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International audience; Rational characterization of most organometallic compounds is hampered by their high reactivity, in particular, toward oxygen and water. Mass spectrometry experiments require physical introduction of the sample in the ionization source. So, the main challenge is to transfer air-sensitive organometallic compounds from inert atmosphere to the ionization source. In this aim, we have developed an easy technique that allows the analysis of air-sensitive compounds using the atmospheric solid analysis probe (ASAP). This method consists of a glass capillary filled with the sample (solid or liquid) and sealed by a paraffin plug to maintain the inert sample until the ionization process. It is illustrated through the structural characterization of a new highly air-sensitive dinuclear zirconium complex supported by an original switchable stilbene platform.

Copper is the conventional, broadly applied anode current collector in lithium-ion batteries, because Li does not form intermetallic alloys with Cu at room temperature. Fast diffusion and trapping of lithium in copper were, however, suggested in the past, and the involved diffusion mechanisms are still not clarified. By using three complementary methods, we determine grain boundary and lattice diffusion of lithium in copper. We show that indiffusion into copper is possible not only from metallic lithium deposits at the surface but also from a Li+-containing electrolyte. Lattice diffusion (D0 = 3.9 × 10-9 cm2/s; Ea = 0.68 eV) and grain boundary diffusion (D0 = 1.5 × 10-11 cm2/s; Ea = 0.36 eV) are found to be 13 orders of magnitude lower than previously published. Furthermore, for practical Li-ion battery considerations, lithium trapping in copper current collectors, which relies heavily on operating temperature and morphology, is discussed. ispartof: JOURNAL OF PHYSICAL CHEMISTRY LETTERS vol:10 issue:17 pages:5206-5210 ispartof: location:United States status: published

Colloidal quantum dots (QDs) made from In-based III-V semiconductors are emerging as a printable infrared material. However, the formulation of infrared inks and the formation of electrically conductive QD coatings is hampered by a limited understanding of the surface chemistry of In-based QDs. In this work, we present a case study on the surface termination of IR active III-V QDs absorbing at 1220 nm that were synthesized by reducing a mixture of indium halides and an aminoarsine by an aminophosphine in oleylamine. We find that this recently established synthesis method yields In(As,P) QDs with minor phosphorus admixing and a surface terminated by a mixture of oleylamine and chloride. Exposing these QDs to protic surface-active compounds RXH, such as fatty acids or alkanethiols, initiates a ligand exchange reaction involving the binding of the conjugate base RX- and the desorption of 1 equiv of alkylammonium chloride. Using density functional theory simulations, we confirm that the formation of the alkylammonium chloride salt can provide the energy needed to drive such acid/base mediated ligand exchange reactions, even for weak organic acids such as alkanethiols. We conclude that the unique surface termination of In(As,P) QDs, consisting of a mixture of L-type and X-type ligands and acid/base mediated ligand exchange, can form a general model for In-based III-V QDs synthesized using indium halides and aminopnictogens.

International audience; New platforms for trinuclear complexes, 1,3,5-tris(fluoren-2-yl-R)benzene (Ph{2-FluRH}3; R = H (2a), 6-tBu (2b), 7-tBu (2c), Tet (2d) (Tet = 2,2,5,5-tetramethyl-tetrahydrobenzofluorene), were synthesized via an acid-catalyzed cyclotrimerization of the corresponding substituted 2-acetylfluorenes. Subsequent nucleophilic addition of the [Ph{2-FluR}3]3− trianions onto 6,6,-dimethylfulvene afforded the corresponding isopropylidene-bridged pro-ligands Ph{Me2C(2-FluRH)(C5H5)}3 (3a-d). Discrete trinuclear tris(dichloro-ansa-zirconocene and hafnocene), Ph[{Me2C(2-FluR)(C5H4)}MX2]3 (X = Cl 4b-d-Zr, 4c,d-Hf) were prepared by salt metathesis reactions. Some zirconium complexes were further alkylated towards the corresponding tris(dialkyls) (X = Me 5c,d-Zr; X = CH2SiMe3 6c-Zr). The structures of these metal complexes were determined by elemental analyses, and by 1D, inverse 2D heteronuclear correlation, and DOSY NMR spectroscopy, as well as by theoretical computations. Those studies revealed the existence of two isomers, of C3 and C1 symmetry respectively, originating from the mutual orientation of the three ansa-metallocene fragments. Preliminary studies on the catalytic performances of the dichloro complexes, upon activation with MAO, in ethylene and propylene homopolymerization and ethylene/1-hexene copolymerization were carried out and compared to those of the monometallic analogues under identical conditions.

Core crystalline silicon nanowires with a heavily reduced amorphous shell have been successfully synthesised using palladium as a metal catalyst. We present two approaches to reduce the oxidation of the nanowires during the thermal annealing growth. The ratios of the amorphous shell to crystalline core of the nanowires produced, from the two methods, are compared and show a remarkable drop (hence thinner oxide) compared to wires fabricated using currently available techniques. In addition, a focused ion beam was utilised to contact the oxide-reduced nanowires for transport measurements, without first removing the thin oxide shell. The oxygen-reduced core-shell silicon nanowires showed a very low electrical resistivity (4 × 10−1 Ω cm). Our novel approach presents a new alternative to the production of low cost, high yield, highly conducting silicon nanowires offering a wide range of opportunities for semiconductor based technology.

