Metallic temperature sensors on flexible substrate: Direct laser patterning, Inkjet printing

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Thermo-mechanical characterization of passive stress sensors in Si interposer

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TEM and XRD characterizations of epitaxial silicon layer fabricated on double layer porous silicon

International audienceSingle crystal Silicon (Si) layers have been deposited by molecular beam epitaxy on double-layer porous silicon (PSi). We show that a top thin layer with a low porosity is used as a seed layer for epitaxial growth. While, the underlying higher porosity layer is used as an easily detectable etch stop layer. The morphology and structure of epitaxial Si layer grown on the double-layer PSi are investigated by high resolution X-ray diffraction and transmission electron microscopy. The results show that, an epitaxial Si layer with a low defect density can be grown. Epitaxial growth of thin crystalline layers on double-layer PSi can provide opportunities for silicon-on-insulator applications and Si-based solar cells provided that the epitaxial layer has a sufficient crystallographic quality

Propriétés structurales, mécaniques et optiques des polymères semi-conducteurs conjugués déposés sur substrat extensible

L'énergie solaire photovoltaïque (PV) est en plein essor partout dans le monde, car elle représente une alternative aux énergies fossiles et nucléaires. De nombreux travaux concernent aujourd'hui le développement de cellules solaires photovoltaïques bas coût. Les technologies en couches minces telles que les cellules solaires organiques à base de polymères semi-conducteurs permettent de répondre à cette problématique grâce à une réduction des quantités de matières et à l'utilisation de procédés de réalisations bas coûts. D'autre part, l'utilisation d'un support souple ou même extensible ouvre de nouvelles applications dans les domaines du divertissement, du sport ou de la santé. Cependant, le lien entre le transport de charges ou les propriétés optiques avec l'ordre structural des polymères est encore peu exploré, et en particulier le comportement de ces propriétés sous contrainte doit être abordé. Ce travail se situe dans le cadre d'une thèse en cotutelle entre les équipes du laboratoire L3M à l'Ecole Nationale Supérieure des Mines et de la Métallurgie d'Annaba en Algérie et l'IM2NP à Aix-Marseille Université en France. L'objectif est de comprendre le comportement mécanique des matériaux organiques semi-conducteurs (déformation, plasticité, modification des propriétés électriques ou optiques) par des mesures couplées. Cela permettra d'améliorer leur fonctionnement et leur durée de vie ainsi que de connaître les limites en termes de contraintes appliquées afin d'optimiser leur utilisation. Nous étudions dans un premier temps des films minces de polymères semi-conducteurs (P3HT et PTB7 choisis pour leur bon rendement), avant de pouvoir adapter par la suite les méthodes de mesure à des empilements de matériaux pour le photovoltaïque. Le dépôt de ces matériaux organiques sur des supports flexibles voire même extensibles est une étape clé du travail. Nous utiliserons pour cela les techniques de drop-casting et de spin-coating, mais aussi par la suite l'impression par jet d'encres pour structurer les matériaux déposés. Des électrodes métalliques sont également déposées afin de pouvoir étudier conjointement les propriétés de conductivité électrique. Les propriétés structurales ont été étudiées par diffraction des rayons X en incidence rasante au synchrotron, sur la ligne de lumière BL9 à Delta (Dortmund) et la ligne DiffAbs du synchrotron Soleil à Paris. Les modifications de structure ont été mesurées, et cela sous des élongations importantes (jusqu'à 20 %). Des mesures des propriétés optiques par ellipsométrie spectroscopique, sous traction seront effectuées au laboratoire IM2NP, afin de corréler les propriétés physiques de ces matériaux organiques. Ces mesures seront complétées par des investigations en microscopie électronique à balayage, qui se feront au laboratoire L3M

Structure and charge transport anisotropy of polythieno[3,4- b ]-thiophene- co -benzodithiophene (PTB7) oriented by high-temperature rubbing

International audienceStructure determination in high performance polymer semiconductors such as polythieno[3,4‐b]‐thiophene‐co‐benzodithiophene (PTB7) is essential to establish proper structure–property correlations. A combination of high‐temperature rubbing and isothermal crystallization leads to oriented and crystalline films of face‐on oriented PTB7 crystals. Electron diffraction indicates that crystallinity is marginal in the rubbed films but develops upon postrubbing annealing at T ≥ 250 °C. The best oriented and crystalline PTB7 films have a dichroic ratio of 12 for UV–vis absorption. The hole mobilities are improved by a factor of six along the rubbing direction over nonaligned films (µ// = 5.8 × 10$^{−3}$ cm$^2$ V$^{−1}$ s$^{−1}$ vs µ⊥ = 3.1 × 10$^{−4}$ cm$^2$ V$^{−1}$ s$^{−1}$). Structural analysis yields three possible models that share similar structural features, however; namely (i) PTB7 chains form a layered packing such as poly(2,5‐bis(3‐dodecyl‐2‐yl)thieno[3,2‐b]thiophene) with $\pi$‐stacked backbones alternating with layers of strongly interdigitated alkyl side chains, (ii) the PTB7 chains adopt a nonplanar zigzag conformation, and (iii) PTB7 chains show a mixed stacking of thieno[3,4‐b]thiophene and benzodithiophene blocks. Overall, these results highlight the key role played in polymer semiconductor crystals by the steric constraints due to the branched alkyl side chains interdigitation on the π‐stacking of conjugated backbones

