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International audience; In this work, solid-state a-GeTe growth is studied during the reactive diffusion of a polycrystalline thin film of hexagonal Te deposited on an amorphous Ge thin film (Te-on-Ge) using in situ X-ray diffraction, in situ transmission electron microscopy, and atom probe tomography. After deposition, an amorphous intermixing layer is observed between the Te and Ge layers. a-GeTe is found to form a 2D layer between the deposited Ge and Te layers during growth, with a thickness increasing linearly with time as predicted by the linear-parabolic model for interfacial reaction limited growth. The activation energy of nucleation and interfacial reactions was determined from different isothermal annealing. The obtained results are compared to the observations previously reported during a-GeTe 3D growth in a sample made of an amorphous Ge layer deposited on a polycrystalline Te layer (Ge-on-Te) in the same magnetron sputtering system under the same conditions.

International audience; Hydrogen passivation of silicon dangling bonds is a key requirement in the realization of reliable CMOS devices. The creation of a hydrogen reservoir in the device near the silicon may be a solution supporting constant passivation during the life-cycle of the device. In this work, we used thermal desorption spectroscopy to evaluate the amount of hydrogen stored in undoped silicon glass (USG) deposited using SiH4 (USG-SiH4) or tetraethyl orthosilicate (USG-TEOS), and silicon (carbon) nitrides, typical dielectrics used in CMOS technology. The goal of the study is to determine if these materials can be used as hydrogen source or diffusion barrier. Our results suggest that USG-SiH4 can act as an efficient source of hydrogen, while Si nitrides can act as reliable diffusion barrier.

α-MgAgSb is a tellurium-free thermoelectric material that exhibits good thermoelectric properties near room temperature. Being made of relatively abundant elements compatible with the complementary metal oxide semiconductor (CMOS) technology, it is considered as a possible solution for the development of high-efficiency thermoelectric devices for heat waste harvesting in microelectronic setups. This study presents a first attempt to investigate the structural properties of MgAgSb thin films prepared by solid-state reactive diffusion. X-ray diffraction (XRD) was used to follow phase formation in thin films, first, in the case of the binary Ag3Sb and Mg3Sb2 compounds, and then, in the case of the ternary system Mg-Ag-Sb. For the later, in situ XRD was used to follow real-time phase formations during the reaction of the bilayerAg3Sb/Mg3Sb2. The results show that the phase α-MgAgSb can be produced by reactive diffusion at the interface of the bilayer. Furthermore, the three phases α, β, and γ are shown to coexist at 360 °C, which can be the result of the thin film geometry (surface and interface effects) or due to a different stoichiometry between these three phases contrasting with usual belief. At temperatures higher than 450 °C, γ-MgAgSb is the only phase stabilized in the film. This study serves as a benchmark for the production of pure α-MgAgSb thermoelectric thin films by reactive diffusion.

International audience; α-MgAgSb thin films are expected to be compatible with the complementary metal oxide semiconductor (CMOS) technology, and could be used to develop thermoelectric modules integrated to microelectronic devices for energy harvesting. However, bulk studies showed that the presence of secondary phases in addition to α-MgAgSb, such as the metallic phase Ag 3 Sb, deteriorates the thermoelectric properties. Consequently, understanding phase transformations in Mg-Ag-Sb thin films produced by CMOS-compatible magnetron sputtering is capital for the production of homogeneous α-MgAgSb thin films to be used in energy harvesting thermoelectric modules integrated into microelectronic devices. In this work, different Mg-Ag-Sb films were deposited by magnetron sputtering using either a single alloyed target with the average composition Mg 1/3 Ag 1/3 Sb 1/3 or using Mg, Ag, Sb co-deposition from three elementary targets. In situ X-ray diffraction measurements were used to investigate the phase transitions in the films, aiming to determine the thermal stability of α-MgAgSb and to investigate the possibility of producing α-MgAgSb films without secondary phases. The results show that the use of the single alloyed target does not allow the production of homogenous α-MgAgSb films. The phase formation sequence observed in the films is different from bulk samples in this case. Co-sputtering of the three elements Mg, Ag, and Sb, allowing the composition of the as-deposited film to be better controlled, confirmed that the Mg 1/3 Ag 1/3 Sb 1/3 stoichiometry does not allow the production of homogenous α-MgAgSb films. Contrasting with usual belief, the results show that the Ag and Sb compositions of the phases α-MgAgSb and γ-MgAgSb vary during annealing, and the phase transitions α-to-β, β-to-γ, and α-to-γ are not allotropic. These finding are of major importance for the production of the thermoelectric compound α-MgAgSb, and explain the large variations of the α-MgAgSb Seebeck coefficient reported in the literature.

