual prototype of a FLC pixel is performed by associating the model of the FLC cell and the model of an appropriate wave generator. Simulations show that our new driving method works, but with certain limitations. The most critical one seems to be the high temperature dependence of the pixel response.

This paper describes an integrated analogue instrumental chain dedicated to measuring magnetic pulses with an amplitude of a few tens or hundreds of microteslas, superimposed to a strong static magnetic field, i.e. 1.5 T. The system features a silicon Hall sensor with nested-chopping-like biasing circuitry, DC Hall voltage compensation, amplifying and multistage filtering. Low-noise performances are achieved by applying 100 kHz spinning current to the Hall device and chopping at 200 kHz to the signal conditioning blocs downstream. The microsystem achieves 20 μT resolution over a 1.6 kHz bandwidth extending from 5 Hz to 1.6 kHz under 1.5 T static field.

A physics-based compact model including short-channel effects (SCEs) is presented for undoped (or lightly doped) symmetric double-gate (DG) MOSFETs. Our approach allows an accurate description of the device behavior down to 60 nm with a simple set of equations. It is shown that the subthreshold current, the threshold voltage roll-off and the DIBL predicted by the analytical solution are in close agreement with 2-D numerical simulations performed with Atlas. The mobility degradation due to both transverse and longitudinal fields is taken into account but the channel length modulation (saturation regime) is not addressed in this paper. In order to demonstrate that the model is well-suited for circuit simulation, the results of the dynamic model based on an explicit formulation of the mobile charge density are also presented. (C) 2007 Elsevier Ltd. All rights reserved.

The progress achieved in the various epitaxial-growth procedures is significant enough today to allow the addressing of new questions related to the structures at the atomic scale of various defects in alloy materials. In this review we shall focus particularly on SiGe which is miscible in all proportions. The chemical disorder, resulting from mixing-entropy constraints, offers a large distribution of atomic environments around a given point defect. In the immediate neighborhood of the defect, which we shall restrict mainly to the first two or three atomic shells, none of the existing imaging techniques can provide any reliable information. On the other hand, electronic transport techniques, based on carrier capture and emission processes turns out to be very sensitive to the local atomic environment. The highly localized character of the wavefunction of the carriers trapped at the defect links the atomic environment of the defect to the carrier properties. In this work we shall illustrate these features for some simple but technologically important point defects in relaxed SiGe and makes an inspired guess at their atomic structures.

We present a study on amorphous SiO/SiO 2 superlattice performed by grazing-incidence small-angle X-ray scattering (GISAXS). Amorphous SiO/SiO 2 superlattices were prepared by high-vacuum evaporation of 3 nm thin films of SiO and SiO 2 (10 layers each) onto Si(1 0 0) substrate. After the deposition, samples were annealed at 1100 °C for 1 h in vacuum, yielding to Si nanocrystals formation. Using a Guinier approximation, the shape and the size of the crystals were obtained. The size of the growing nanoparticles in the direction perpendicular to the film surface is well controlled by the bilayer thickness. However, their size varies more significantly in the direction parallel to the film surface.

Polycrystalline lead iodide layers with crystallites in the micrometer range have been prepared using a solution growth method from water and polyvinyl alcohol. Structural, electrical and optical measurements have been performed to characterize these layers and compare their properties to those of polycrystalline films prepared by solution growth in pure water. Most of these properties are very similar. The main difference comes from the photoresponse: that of films prepared with PVA remains high but presents an unusual behaviour with temperature. This has been related to the presence of a trapping/recombination energy level in the band gap. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

It is well known that the CdTe material suffers from the presence of native defects, due to the introduction of dislocations by pressure owing to its mechanical brittleness. Within this framework, we present a study of the dislocations effect on the electric properties of the CdTe material, using measurements by C(V) and I(V) and IR absorption. The adopted method for the plastic deformation is the Vickers microhardness at room temperature and under various weights (10, 25, 50 and 80 g). The following results have been obtained: a reduction in the donors concentration, an increase in the leakage current as well as a reduction of the band gap and finally a drastic variation of the Schottky barrier where we could observe two distinct behaviours depending on the used side (Cd or Te) for the contact deposition.

International audience; Cet article présente une stratégie complète d'identification et de commande d'un filtre actif parallèle améliorant les performances des systèmes classiques de dépollution des installations électriques. Basée sur des techniques neuromimétiques, notre approche s'adapte aux variations de charge du réseau et donc aux fluctuations des perturbations harmoniques. De plus, les réseaux neuromimétiques rendent la structure de calcul homogène pour une implémentation matérielle en temps-réel. Des simulations démontrent les caractéristiques originales de cette stratégie et des résultats expérimentaux permettent de valider la robustesse de l'approche.