Time-resolved piezoelectric response in relaxor ferroelectric (Pb0.88La0.12)(Zr0.52Ti0.48)O3 thin films

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In-situ characterization of thermomechanical behavior of copper nano-interconnect for 3D integration

Hybrid bonding is a very promising 3D packaging technology which allows extremely high interconnect density between electronic chips. In its most advanced interconnect pitch, Cu pads as small as 300 nm may be used. Successful bonding relies directly on the thermomechanical displacement of Cu above the oxide matrix. Hence, the control of this technology relies on a profound understanding of the thermomechanical behavior of 300 nm Cu pads. To achieve this goal, X-ray synchrotron Laue micro-diffraction is used to monitor the strain state and orientation of individual Cu pads in situ during heat treatment. The experimental findings are completed with Finite Element Modeling simulations including elastic anisotropy and plastic behavior. The 300 nm Cu pads are found monocrystalline with random lattice orientations. The thermomechanical behavior of each pad is found highly driven by its crystal orientation in accordance with the elastic and plastic anisotropy of copper. Very good agreement is found with simulations offering profound understanding of the single nanocrystalline Cu grains properties and providing solid conclusions for a successful hybrid bonding at sub-micrometric pitch level.NANOELE

Shear loading of FCC/BCC Cu/Nb nanolaminates studied by in situ X-ray micro-diffraction

International audienceFace-centered cubic/body centered cubic (FCC/BCC) nanolaminates prepared by Accumulative Roll Bonding (ARB) have been extensively studied because of their unique mechanical properties. Recently, micro-beam bending experiments, performed on Cu/Nb ARB samples, have shown an anisotropic interface sliding behavior linked to the strong in-plane texture. To test interface sliding on a macroscale we have developed a shear test based upon a specific sample geometry and on in situ tensile loading on an X-ray synchrotron beamline. As received nanolaminate samples exhibit a very anisotropic crystallographic texture as expected from the fabrication process. In situ X-ray diffraction in the sheared zone during mechanical loading yields strains in Cu and Nb. Early brittle failure prevents investigating further the sliding at interfaces. This is probably caused by crack initiation from the inner surfaces of the notches used to induce shear

Crystallographic Anisotropy Dependence of Interfacial Sliding Phenomenon in a Cu(16)/Nb(16) ARB (Accumulated Rolling Bonding) Nanolaminate

International audienceNanolaminates are extensively studied due to their unique properties such as impact resistance, high fracture toughness, high strength, and resistance to radiation damage. Varieties of nanolaminates are being fabricated to achieve high strength as well as fracture toughness. In this study, one such nanolaminate fabricated through accumulative roll bonded (Cu(16)/Nb(16) ARB nanolaminate, where 16 nm is the layer thickness) is used as a test material. Cu(16)/Nb(16) ARB nanolaminate exhibits crystallographic anisotropy due to the existence of distinct interfaces along the rolling direction (RD) as well as the transverse direction (TD). Nanoindentation was executed using a Berkovich tip with the main axis oriented either along TD or RD of Cu(16)/Nb(16) ARB nanolaminate. Subsequently, height profiles were obtained along the main axis of the Berkovich indent for both TD and RD using scanning Probe Microscopy (SPM), which was later used to estimate the pile-up along RD and TD. TD exhibited more pile-up than RD due to the anisotropy of Cu(16)/Nb(16) ARB interface and material plasticity along TD and RD. An axisymmetric 2D finite element analysis (FEA) was also performed to compare/validate nanoindentation data such as load vs. displacement curves, and pile-up. The FEA simulated load vs. displacement curves matched relatively well with the experimentally generated load-displacement curves, while qualitative agreement was found between simulated pile-up data and experimentally obtained pile-up data. The authors believe that pile-up characterization during indentation is of great importance to documenting anisotropy in nanolaminates

Berkovich nanoindentation study of 16 nm Cu/Nb ARB nanolaminate: Effect of anisotropy on the surface pileup

International audienceNanoindentation is widely used to investigate elastic modulus, hardness and work hardening behaviour of nano- and micro-scale laminates. In this work, 16 nm accumulative roll bonding (ARB) Cu/Nb nanolaminate is used as a test material due to its interfacial anisotropy owing to the presence of contrasting interfaces along rolling (RD) and transverse direction (TD). Nanoindentation was performed along TD as well as RD of ARB Cu/Nb nanolaminate, and then scanning probe microscopy (SPM) data were collected to measure the pileup along RD and TD. Nanolaminate along RD was found to show higher surface pileup than TD which is attributed to crystallographic and interfacial anisotropy resulting in (a) higher yield strength (low plasticity) along TD in comparison to RD and (b) high interfacial sliding in the case of TD resulting in less co-deformation of layers in comparison to RD. The characterization of surface pileup is of significant importance for facilitating the study of anisotropic micro/nanolaminates