International audience; The structure, the chemistry, and the magnetic properties of MnCoGe thin films elaborated by reactive diffusion were investigated. In situ X-ray diffraction (XRD) was used to study phase formation during thin film reaction. MnCo, MnGe, and CoGe binary systems were studied before investigating phase formation during Mn-Ge-Co ternary system reaction. Three pure layers of Mn, Ge, and Co were successively deposited by magnetron sputtering on SiO2 to form a 200 nm-thick Co/Ge/Mn stack, and annealed. Six phases were observed during reaction, first following the sequential phase formation observed for the binary systems at the two Mn/Ge and Ge/Co interfaces, and ending with the formation of a single ternary compound MnCoGe at 673 K. The structure and the composition of the MnCoGe films were characterized using XRD, atomic force microscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy. The magnetic properties of the films were studied using superconducting quantum interference device (SQUID) and ferromagnetic resonance (FMR) measurements. The obtained MnCoGe thin films are polycrystalline with the stoichiometric composition Mn:Co:Ge(1/3:1/3:1/3), and show high porosity. They are made of grains exhibiting both the Ni2In-type hexagonal structure and the TiNiSi-type orthorhombic structure.

International audience; We have studied the stability of manganese germanide thin films grown on Ge(111) substrates by three different growth methods: solid phase epitaxy, reactive deposition epitaxy and co-deposition. By combining X-ray diffraction and magnetic measurements, we demonstrate that we can form either Mn5Ge3 or Mn11Ge8 thin films depending on the growth processes. In the case of solid phase epitaxy, we explain the phase formation sequence by taking into consideration the kinetic and thermodynamic processes involved. Tuning phase formation of the manganese germanide thin films was determined using in situ X-ray diffraction and the effect of the thin film thickness on the Mn5Ge3 thermal stability was investigated.

International audience; The compound GeTe, despite its simple stoichiometry, is rather unconventional and has been investigated both from a fundamental and technological perspective: it is of high interest for several technologies such as data-storage (phase change memories) and thermoelectricity. The understanding of GeTe growth is thus a key issue for technological applications and fundamental understanding. In this work, GeTe crystallization kinetics is compared to Ge/Te reactive diffusion kinetics using in situ X-ray diffraction measurements, as well as in situ transmission electron microscopy. GeTe crystallization from an amorphous solid solution exhibiting the stoichiometry of the compound GeTe is found to occur at the same temperature as for the reactive diffusion of an amorphous Ge layer on top of a polycrystalline Te layer. Furthermore, GeTe growth is of tridimensional type in the two cases, and can be modeled by the Johnson-Mehl-Avrami-Kolmogorov model. Using this model, the activation energies of nucleation and growth were determined for both crystallization and reactive diffusion. The results suggest that GeTe exhibits nucleation/reaction kinetics unusually low compared to atomic transport kinetics, contrasting with other germanides.

Dislocation engineering in crystalline materials is essential when designing materials for a large range of applications. Segregation of additional elements at dislocations is frequently used to modify the influence of dislocations on material properties. Thus, the influence of the dislocation elastic field on impurity segregation is of major interest, as its understanding should lead to engineering solutions that improve the material properties. We report the experimental study of the elastic field influence on atomic segregation in the core and in the area surrounding edge dislocations in Fe-based alloys. Each element is found either to segregate in the edge dislocation core or to form atmospheres. The elastic field has a strong effect on the segregation atmosphere, but no effect on the dislocation core segregation. The theory is in good agreement with experiments, and should support dislocation engineering.

The semi-conductor Ge1―xSnx exhibits interesting properties for optoelectronic applications. In particular, Ge1―xSnx alloys with x ≥ 0.1 exhibit a direct band-gap, and integrated in complementary-metal-oxide-semiconductor (CMOS) technology, should allow the development of Si photonics. CMOS-compatible magnetron sputtering deposition was shown to produce monocrystalline Ge1―xSnx films with good electrical properties at low cost. However, these layers were grown at low temperature ( 600 K) on Si(001) by magnetron sputtering in order to produce low-cost and CMOS-compatible relaxed pseudo-coherent layers with x ≥ 0.1 exhibiting a better crystallinity. Ge1―xSnx crystallization and Ge1―xSnx crystal growth were investigated. Crystallization of an amorphous Ge1―xSnx layer deposited on Si(001) or Ge(001) grown on Si(001) leads to the growth of polycrystalline films. Furthermore, the competition between Ge/Sn phase separation and Ge1―xSnx growth prevents the formation of large-grain Sn-rich Ge1―xSnx layers without the formation of β-Sn islands on the layer surface, due to significant atomic redistribution kinetics at the crystallization temperature (T = 733 K for x = 0.17). However, the growth at T = 633 K of a highly-relaxed pseudo-coherent Ge0.9Sn0.1 film with low impurity concentrations (

