Samuel Tardif

Atomic Energy and Alternative Energies Commission | CEA · Institut de recherche interdisciplinaire de Grenoble (IRIG)

The sustainable production of hydrogen as well as its re-conversion into electricity will be a key aspect in a future green energy environment that is depending on regenerative resources. In order to ensure the eminent position of solid oxide cells (SOC) in this future hydrogen economy their reliability and long-term performance still needs to be i...

In the quest for high-capacity Li-ion batteries, moving from classical intercalation reactions such as those occurring at graphite-based electrodes to alloying reactions is a promising alternative. Among active materials which form alloys upon lithiation, silicon is a good candidate thanks to its high theoretical capacity, although it shows limited...

With the advent of high-brilliance synchrotron sources, the issue of beam damage on the samples deserves proper attention. It is especially true for operando studies in batteries, since the intense photon fluxes are commonly used to probe ever finer effects. Here we report on the causes and consequences of synchrotron X-ray beam damage in batteries...

With the advent of high brilliance 4th generation synchrotron sources, the issue of beam damage on the samples cannot be ignored and deserves a wide attention. It is especially true for operando studies in batteries, since the intense photon fluxes are commonly used to probe ever finer effects. Here we report on a quantitative study on the causes a...

A versatile industrial recipe of transferring nitride microelectronic components such as micro‐electromechanical systems (MEMS) onto flexible and stretchable substrates is demonstrated. This method bypasses difficulties of temperature‐related processing, and is applicable to large‐scale and mass production. The technological process of fabrication...

The polyvinylidene fluoride trifluoroethylene P(VDF-TrFE) copolymer is polymorphic with two main phases called α (paraelectric) and β (ferroelectric). Effects of annealing, cooling, and poling on the phase transitions are studied in thin films. More precisely, the α-β structural transition is investigated in copolymer capacitors with flexible elect...

A feed-forward neural-network-based model is presented to index, in real time, the diffraction spots recorded during synchrotron X-ray Laue microdiffraction experiments. Data dimensionality reduction is applied to extract physical 1D features from the 2D X-ray diffraction Laue images, thereby making it possible to train a neural network on the fly...

In situ investigations of cracks propagating at up to 2.5 km s ⁻¹ along an (001) plane of a silicon single crystal are reported, using X-ray diffraction megahertz imaging with intense and time-structured synchrotron radiation. The studied system is based on the Smart Cut process, where a buried layer in a material (typically Si) is weakened by micr...

To explore an effective route of customizing the superelasticity (SE) of NiTi shape memory alloys via modifying the grain structure, binary Ni55Ti45 (wt) alloys were fabricated in as-cast, hot swaged, and hot-rolled conditions, presenting contrasting grain sizes and grain boundary types. In situ synchrotron X-ray Laue microdiffraction and in situ s...

Germanium is a promising active material for high energy density anodes in Li-ion batteries thanks to its good Li-ion conduction and mechanical properties. However, a deep understanding of the (de)lithiation mechanism of Ge requires advanced characterizations to correlate structural and chemical evolution during charge and discharge. Here we report...

Ever since the very first human-made knapped tools, the control of fracture propagation in brittle materials has been a vector of technological development. Nowadays, a broad range of applications relies on crack propagation control, from the mitigation of damages, e.g., from impacts in glass screens or windshields, to industrial processes harnessi...

Understanding ionic solutions in single-digit nanoconfinement is crucial to explain the behavioral transition of confined solutions. This is particularly the case when the system length scale crosses the classical key length scales describing energetics and equilibrium of ionic solutions next to surfaces. Experimentally probing nanoconfinement woul...

A scalable manufacturing method is demonstrated for the transfer of crystalline AlN thin-films deposited on 200 mm Si wafer onto a flexible and stretchable polymer. The resulting AlN-On-Polymer (AOP) can be bent and stretched. This novel transfer process allows a straightforward strain-engineering method of semiconductor thin-films when transferred...

Vibrations induced by crack propagation in a strip of bonded silicon wafers are studied. A new optical setup enables the fast recording of crack-originated acoustic waves, emitted both ahead and behind the crack front, in bonded and separated wafers, respectively. Three types of crack-induced vibrations are identified, corresponding to different ex...

Geopolymer has been selected as a hydraulic mineral binder for the immobilization of MgZr fuel cladding coming from the dismantling of French Uranium Natural Graphite Gas reactor dedicated to a geological disposal. In this context, the corrosion processes and the nature of the corrosion products formed on MgZr alloy in a geopolymer matrix with and...