High-speed cameras use the interesting performances of CMOS imagers that offer advantages in on-chip functionalities, system power reduction, cost, and miniaturization. The FAst MOS Imager (FAMOSI) project consists in reproducing the streak camera functionality with a CMOS imager. In this paper, a new imager called FAMOSI 2, which implements an electronic shutter and analog accumulation capabilities inside the pixel, is presented. With this kind of pixel and the new architecture for controlling the integration, FAMOSI 2 can work in repetitive mode for low light power and in single shot mode for higher light power. This repetitive mode utilizes an analog accumulation to improve the sensitivity of the system with a standard n-well/$ p_ sub$photodiode. The characterization has been realized in single shot mode to optimize the accumulation mode. The prototype has been fabricated in the Austriamicrosystems 0.35-$muhboxm$CMOS process. The chip is composed of 64 columns$times$64 rows of pixels. The pixels have a size of 20$muhboxm$$times$20$muhboxm$and a fill factor of 47%.

Spectroscopic ellipsometry is used to investigate optical properties of cobalt-implanted silica thin films. The films under investigation are 250 nm thick thermal SiO 2 layers on Si substrates implanted with Co + ions at energy of 160 keV and at fluences of 10 17 ions/cm 2 for different temperatures of substrate during implantation (77 and 295 K). Changes due to Co + implantation are clearly observed in the optical response of the films. Optical behaviours are furthermore different for the three implantation temperatures. To understand the optical responses of these layers, the ellipsometric experimental data are compared to different models including interference effects and metal inclusions effects into the dielectric layer. The simulated ellipsometric data are obtained by calculating the interferences of an inhomogeneous layer on a Si substrate. The material within this layer is considered as an effective medium which dielectric function is calculated using the Maxwell-Garnett effective medium approximation. We show that although the structures of these layers are very complicated because of ion-implantation mechanisms, quite simple models can provide relatively good agreement. The possibilities of ellipsometry for the study of the optical properties of such clusters-embedded films are discussed. We especially provide the evidence that ellipsometry can give interesting information about the optical properties of nanostructured layers. This is of special interest in the field of nanostructured layered systems where ellipsometry appears to be a suitable optical characterization technique.

A three-dimensional model is proposed to describe single electron charging into the nanocrystals that compose the floating gate of a metal-oxide-semiconductor transistor. It is built on the physical and geometrical parameters of the device. If the nanocrystals have a cylindrical symmetry, the 3D approach can be analytically reduced to a 2D model. Different effects that play an important part on single electron charging, such as the electrostatic coupling between two nanocrystals and the doping density of the channel, are analysed. Moreover the necessity of including the excited states of the nanocrystals and the subbands of the channel is shown. Finally the tunneling times to charge the nanocrystals in the floating gate from the channel are simulated and discussed.

International audience; A series of polystyrene (PS) and fullerene (C-60) based thin films containing from 23 to 60 wt.% in fullerene were investigated. Initially, the films were characterised by Fourier Transform Infrared Spectroscopy (FTIR) spectroscopy where the characteristic absorption bands of both the fullerene and the polystyrene were revealed. The additional characteristic absorption bands due the grafted fullerene to polystyrene were revealed as well. The relative peak intensities provided with qualitative information of the films stoichiometry in terms of the fullerene's amount that was grafted to polystyrene. The optical properties of the films were investigated by spectroscopic ellipsometry (SE). It was found that the increase of the fullerene's amount that was grafted to polystyrene results in an increase of the absorption coefficient a, refractive index n, extinction coefficient k as well as in the dielectric constant epsilon(proportional to) within the range between 2.4 and 2.8 for the lower and higher fullerene content, respectively. The films' J-V characteristics, of the space charge limited current (SCLC)) behaviour, showed increased currents with increasing the fullerene's content. The electron mobility was extracted and found to increase with increasing the fullerene amount, from 4 x 10(-9) cm(2) V/s to 2 x 10(-7) cm(2) V/s.

In this work was investigated numerically and experimentally a simple laser doping method employing borosilicate (BSG) glass films as dopant sources which are deposited onto Si by the spin-coating technique. Both short (20 ns) and long (200 ns) pulse duration Excimer laser beams were used to deposit a large amount of energy in short time onto the near-surface region. Under suitable conditions, the irradiation leads to surface melting and dopant incorporation by liquid phase diffusion from the surface. Boron distribution profiles in the two-pulse duration regimes were studied as well as their electrical properties, and the junction formation of less than 25 nm in depth was demonstrated.