The heat-affected zone (HAZ) of the low-alloy steel in dissimilar metal welds has been investigated by electron backscatter diffraction, scanning electron microscopy and atom probe tomography. The welding process generates a temperature gradient, creating two zones in the HAZ: a carbon depleted zone and a carbon non-depleted zone (NDZ). The evolution of the microstructure in the NDZ and the atomic distribution at the ferrite/ferrite and ferrite/cementite interfaces was investigated for different long-term thermal ageing conditions. Many alloying elements segregate to grain boundaries (ferrite/ferrite interfaces) with a different amount in relation to the misorientation of the grain boundaries, but only phosphorus (P) segregates to the ferrite/cementite interface. In addition, the amount of P segregation increases with the increase in temperature and ageing time and depends also on the structural parameters of the interface. The partitioning between cementite and ferrite phases presents a slight evolution with long-term thermal ageing, related to kinetic limitation.

Nanostructures used to build current technology devices are generally based on the stack of several thin films (from few nanometer-thick to micrometer-thick layers) having different physical properties (conductors, semiconductors, dielectrics, etc.). In order to build such devices, thin film fabrication processes compatible with the entire device fabrication need to be developed (each subsequent process step should not deteriorate the previous construction). Solid-state reactive diffusion allows thin film exhibiting good interfacial properties (mechanical, electrical…) to be produced. In this case, the film of interest is grown from the reaction of an initial layer with the substrate on which it has been deposited, during controlled thermal annealing. In the case of the reaction of a nano-layer (thickness < 100 nm) with a semi-infinite substrate, nanoscale effects can be observed: i) the phases appear sequentially, ii) not all the thermodynamic stable phases appear in the sequence (some phases are missing), and iii) some phases are transient (they disappear as fast as they appear). The understanding of the driving forces controlling such nanoscale effects is highly desired in order to control the phase formation sequence, and to stabilize the phase of interest (for the targeted application) among all the phases appearing in the sequence.This chapter presents recent investigations concerning the influence of atomic transport on the nanoscale phenomena observed during nano-film reactive diffusion. The results suggest that nano-film solid-state reaction could be controlled by modifying atomic transport kinetics, allowing current processes based on thin-film reactive diffusion to be improved.

PdGe contact fabrication on Ge(001) wafers doped with Ga is investigated using conventional complementary metal-oxide-semiconductor processes. Despite a p-type doping level of ~1.4 × 1020 cm−3, the resistivity of the PdGe contact is found to be twice higher than that of undoped Ge. Ga doping has no influence on the Pd reaction with Ge. However, the doping process and the Salicide process led to the formation of Ga-Pd defects in both sides of the PdGe/Ge interface, resulting from Ga and Pd co-segregation on Ge dislocation loops.

International audience; Mg-Ag-Sb thin films were deposited by magnetron sputtering using a commercial Mg 1/3 Ag 1/3 Sb 1/3 target. All the films contain principally the two phases Ag 3 Sb and alpha-MgAgSb in same proportions but exhibit different microstructures. The films have the same Seebeck coefficient despite the difference of interface density and structure. Theoretical calculations show that the film effective Seebeck coefficient S is depending only on the volume of each phase present in the film and their Seebeck coefficients. The multiple interfaces between the different phases have no effect on S .

International audience; High resolution imaging by secondary ion mass spectrometry and atom probe tomography have been employed to investigate boron segregation at austenite grain boundaries (γ GBs) after soaking in a high-strength low-carbon steel. The combined use of these two analytical techniques is shown to be powerful for quantifying solute and segregated boron levels. Quenching was performed after soaking aiming to clarify the temperature effect on boron distribution under thermal equilibrium. Boron depletion in the γ GBs vicinity was observed in the as-quenched states from high temperatures, suggesting that the cooling rate was not fast enough to limit boron diffusion during cooling. We found that boron segregation at γ GBs increases with temperature. This is due to the increase of solute boron concentration in the grains, resulting from boride precipitate dissolution. It appears that the segregation magnitude still follows the equilibrium laws as a function of temperature. From our investigations, it was possible to determine the boron equilibrium segregation enthalpy. These results have important practical consequences for controlling the levels of segregated boron in steels.