The interactions of a moving crack with self-emitted acoustic waves are studied in ion-implanted circular plates of crystalline silicon, where complex reproducible surface patterns made of local roughness variations are observed. A simple geometrical model, considering the sole propagation of A0 Lamb waves inside the assembly, allows full predictio...

High Sn-content Ge1-xSnx alloys are excellent candidates for the fabrication of electronic and optoelectronic monolithically integrated devices on CMOS platforms. The fabrication of high performance devices requires high quality GeSn layers free of Sn precipitates. This work reports on the characterization of GeSn layers and micro-disk lasers with...

Heterogeneous potential and lithium distribution inside lithium ion batteries highly affect their performance and durability. In particular, increased lithium gradients are expected in thick electrodes with high energy densities or cycling at high currents. To optimise electrodes and cells designs, it is thus crucial to predict and probe the local...

This study reports the manufacturing of Silicon On Polymer (SOP). It describes the transfer of a 200 mm diameter silicon thin film from a silicon on insulator (SOI) substrate to a flexible polymer. The thickness of the single-crystal silicon film was less than 200 nm and the transfer was achieved by bonding the SOI wafer to a temporary silicon carr...

High temperature (>1000°C) annealing is necessary to completely close a bonding interface. Using interface synchrotron high energy X-ray reflectivity, we have investigated the sealing behavior of silicon thermal oxide/ silicon thermal oxide interfaces, with different surface roughnesses. Interface X-ray reflection is able to measure accurately the...

Strain engineering can be called upon to tune the band structures of semiconductors. It is widely used in different types of microelectronics devices and it is expected to enable unprecedented responses in optoelectronics [1]. In the case of single crystal Silicon (sc-Si), several approaches have been proposed, relying either on the lattice mismatc...

Advanced anode material designs utilizing dual phase alloy systems like Si/FeSi2 nano-composites show great potential to decrease the capacity degrading and improve the cycling capability for Lithium (Li)-ion batteries. Here, we present a multi-scale characterization approach to understand the (de-)lithiation and irreversible volumetric changes of...

Tensile strained GeSn lasers could be used as tunable infrared light sources in silicon photonics. We explore here the relationship between the uniaxial tensile strain applied to suspended microbridges and the maximum lasing temperature reached in GeSn 13% cavities.

While intensive efforts have been devoted to studying the nature of the solid-electrolyte interphase (SEI), little attention has been paid to understanding its role in the mechanical failures of electrodes. Here we unveil the impact of SEI inhomogeneities on early-stage defect formation in Si electrodes. Buried under the SEI, these early-stage defe...

Distributions of potential and lithium content inside lithium ion batteries highly affects their performance and durability. An increased heterogeneity of the lithium distribution is expected in thick electrodes with high energy densities or cycling at high currents. To optimize electrodes and cells designs, it is crucial to probe lithium concentra...

Failure mechanisms associated with silicon-based anodes are limiting the implementation of high-capacity lithium-ion batteries. Understanding the aging mechanism that deteriorates the anode performance and introducing novel-architectured composites offer new possibilities for improving the functionality of the electrodes. Here, the characterization...

We describe a process for transferring a 200 nm thick, 200 mm wide monocrystalline silicon (mono c-Si) thin film from a Silicon-On-Insulator (SOI) onto a flexible polymer substrate. The result is a stretchable and flexible ultra-thin semi-conductor film that can be subjected to tensile stress experiments. The process uses off-the-shelf 200 mm wafer...

The Cover Feature shows the chemical mapping of SiGe@Si core‐shell nanoparticles, demonstrated for the first time, and the reactor used to synthesize them using laser pyrolysis method. The original Si−Ge structure illustrated here is linked to the remarkable performance (capacity and stability) of the nanoparticles as anode of Li‐ion batteries.More...

The (de)lithiation process and resulting atomic and nanoscale morphological changes of an a-Si/c-FeSi2/graphite composite negative electrode are investigated within a Li-ion full cell at several current rates (C-rates) and after prolonged cycling by simultaneous operando synchrotron wide-angle and small-angle X-ray scattering (WAXS and SAXS). WAXS...

Silicon‐germanium nanostructures are promising anode materials for high stability, high capacity and fast cycling Li‐ion batteries. We report here on the outstanding performance of original SiGe/Si core@shell nanoparticle heterostructures synthetized in one step by laser pyrolysis of silane and germane. By tuning the gas ratio, the alloy compositio...