The increase in superconducting transition temperature (TC) of Sn nanostructures in comparison to bulk, was studied. Changes in the phonon density of states (PDOS) of the weakly coupled superconductor Sn were analyzed and correlated with the increase in TC measured by magnetometry. The PDOS of all nanostructured samples shows a slightly increased number of low-energy phonon modes and a strong decrease in the number of high-energy phonon modes in comparison to the bulk Sn PDOS. The phonon densities of states, which were determined previously using nuclear resonant inelastic X-ray scattering, were used to calculate the superconducting transition temperature using the Allen-Dynes-McMillan (ADMM) formalism. Both the calculated as well as the experimentally determined values of TC show an increase compared to the bulk superconducting transition temperature. The good agreement between these values indicates that phonon softening has a major influence on the superconducting transition temperature of Sn nanostructures. The influence of electron confinement effects appears to be minor in these systems.

A bio-based polyimine vitrimer containing 100% renewable carbon content has been synthesised and characterised. This vitrimer material was prepared by combining a bio-based furan dialdehyde obtained from fructose with a bio-based diamine and triamine prepared from fatty acids. Due to the dynamic nature of the imine reversible bonds, the vitrimer properties can be clearly demonstrated. The obtained films exhibit fast stress relaxation around room temperature. To the best of our knowledge, this is the first report of a fully bio-based polyimine vitrimer.

The current knowledge about composite material machining is inadequate for its optimum utilization in many applications owing to the complexity of the phenomena involved in the cutting area. The objective of this study is to investigate the cutting mechanisms during carbon/epoxy composite drilling. It has been found that fiber orientation relative to the cutting direction is a key factor affecting machining results. Orthogonal cutting has helped to understand phenomena involved in the cutting area. The most common mechanisms noted are shearing, bending, and fiber/matrix interface debonding. It has been also noticed that surface quality, temperature fields’ cartographies, and cutting forces change markedly with fiber orientation.

The morphology evolution of supported palladium nanoparticles (Pd NPs) during plasma-enhanced atomic layer deposition using palladium hexafluoroacetylacetonate (Pd(hfac)2) as precursor was investigated using in situ and ex situ X-ray fluorescence (XRF) and grazing incidence small angle X-ray scattering (GISAXS), as well as ex situ scanning electron microscopy (SEM). The initial areal density of Pd NPs increases through adding cycles of the three-step process using Pd(hfac)2, H2 plasma and trimethylaluminum (TMA) prior to the standard Pd(hfac)2 + H2 plasma process. The participation of an O2 plasma exposure as additional co-reactant before or after the H2 plasma step also plays a role in the nucleation density and particle coalescence, affecting also the shape of the deposited particles. Based on the gathered knowledge, a synthetic approach that enables precise control of the Pd nanoparticle dimensions and coverage is developed.

The lattice location of ion implanted radioactive 24Na (t1/2=14.96 h) in GaN and AlN was determined using the emission channeling technique at the ISOLDE/CERN facility. In the room temperature as-implanted state in both GaN and AlN, the majority of the sodium atoms are found on interstitial sites near the octahedral position, with a minority on cation Ga or Al substitutional sites. Following annealing at 800-900°C the interstitial fraction is reduced while the substitutional incorporation increases. Our results thus further establish the amphoteric character of Na in GaN and AlN, in analogy to the other light alkali Li, and alkaline earths Be and Mg. The site changes upon annealing are attributed to the onset of migration of interstitial Na, for which an activation energy of 2.2-3.4 eV is estimated in GaN and 2.0-3.1 eV in AlN, and its subsequent capture by cation vacancies resulting from the implan-tation. Comparison of the lattice site change behavior of Li, Be, Na and Mg shows that the onset of interstitial mi-gration correlates with the ionic radii of these elements.

To accurately identify the material characteristics in material testing, the control of the initial and boundary conditions is very important. Among these conditions, obtaining a repeatable and known loading is a sensitive point especially for tests in the dynamic and impulsional range. Several techniques are used to generate blast wave loads. This paper focuses on the use of an explosive driven shock tube (EDST). The results of a series of tests using an EDST are discussed, with regard to the pressure, the impulse, the wave planarity and the repeatability of the loading. The EDST and free air blast are used to generate blast loading on fully clamped square aluminium plates. The response from both loads is measured with a high-speed 3D digital image correlation (DIC) system and compared to each other. The DIC measurements are compared to strain gauge measurement for validation purposes. It is found that EDST allows to reach higher levels of pressure and impulse than the free air blast leading to higher deformations and strain rates. It is also observed that the EDST tests show a higher repeatability and symmetry relative to the free air blast tests.