Carbon-doped Mn5Ge3 thin films were grown using magnetron sputtering and reactive diffusion or non-diffusive reaction (NDR). The C content, the Curie temperature, and the resonance field difference between the hard and easy axis were measured for all the films, allowing linear relations between these three parameters to be quantitatively determined. Thanks to these functions, the measurement of a single of these parameters allows the two others to be known. The association of the sputtering technique to the NDR process appears as the best way for producing C-doped Mn5Ge3 thin films.

For a long time, secondary ion mass spectrometry (SIMS) was the only technique allowing impurity concentrations below 1 at% to be precisely measured in a sample with a depth resolution of few nanometers. For example, SIMS is the classical technique used in microelectronics to study dopant distribution in semiconductors and became, after radiotracers were forsaken, the principal tool used for atomic transport characterization (diffusion coefficient measurements). Due to the lack of other equivalent techniques, sometimes SIMS could be used erroneously, especially when the analyzed solute atoms formed clusters, or for interfacial concentration measurements (segregation coefficient measurements) for example. Today, concentration profiles measured by atom probe tomography (APT) can be compared to SIMS profiles and allow the accuracy of SIMS measurements to be better evaluated. However, APT measurements can also carry artifacts and limitations that can be investigated by SIMS. After a summary of SIMS and APT measurement advantages and disadvantages, the complementarity of these two techniques is discussed, particularly in the case of experiments aiming to measure diffusion and segregation coefficients.

Ge and B diffusion was studied in nanocrystalline Si, and Pd and Si self-diffusion was studied in nanocrystalline Pd2Si during and after Pd/Si reactive diffusion. These experiments showed that grain boundary (GB) diffusion kinetic is the same in micro-and nanoGBs, whereas triple junction (TJ) diffusion is several orders of magnitude faster than GB diffusion. In addition, GB segregation and GB migration can significantly modify atomic diffusion profiles in nanocrystalline materials, and atomic transport kinetics can be largely increased in nanograins compared to micro-grains, as well as during reactive diffusion, probably due to an increase of point defect concentration. These observations show that atomic transport in nanometric layers during reactive diffusion is complex, since GBs and TJs are moving and the proportion of GBs and TJs is changing during the layer growth.

International audience; MnCoGe thin films were produced using simultaneous magnetron sputtering of Mn, Co, and Ge on SiO2, followed by non-diffusive reaction. The MnCoGe compound begins to form at ∼588 K, and structural characterizations show that the obtained MnCoGe film is polycrystalline with the hexagonal Ni2In-type structure. This structure is found to be stable from 873 K down to room temperature, the expected hexagonal/orthorhombic structural transition being prevented. The film exhibits a lower average Mn composition than the standard MnCoGe stoichiometry. Furthermore, small clusters (

International audience; The influence of stress on the distribution of slow-diffusing substitutional impurities in the vicinity of a dislocation loop in Si and Ge bulk was theoretically investigated, at the atomic scale, using the Si and Ge Stillinger-Weber potentials via Monte Carlo and kinetic Monte Carlo simulations. The dislocation loop was modeled by an extra atomic plane introduced between two (111) planes. The calculations were performed at high temperature, for which impurity diffusion was enabled. The influence of atomic size effect on Cottrell atmosphere formation was investigated considering the difference of atomic volume between Si and Ge. The dislocation loop elastic field was found to prevent the accumulation of substitutional atoms in the vicinity of the dislocation. However, the calculations suggest that substitutional impurities can occupy interstitial sites close to the dislocation loop. In this case, the elastic field surrounding the dislocation loop can promote Cottrell atmosphere formation mainly if the impurity exhibits a larger atomic radius than the matrix atoms (Si or Ge). (C) 2015 Elsevier B.V. All rights reserved.