In quantum flash memories, the floating gate is a nanocrystal (NC) layer which can be charged from the channel. To our knowledge, no attempt has been carried out to evaluate the interactions between nanocrystals inside a layer. On the contrary, since the NCs are commonly supposed to be independent, reduced systems of single NC are often considered. In our model and simulations, we show that the NC charging is not only related to relevant thicknesses (tunnel, oxide) and NC radii, but also to the electrostatic coupling that exists between two nanocrystals inside the floating gate layer.

Ionic irradiation is used to magnetically pattern CoPt alloy films, using an appropriate mask to protect arrays of CoPt dots with a 1 μm 2 size, while the remainder of the film is exposed to ionic irradiation. Before irradiation, we obtain a layer with the Ll 0 tetragonal structure, ordered and with a strong perpendicular magnetic anisotropy energy in the growth direction. After irradiation, the unprotected regions become disordered and magnetically soft, whereas the protected regions remain magnetically hard. Spatially selective irradiation thus provides a spatial distribution of magnetic anisotropy and hence of the magnetization direction, perpendicular to plane in the ordered zones and in-plane in the disordered zones. The interest of ionic irradiation is that the film recovers its initial roughness after elimination of the mask which is promising for the data storage applications.

In this work, the influence of light absorption on copper related defect reactions in p-type silicon is investigated by transient ion drift measurements. It is found that copper out-diffusion and formation of copper complexes are two competitive processes whose relative importance depends on light intensity. At low intensities, a reduced surface potential allows complete copper out-diffusion. Above a certain threshold value, however, copper complexes are formed which could be responsible for the earlier reported optically activated recombination activity of copper in silicon. It is shown that the observed Fermi-level dependence of the defect formation rate cannot be explained in terms of an optically induced change in the interstitial copper charge state. The high thermal stability of the formed copper complexes further points out that the formation of electrostatically bound copper-defect pairs may be ruled out.

X-ray powder and high-resolution single-crystal diffraction techniques were used to study the irradiation damage of fluorapatites. Krypton, iodine and carbon irradiations were performed at high energy (≈1 MeV/a) in the 1011 to 5 × 1013 cm−2 fluence range. Both diffraction techniques showed a strong unit-cell increase of the fluorapatite structure, with a full relaxation of the remaining part of the material for large fluences. X-ray powder experiments revealed an amorphization of the material up to 85% for fluences around 1013 ions cm−2. Simulation of the relationship between amorphous volume fraction and fluence evidenced that the amorphization mechanisms could be dominated by a single impact process for iodine and double impacts for krypton. The effective radius of the track core remained nearly constant although the electronic energy loss increases from Kr to I. Moreover total amorphization of fluorapatite irradiated by swift heavy ions could not be obtained in this study. Experiments performed on (0 0 2)-oriented single-crystals allowed us to separate the change of the c-parameters of the damaged and virgin phases, and pointed out an anisotropic response of the material to the damage process.

We used a combination of ion irradiation and e-beam lithography to magnetically pattern an ordered CoPt alloy with strong perpendicular magnetic anisotropy. Ion irradiation disorders the alloy and strongly reduces the magnetic anisotropy. Magnetic force microscopy showed a regular array of 1μm2 square dots with perpendicular anisotropy separated by 1 μm large ranges with in-plane anisotropy. This is further confirmed by magnetic measurements, which showed that arrays protected by a 200 nm Pt layer present the same coercive field and the same perpendicular anisotropy as before irradiation. This is promising for applications in magnetic recording technologies.

A naphthalenediimide derivative 3a carrying TEMPO radical and azobenzene substituent was found to show photoresponsive magnetic as well as FET properties upon illumination. The alteration of its mo...

National audience; La filière master à spécialité micro-nano électronique de l'université de Strasbourg propose un enseignement pratique de la testabilité de circuits intégrés mixtes analogique-numérique. Une séquence pédagogique est présentée et guide l'étudiant dans le test d'un circuit capteur intégrant une chaine instrumentale complète. Cette séquence d'apprentissage utilise le testeur industriel du pôle de Montpellier avec lequel une connexion à distance permet d'assurer le pilotage de la carte de test. Deux volets sont abordés. Le premier volet traite du test numérique et concentre son action sur une fonction particulière du capteur qui implémente à la fois de la logique combinatoire et séquentielle. Les techniques de test standardisées de l'industrie y sont présentées et expérimentées. Le second volet oriente l'étudiant dans le test des fonctions analogiques du capteur où des approches de caractérisation permettent d'en évaluer les performances. Enfin, un regard est porté sur la méthodologie globale de conception d'un circuit intégré et de son test en particulier.