Combined with renewable energy harvesting technologies, such as solar panels or wind turbines, energy storage is the key to keeping up with the ever-increasing demand for electric energy and reducing the world dependency on fossil fuels. Over the last three decades lithium-ion batteries (LiBs), starting with the first commercialized cell by Sony in...

The impact of nanoconfinement on the microstructure of alkoxysilane layers grafted by supercritical CO2 was determined using model system made of silica nanochannels, i.e. planar silica surface spaced of few nanometers. Two type of silica nanochannels of 3 and 5 nm gap size were grafted with alkoxysilanes having different head groups (thiol, amine,...

The interaction of a propagating crack in implanted silicon with self-emitted acoustic waves results in periodic patterns on fractured surfaces. Direct measurement of the acoustic emission ahead of the fracture front shows the emergence of dominant acoustic frequency related to the crack velocity. It is shown that the surface modifications are made...

Direct bonding interfaces exhibit, before annealing, a narrow density gap due to the contact interactions of facing surface asperities and their incomplete compression. This gap makes a narrow channel (width<1nm) along which water is able to move. This is evidenced clearly from the defect distribution in Si/Si hydrophilic bonding showing clearly a...

Due to an impressive and continuous improvement in performance, the use of lithium ion batteries (LiBs) has greatly increased since this technology was first commercialized by Sony in 1990 and is quickly spreading to more demanding applications. Today, LiBs are not only used to power portable electronic devices such as smartphones or laptops but al...

Chemical reactions occurring at the material–aqueous solution interface are controlled by an interfacial layer of a few nm where conceptual models such as the Electrical Double or Triple Layer models can be applied. These models describing the spatial distribution of ions in term of perpendicular distance from the planar surface and ignoring topogr...

Operando Raman spectroscopy and synchrotron X-ray diffraction were combined to probe the evolution of strain in Li-ion battery anodes made of crystalline silicon nanoparticles. The internal structure of the nanoparticles during two discharge/charge cycles was evaluated by analyzing the intensity and position of Si diffraction peaks and Raman TO-LO...

Lately, germanium based materials attract a lot of interest as they can overcome some limits inherent to standard Silicon Photonics devices and can be used notably in Mid-Infra-Red sensing applications. The quality of epitaxially grown intrinsic and doped materials is critical to reach the targeted performances. One of the main challenges in the fi...

The demonstration of a CMOS compatible laser working at room temperature has been eagerly sought since the beginning of silicon photonics. Although bulk Germanium (Ge) is an indirect bandgap material, Tin (Sn) can be incorporated into it to turn the resulting alloy into a direct band-gap semiconductor. Recently, lasing was demonstrated at cryogenic...

The application of high values of strain to Ge considerably improves its light emission properties and can even turn it into a direct band gap semiconductor. Raman spectroscopy is routinely used for strain measurements. Typical Raman-strain relationships that are used for Ge were defined up to ∼1% strain using phonon deformation potential theory. I...

Adding Tin (Sn) to Germanium (Ge) can turn it into a direct bandgap group IV semiconductor emitting in the mid-infrared wavelength range. Several approaches are currently being investigated to improve the GeSn devices. It has been theoretically predicted that the strain can improve their optical properties. However, the impact of strain on band par...

It is widely accepted that the band structure of germanium can be altered by tensile strain so as to reduce the energy difference between its direct and indirect band gaps. However, the conventional deformation potential model most widely adopted to describe this transformation happens to have been investigated only up to 1 % uniaxially loaded stra...

We report here on measurements demonstrating that water is able to enter a hydrophilic wafer bonding assembly from the edge. The driving forces for water entry are capillary forces driven by the negative Laplace pressure. The characteristic time for water to penetrate the interface is consistent with standard values for water viscosity and gap widt...

We describe here the sequence of evolution of defects after hydrogen alone or hydrogen plus helium implantation in silicon, from matrix incorporation up to microcracks formation. We detail the different steps of the process, concentrating on experimental results from X-ray scattering and IR microscopy observations

This study describes a process for transferring a 200 nm Si thin film from a SOI onto a flexible substrate. The objective is to find a way for applying a tensile strain onto a very thin semi-conductor film for tensile strain engineering. The processs is achieved with 200 mm wafers and based on a polymer temporary bonding process. Grinding and etchi...

The kinetics of water diffusion through the gap formed by the direct bonding of two silicon wafers is studied using two different techniques. X-ray reflectivity is able to monitor the interface density changes associated with the water front progression. The water intake is also revealed through the defect creation upon annealing, creating a rim-li...