The formation of voids on the surface of heavily implanted germanium has been known for more than 30 years. Recently there is a renewed interest in germanium due to its potential application in the complementary metal oxide semiconductor (CMOS) devices. Here we report the observation of germanium oxide microcrystals formed on the surface of tellurium implanted into a germanium substrate. The Ge target used was a (1 0 0) polished single crystalline germanium wafer and the implantation was carried out at room temperature with Te ions at 180 keV and a fluence of 3.6 × 1015 at/cm2. Under scanning electron microscope (SEM), the surface of the Ge substrate is evenly covered by microcrystals with a diameter about 1–2 μm and a coverage density of ∼107 particles/cm2. The initially smooth surface of the polished germanium substrate becomes very rough and mostly consists of voids with an average diameter of 40–60 nm, which is consistent with reports of heavily implanted germanium. The composition of the microcrystals was studied using energy dispersive X-ray analysis (EDX) and atom probe tomography (APT) and will be presented. Preliminary results indicate that tellurium is not detected in the microcrystals. The origin of the microcrystals will be discussed.

The behaviour of Fe atoms at the Si/SiO2 interface, as a modelisation of an involuntary Fe contamination before or during the oxidation process has been studied in Fe-implanted wafers. As-implanted and oxidized wafers were characterized by SIMS, APT, HR-TEM and STEM-HAADF. Successive steps of Fe segregation, iron-silicide precipitation and dissolution were identified. As expected for such a temperature range, the iron-silicide precipitates adopt the FeSi2 structure. Fe enriched phases were also identified in an advanced step of precipitation. Dynamic mechanisms are proposed, taking into account the competitive oxidizing of precipitates and silicon matrix, to understand the different steps and precipitation phases observed in the samples during the non-equilibrium conditions due to the oxide layer growth. The correlation between the formation of characteristic pyramidal defects at the SiO2/Si interface and the presence of the Fe-rich precipitates is explained. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In this paper, we report investigations concerning the fabrication of a diluted Ge (Mn) solution using solid state Mn diffusion, and Mn/Ge reactive diffusion for spintronic applications. The study of Mn diffusion shows that the quasi-totality of the incorporated Mn atoms occupies Ge substitutional sites and probably exhibits two negative elementary charges. The solubility limit of Mn in Ge is comprised between 0.7 and 0.9 % (T  600 °C). We show that substitutional Mn atoms are not ferromagnetic in Ge and consequently that Ge (Mn) diluted magnetic semiconductor can not be produced. Beside the ferromagnetic signal from Mn5Ge3, ferromagnetic signals detected in the samples could be always attributed to surface or bulk Mn-Ge clusters. Furthermore, we show that the CMOS Salicide process is potentially applicable to Mn5Ge3 nanolayer fabrication on Ge for spintronic applications. During Mn (thin-film)/Ge reaction, Mn5Ge3 is the first phase to form, being thermally stable up to 310 °C and exhibiting ferromagnetic properties up to TC ~ 300 K.

Silicide growth via reaction between a metallic film and a Si substrate has been well documented. In general, atomic transport kinetic during the growth of silicides is considered to be the same as during equilibrium diffusion, despite the reaction and its possible injection of point-defects in the two phases on each side of the interface. To date, the main studies aiming to investigate atomic transport during silicide growth used immobile markers in order to determine which element diffuses the fastest during growth and in which proportion. The quantitative measurements of effective diffusion coefficients during growth was also performed using Deal-and-Groove-type of models, however, these effective coefficients are in general not in agreement with the interdiffusion coefficients calculated using the equilibrium diffusion coefficients measured during diffusion experiments. In general, atomic transport kinetic measurements during growth and without growth are performed using different types of samples for experimental reasons. In this paper, we discuss the possible use of ultrahigh vacuum in situ Auger electron spectroscopy in order to measure the effective diffusion coefficient during growth, as well as the equilibrium self-diffusion coefficients, in the same samples, in the same experimental conditions. The first results on the Pd-Si system show that atomic transport during Pd2Si growth is several orders of magnitude faster than at equilibrium without interfacial reaction.

Atomic redistribution of W and Fe in Si were studied using secondary ion mass spectrometry and transmission electron microscopy. W diffusion experiments performed during isothermal annealing and during Si oxidation show that W atoms should use at least two different diffusion mechanisms. Experimental diffusion profiles can be well simulated by considering the simultaneous use of three different W diffusion mechanisms: the dissociative and the kick-out mechanisms, as well as an original mechanism based on the formation of a W-Si self-interstitial pair located on the interstitial Si sub-lattice. Fe redistribution was studied during the oxidation of a Fe-contaminated Si wafer. Fe is shown to be first pushed-out in Si by the mobile SiO2/Si interface, and thus to form Fe silicides precipitates at this interface. The silicide precipitates, which can exhibit a core-shell structure, appear to move with the SiO2/Si interface thanks to an oxidation/dissolution mechanism in the SiO2 and a nucleation/growth mechanism in the Si matrix. Furthermore, the rate difference between Si and Fe silicide precipitate oxidation leads to the formation of Si pyramidal defects at the SiO2/Si interface.