This paper investigates the surface passivation effect by silicon dioxide layer formed either by a thermal oxidation process at 800 °C or by plasma enhanced chemical vapor deposition (PECVD) method at 400 °C. The passivation was applied on n+ emitter of the p type multicrystalline silicon (mc-Si) of 1 Ω cm resistivity. The mc-Si wafers were taken from the same column of the Si cast ingot. The optical properties of thermal SiO2 and PECVD deposited SiO2 films have been investigated by ellipsometry measurements to deduce the refractive index and thickness. The reflectance spectra were measured by UV–vis–NIR spectrophotometry. For performing the antireflection (ARC) requirements in the finished solar cells, both silicon dioxide films have been covered by a TiO2 layer deposited by CVD. The mc-Si solar cells were prepared according to the technology elaborated in Photovoltaic Laboratory of IMMS. Spectral response (SR) and current–voltage (I–V) characteristics were measured and the data are correlated with optical results. The passivation effect induced by the thermal and PECVD Si dioxide layers on the solar cell parameters is discussed through the open circuit voltage and short circuit current data.

For the last few years, improvised peroxide based explosives are frequently used in acts of terrorism. Their simple design does not make them less threatening than those based on TNT because they are equally as powerful as those based on TNT (trinitrotoluene). In view of the major issues of the overall safety and, in particular, the citizens' protection, it becomes necessary to enjoy reliable detection instruments. Such is the background of this PhD work which aims to develop a built-in sensor,sensitive and selective to traces of explosives, especially those based on peroxide. This electronic nose is made up of a network of carbon nanotube field-effect transistors (CNTFET), and data processing hardware. After a brief introduction relating to CNTFETs for gaseous detection, we will provide the basis for the elaboration of an electronic modeling of the sensor. This modeling aims, at the end, to allow designers of integrated circuits to benefit from a simulation support of CNTFETs, required to the implementation of control and signal conditioning electronics. We will also detail what are the fundamental steps mandatory before the development of a predictive compact model based on physics, which means the topological understanding of the nanotubes network. Then, we will describe different probabilities of contacts between nanotubes. Later, we will introduce the elaboration of the electronics allowing the control of the voltages applied to the CNTFETs and the electrical signals conditioning. The objective of this conditioning is to carry electrical responses from the sensor to data processing architectures used for the detection of the different target gasses. High Voltage CMOS integrated electronics are powered by low-voltage batteries. Charge pumps and voltage boosters which generate these high voltages, have been investigated, modeled and carried out. We also provide in this dissertation a new charge pump architecture which offers, in some ranges of application, an interesting alternative to the most efficient charge pumps used until now.; Depuis quelques années, les explosifs artisanaux à base de peroxyde sont fréquemment utilisés dans les actes de terrorisme. Leur simplicité de conception ne les rend pas moins inoffensifs car ils sont tout aussi puissants que ceux à base de TNT (trinitrotoluène). Au regard des enjeux majeurs de la sécurité globale et en particulier de la protection du citoyen, il devient nécessaire de bénéficier d'instruments de détection fiables. C'est dans ce cadre que s'inscrit ce travail de thèse qui vise à développer un capteur intégré, sensible et sélectif aux traces d'explosifs, notamment ceux à base de peroxyde. Ce nez électronique est constitué d'une matrice de transistors à nanotubes de carbone (CNTFET) et d'une électronique et traitement des données. Après une brève introduction relative aux CNTFET pour la détection gazeuse, nous présentons les bases de l'élaboration d'une modélisation électrique du capteur. Cette modélisation a pour but, à terme, de permettre aux concepteurs decircuits intégrés de bénéficier d'un support de simulation des CNTFET, nécessaire à la mise en oeuvre de l'électronique de contrôle et de conditionnement des signaux. Nous détaillerons également ce qui constitue selon nous l'étape fondamentale précédant l'élaboration d'un modèle compact prédictif basé sur la physique, c'est à dire la compréhension topologique du réseau de nanotubes. Nous détaillerons alors différentes probabilités de contacts entre nanotubes. Nous présentons ensuite,l'élaboration de l'électronique permettant le contrôle des potentiels appliqués aux CNTFET et le conditionnement des signaux électriques. Ce conditionnement a pour objectif d'acheminer les réponses électriques du capteur vers des architectures de traitement de données utilisées pour la détection des différents gaz cibles. L'électronique intégrée en technologie CMOS HV (haute tension) est alimentée par pile basse tension. Des pompes de charge, élévateurs de tension, générant ces hautes tensions ont été étudiées, modélisées et réalisées. Nous proposons également dans ce manuscrit une nouvelle architecture de pompe de charge qui constitue, dans certaines plages d'utilisation, une alternative intéressante aux pompes de charge les plus performantes utilisées jusqu'à présent.

International audience

International audience

International audience

International audience