Applying tensile strain on an undirect band gap semiconductor crystal is a very promising way to tune it into a direct band gap [1] , [2] . This basic feature can be an outstanding progress for the use of classical semiconductor as silicon or germanium in interesting optoelectronic applications [3] . One way to apply a tensile strain is to transfer...

We have studied the development of cracks in gas-implanted silicon, from nano-scale to wafer-scale which is at the heart of the SmartCut™ technology. We will discuss the results of X-ray scattering experiments that allow the monitoring of growth of nanometer-size cavities (platelets) from implantation to their full development where they reach size...

A bonding interface between wafers usually exhibits a narrow gap due to the imperfect compression and matching of the facing wafer surface asperities. When hydrophilic bonding is considered, this gap can be partly filled with water originating from the adsorbed water before bonding or entering the gap from the surrounding atmosphere when bonded. Th...

Applying a large tensile strain of several percent in a Ge layer is promising in order to improve its optical properties and possibly turn germanium into an efficient CMOS compatible light emitter. Several approaches are currently being explored for high strain induction into Ge [1-4]. Since biaxial or uniaxial stress inductions are interesting, we...

Using the Smart Cut TM technology, we fabricated 200 mm optical Germanium-On-Insulator (GeOI) substrates for photonic applications. The high crystalline quality of the Ge layer opens the way to wafer-scale fabrication of photonic components such as new light emitting devices based on highly-tensile strain.

Cavity enhanced photoluminescence at a wavelength as long as 5 μm is obtained in uniaxial tensile strained GeOI micro-bridges. We show, using temperature dependent photoluminescence spectroscopy, a crossover to fundamental direct bandgap and reveal from a mode analysis the free carrier induced loss increase.

Ge under high strain is predicted to become a direct bandgap semiconductor. Very large deformations can be introduced using microbridge devices. However, at the microscale, strain values are commonly deduced from Raman spectroscopy using empirical linear models only established up to 1.2% for uniaxial stress. In this work, we calibrate the Raman-st...

Silicon is being considered as one of the most promising anode materials for next generation lithium-ion batteries due to its high theoretical capacity (3580 mA h g ⁻¹ at room temperature) (1). Upon charging, Si and Li react via an alloying process with a sharp interphase separating the growing Li x Si amorphous phase from the pristine crystalline...

Germanium is a strong candidate as a laser source for silicon photonics. Despite the indirect nature of its bandgap, the application of several percent of tensile strain reduces the energy difference between its direct and indirect bandgaps [1]. It has been predicted that above a certain strain threshold, germanium transforms into an actual direct...

Core-shell structural evolution of crystalline silicon nanoparticles upon lithiation/delithiation by ex situ Raman spectroscopy and operando synchrotron X-ray diffraction Silicon has attracted substantial attention as an alternative anode material for next-generation Li-ion batteries (LiBs) as it has a high theoretical capacity of 3580 mA h g ⁻¹ th...

Micro-Laue diffraction and simultaneous rainbow-filtered micro-diffraction were used to measure accurately the full strain tensor and the lattice orientation distribution at the sub-micron scale in highly strained, suspended Ge micro-devices. A numerical approach to obtain the full strain tensor from the deviatoric strain measurement alone is also...

Currently, one of the main challenges in the field of silicon photonics is the fabrication of efficient laser sources compatible with the microelectronic fabrication technology. An alternative to the complexity of integration of group III-V laser compounds is advancing from high tensile strains applied to germanium leading to improved emission prop...

We demonstrate the crossover from indirect- to direct band gap in tensile-strained germanium by temperature-dependent photoluminescence. The samples are strained microbridges that enhance a biaxial strain of 0.16% up to 3.6% uniaxial tensile strain. Cooling the bridges to 20 K increases the uniaxial strain up to a maximum of 5.4%. Temperature-depen...

The influence of pattern design and tensile strain on light emission was investigated in Ge layers and suspended membranes. The optical properties were examined by micro-photoluminescence and reflectivity. Tensile strain was extracted from micro-Raman spectroscopy. It has been shown that Fabry–Pérot interference fringes can dominate the photolumine...

High tensile strains in Ge are currently studied for the development of integrated laser sources on Si. In this work, we developed specific Germanium-On-Insulator 200 mm wafer to improve tolerance to high strains induced via shaping of the Ge layers into micro-bridges. Building on the high crystalline quality, we demonstrate bi-axial tensile strain...