In this work a novel process allowing for the production of nanoporous Ge thin films is presented. This process uses the combination of two techniques: Ge sputtering on SiO2 and dopant ion implantation. The process entails four successive steps: (i) Ge sputtering on SiO2, (ii) implantation preannealing, (iii) high-dose dopant implantation, and (iv) implantation postannealing. Scanning electron microscopy and transmission electron microscopy were used to characterize the morphology of the Ge film at different process steps under different postannealing conditions. For the same postannealing conditions, the Ge film topology was shown to be similar for different implantation doses and different dopants. However, the film topology can be controlled by adjusting the postannealing conditions.

International audience; Magnetocaloric effects are of great interest for magnetic refrigeration as well as thermomagnetic energy production. Materials based on MnCoGe have been shown to be promising candidates in this respect. In this study, structural, electronic, and magnetic properties of MnCoGe alloys with several compositions (stoichiometric and Mn-depleted) have been investigated using first-principles calculations based on density functional theory. Their stability in the orthorhombic and hexagonal structure has been determined for different spin configurations. In all materials, the ferromagnetic orthorhombic phase is most stable; however, variation of the composition can lead to a decrease of the energy difference between the equilibrium orthorhombic and hexagonal structure. The magnetic moment is primarily found on the Mn atoms leading to a decrease of the total magnetic moment with decreasing amount of Mn. Using the Boltzmann transport model and the electronic density of states, the spin Seebeck coefficient has been estimated. At room temperature, it is found to be highest in stoichiometric MnCoGe in the orthorhombic crystal structure.

International audience; PdGe contact fabrication on Se-doped Ge(001) is investigated. PdGe thin film resistivity is two times lower if the PdGe layer is grown by Pd reactive diffusion on Se-doped Ge, compared to PdGe layer grown in the same condition on Se-free Ge. The phase sequence and the phase growth kinetics during Pd reactive diffusion with Ge are not modified by the presence of Se atoms. However, the PdGe film texture is different with Se, and Se segregates at the PdGe/Ge interface. These results suggest that Se atoms may be used to produce efficient contacts on n-type Ge. (c) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

International audience

In microelectronics, the increase in complexity and the reduction of devices dimensions make essential the development of new characterization tools and methodologies. Indeed advanced characterization methods with very high spatial resolution are needed to analyze the redistribution at the nanoscale in devices and interconnections. The atom probe tomography has become an essential analysis to study materials at the nanometer scale. This instrument is the only analytical microscope capable to produce 3D maps of the distribution of the chemical species with an atomic resolution inside a material. This technique has benefit from several instrumental improvements during last years. In particular, the use of laser for the analysis of semiconductors and insulating materials offers new perspectives for characterization. The capability of APT to map out elements at the atomic scale with high sensitivity in devices meets the characterization requirements of semiconductor devices such as the determination of elemental distributions for each device region. In this paper, several examples will show how APT can be used to characterize and understand materials and process for advanced metallization. The possibilities and performances of APT (chemical analysis of all the elements, atomic resolution, planes determination, crystallographic information…) will be described as well as some of its limitations (sample preparation, complex evaporation, detection limit, …). The examples illustrate different aspect of metallization: dopant profiling and clustering, metallic impurities segregation on dislocation, silicide formation and alloying, high K/metal gate optimization, SiGe quantum dots, as well as analysis of transistors and nanowires.

Silicidation of Ni ultra-thin films on Si(0 0 1) substrates was investigated from room temperature to 500 °C. In situ X-ray diffraction (XRD) experiments were performed to follow the reaction evolution. Transmission electron microscopy (TEM) and atomic probe tomography (APT) analyses highlight the formation of NiSi at low temperature (200 °C). A peculiar phase sequence is evidenced for the thinnest deposited Ni film for which the NiSi phase forms from the low temperatures. Structural analyses of the formed silicides indicate that the NiSi phase grows in axiotaxy with the substrate at 200 °C whereas NiSi2 rods form at higher temperatures.

Metallic silicides have been used as contact materials on source/drain and gate in metal-oxide semiconductor (MOS) structure for 40 years. Since the 65 nm technology node, NiSi is the preferred material for contact in microelectronic due to low resistivity, low thermal budget, and low Si consumption. Ni(Pt)Si with 10 at.% Pt is currently employed in recent technologies since Pt allows to stabilize NiSi at high temperature. The presence of Pt and the very low thickness (

The redistribution of arsenic and nickel during the reaction of Ni thin films with arsenic doped Si(100) substrates is studied by a combination of transmission electron microscopy (TEM), atom-probe tomography (APT) and in situ X-ray diffraction (XRD). Ni was observed at the edges of a pseudo-hexagonal dislocation loop within As^+-implanted (001)Si wafers, after recrystallisation of preamorphised Si and deposition of 100nm Ni. After an additional heat treatment at 280^oC, the same concentration profiles were found with a maximum of ~10% Ni at the edges of the dislocation loops, suggesting Cottrell atmospheres. In situ XRD showed the formation of a transient phase forming isolated grains at the @d-Ni"2Si/Si interface. Clusters containing 10% of As are present only in the transient phase. The presence of As clusters in silicide used for contact on devices might have significant influences on devices properties.

International audience; Polycrystalline Mn 5 Ge 3 thin films were produced on SiO 2 using magnetron sputtering and reactive diffusion (RD) or non-diffusive reaction (NDR). In situ X-ray diffraction and atomic force microscopy were used to determine the layer structures, and magnetic force microscopy, superconducting quantum interference device and ferromagnetic resonance were used to determine their magnetic properties. RD-mediated layers exhibit similar magnetic properties as MBE-grown monocrystalline Mn 5 Ge 3 thin films, while NDR-mediated layers show magnetic properties similar to monocrystalline C-doped Mn 5 Ge 3 C x thin films with 0.1  x  0.2. NDR appears as a CMOS-compatible efficient method to produce good magnetic quality high-curie temperature Mn 5 Ge 3 thin films.

International audience; The Si(Ge) alloy is currently used in the Complementary Metal Oxide Semiconductor (CMOS) technology, improving device performances, decreasing power consumption, and allowing stress engineering in Sibased devices. If Si(Ge) is used in transistors' source, drain and gate, it is necessary to create ohmic contacts between the first-level metal and Si(Ge). In the current Si-based CMOS technology, ohmic contacts are created via the reaction of a thin Ni(Pt) layer with doped-Si, aiming to form a thin NiSi layer on the Si substrate. A similar process should be used on Si(Ge). In this work, the first stages of Ni reaction with Si(Ge) is investigated using high resolution transmission electron microscopy and laser-assisted atom probe tomography. The first stage of Ni/Si(Ge) reaction leads to the formation of a germanosilicide layer made of Nip(Si1-xGex)(q) nano-grains exhibiting different structures and compositions. The formation of Nip(Si1-xGex)(q) phases occurs at temperatures as low as 60 degrees C. The germano-silicide grains exhibit coherent interfaces with the Si(Ge) layer, and during their growth, a fraction of the Ge atoms initially located in Si(Ge) is pushed from the Nip(Si1-xGex)(q)/Si(Ge) interface into the Si(Ge) layer, leading to Ge accumulation at this interface. This phenomenon can cause Ge accumulation up to 100%, promoting the incorporation of Ge-pure nanometric inclusions inside the germano-silicide layer. (C) 2016 Elsevier B. V. All rights reserved.

Due to experimental issues, atomic transport kinetics in nanostructures is still rarely quantitatively investigated despite its significant importance for the design of nanostructure fabrication processes and the prediction of nanoobject structure and physical property ageing. Atomic diffusion in nanostructures is expected to be mainly mediated via atomic transport in interfaces. However, in order to fully understand atomic transport in nanostructures, it is necessary to develop experimental methods allowing for the measurement of diffusion coefficients in nanovolumes, in interfaces, and in interface intersections. To date, this type of measurement has been essentially performed in nanocrystalline materials, giving access to diffusion measurements in nanocrystals corresponding to the nanograins, in grain boundaries corresponding to the interfaces between disoriented crystals of same nature, and in triple junctions corresponding to the grain boundary intersections. This chapter presents the current methods and techniques reported in the literature that have been used for such a type of measurement. Some of the original observations concerning atomic transport in nanocrystalline materials are also presented and discussed.

International audience; Heavy doping of Ge is crucial for several advanced micro-and optoelectronic applications, but, at the same time, it still remains extremely challenging. Ge heavily n-type doped at a concentration of 1 X 10(20) cm(-3) by As ion implantation and melting laser thermal annealing (LTA) is shown here to be highly metastable. Upon post-LTA conventional thermal annealing As electrically deactivates already at 350 degrees C reaching an active concentration of similar to 4 x 10(19) cm(-3). No significant As diffusion is detected up to 450 degrees C, where the As activation decreases further to similar to 3 x 10(19) cm(-3). The reason for the observed detrimental deactivation was investigated by Atom Probe Tomography and in situ High Resolution X-Ray Diffraction measurements. In general, the thermal stability of heavily doped Ge layers needs to be carefully evaluated because, as shown here, deactivation might occur at very low temperatures, close to those required for low resistivity Ohmic contacting of n-type Ge.

International audience; The structure and the chemical composition of Pd germanides formed on Ge(100) were investigated using transmission electron microscopy (TEM), in-situ X-ray diffraction (XRD), and atom probe tomography (APT). An ultra thin Si film used as a marker was deposited on Ge(100) prior to Pd film deposition in order to identify the diffusing species during the Pd2Ge growth. The observations evidenced the formation of a thin interfacial poly-crystalline Pd2Ge layer during Pd room-temperature deposition on Ge(100). In-situ XRD thermal treatments ranging from 50 to 400 degrees C revealed that the Si marker had no influence on the sequential formation of Pd2Ge and PdGe. Ex situ APT and TEM characterizations showed that the Si marker layer was located closer to the Pd2Ge/Ge interface than to the Pd2Ge surface, after reaction. This result indicates that Ge and Pd self-diffusion are in the same order of magnitude during Pd2Ge growth. (C) 2016 Elsevier B.V. All rights reserved.

International audience; Pd-Ge reactive-diffusion in two different samples Pd/Ge(001) and Pd/PdGe/Ge(001) was studied experimentally and theoretically, in order to clearly identify the driving force controlling the first-phase selection in the sequential phase formation regime. The experimental and theoretical results both show that only the atomic transport kinetic in the phases controls the first -phase selection: the phase exhibiting the fastest atomic self-diffusion forms first, even if its formation energy is not the lowest. (C) 2016 Elsevier Ltd. All rights reserved.

International audience; The thermal stability of PdGe on Ge(100) was investigated by scanning electron microscopy, X-ray diffraction and atom probe tomography. The initial PdGe film agglomerates when heated at high temperature (>= 500 degrees C), forming spherical islands. This degradation is highly detrimental for PdGe ohmic contact fabrication in the Gebased nano-electronics technology. However, capping the Pd layer with W before Pd-Ge reaction increases the thermal stability of the PdGe film up to 600 degrees C. In addition, the PdGe texture is modified if the sample is heated during Pd deposition, increasing the thermal stability of PdGe up to 700 degrees C with the W cap. (C) 2016 Elsevier Ltd. All rights reserved.

With the development of nanotechnologies, the number of industrial processes dealing with the production of nanostructures or nanoobjects is in constant progress (microelectronics, metallurgy). Thus, knowledge of atom mobility and the understanding of atom redistribution in nanoobjects and during their fabrication have become subjects of increasing importance, since they are key parameters to control nanofabrication. Especially, todays materials can be both composed of nanoobjects as clusters or decorated defects, and contain a large number of interfaces as in nanometer-thick film stacking and buried nanowires or nanoislands. Atom redistribution in this type of materials is quite complex due to the combination of different effects, such as composition and stress, and is still not very well known due to experimental issues. For example, it has been shown that atomic transport in nanocrystalline layers can be several orders of magnitude faster than in microcrystalline layers, though the reason for this mobility increase is still under debate. Effective diffusion in nanocrystalline layers is expected to be highly dependent on interface and grain boundary (GB) diffusion, as well as triple junction diffusion. However, experimental measurements of diffusion coefficients in nanograins, nanograin boundaries, triple junctions, and interfaces, as well as investigations concerning diffusion mechanisms, and defect formation and mobility in these different diffusion paths are today still needed, in order to give a complete picture of nanodiffusion and nanosize effects upon atom transport. In this paper, we present recent studies dealing with diffusion in nanocrystalline materials using original simulations combined with usual 1D composition profile measurements, or using the particular abilities of atom probe tomography (APT) to experimentally characterize interfaces. We present techniques allowing for the simultaneous measurement of grain and GB diffusion coefficients in polycrystals, as well as the measurement of nanograin lattice diffusion and triple junction diffusion. We also show that laser-assisted APT microscopy is the ideal tool to study interface diffusion and nanodiffusion in nanostructures, since it allows the determination of 1D, 2D and 3D atomic distributions that can be analyzed using diffusion analytical solutions or numerical simulation.