© 2018 Author(s). The electrical contact of the source and drain regions in state-of-the-art CMOS transistors is nowadays facilitated through NiSi, which is often alloyed with Pt in order to avoid morphological agglomeration of the silicide film. However, the solid-state reaction between as-deposited Ni and the Si substrate exhibits a peculiar change for as-deposited Ni films thinner than a critical thickness of tc = 5 nm. Whereas thicker films form polycrystalline NiSi upon annealing above 450 ° C, thinner films form epitaxial NiSi2 films that exhibit a high resistance toward agglomeration. For industrial applications, it is therefore of utmost importance to assess the critical thickness with high certainty and find novel methodologies to either increase or decrease its value, depending on the aimed silicide formation. This paper investigates Ni films between 0 and 15 nm initial thickness by use of "thickness gradients," which provide semi-continuous information on silicide formation and stability as a function of as-deposited layer thickness. The alloying of these Ni layers with 10% Al, Co, Ge, Pd, or Pt renders a significant change in the phase sequence as a function of thickness and dependent on the alloying element. The addition of these ternary impurities therefore changes the critical thickness tc. The results are discussed in the framework of classical nucleation theory. ispartof: Journal of Applied Physics vol:123 issue:7 status: published

Constitutional dynamic libraries of hydrazones (a)A(b)B and acylhydrazones (a)A(c)C undergo reorganization and adaptation in response to a chemical effector (metal cations) or a physical stimulus (light). The set of hydrazones [(1)A(1)B, (1)A(2)B, (2)A(1)B, (2)A(2)B] undergoes metalloselection on addition of zinc cations which drive the amplification of Zn((1)A(2)B)2 by selection of the fittest component (1)A(2)B. The set of acylhydrazones [E-(1)A(1)C, (1)A(2)C, (2)A(1)C, (2)A(2)C] undergoes photoselection by irradiation of the system, which causes photoisomerization of E-(1)A(1)C into Z-(1)A(1)C with amplification of the latter. The set of acyl hydrazones [E-(1)A(1)C, (1)A(3)C, (2)A(1)C, (2)A(3)C] undergoes a dual adaptation via component exchange and selection in response to two orthogonal external agents: a chemical effector, metal cations, and a physical stimulus, light irradiation. Metalloselection takes place on addition of zinc cations which drive the amplification of Zn((1)A(3)C)2 by selection of the fittest constituent (1)A(3)C. Photoselection is obtained on irradiation of the acylhydrazones that leads to photoisomerization from E-(1)A(1)C to Z-(1)A(1)C configuration with amplification of the latter. These changes may be represented by square constitutional dynamic networks that display up-regulation of the pairs of agonists ((1)A(2)B, (2)A(1)B), (Z-(1)A(1)C, (2)A(2)C), ((1)A(3)C, (2)A(1)C), (Z-(1)A(1)C, (2)A(3)C) and the simultaneous down-regulation of the pairs of antagonists ((1)A(1)B, (2)A(2)B), ((1)A(2)C, (2)A(1)C), (E-(1)A(1)C, (2)A(3)C), ((1)A(3)C, (2)A(1)C). The orthogonal dual adaptation undergone by the set of acylhydrazones amounts to a network switching process.

In this study, we focus on phase formation in intermixed Ni-Ge thin films as they represent a simplified model of the small intermixed interface layer that is believed to form upon deposition of Ni on Ge and where initial phase formation happens. A combinatorial sputter deposition technique was used to co-deposit a range of intermixed Ni-Ge thin films with Ge concentrations varying between 0 and 50 at.%Ge in a single deposition on both Ge (100) and inert SiO2 substrates. In situ X-ray diffraction and transmission electron microscopy where used to study phase formation. In almost the entire composition range under investigation, crystalline phases where found to be present in the as-deposited films. Between 36 and 48 at.%Ge, high-temperature hexagonal nickel germanides were found to occur metastabily below 300 °C, both on SiO 2 and Ge (100) substrates. For Ge concentrations in the range between 36 and 42 at.%, this hexagonal germanide phase was even found to be present at room temperature in the as-deposited films. The results obtained in this work could provide more insight in the phase sequence of a pure Ni film on Ge. © 2013 Elsevier B.V. All rights reserved. publisher: Elsevier articletitle: Phase formation in intermixed Ni–Ge thin films: Influence of Ge content and low-temperature nucleation of hexagonal nickel germanides journaltitle: Microelectronic Engineering articlelink: http://dx.doi.org/10.1016/j.mee.2013.09.004 content_type: article copyright: Copyright © 2013 Elsevier B.V. All rights reserved. ispartof: MICROELECTRONIC ENGINEERING vol:120 pages:168-173 status: published

The evolution of carbon/epoxy composites use in aeronautics requires a better comprehension of the machining conditions influence on these materials. This study aim is to establish, based on the experimentation, the relationship between machining conditions and the behavior of drilled 2D and 3D carbon/epoxy composites. Two drill geometries, seam introducing and a range of cutting speed and feed have been tested. The effect of each parameter has been assessed in terms of thrust force, moment (recorded during machining) and defects (performed by macroscopic analyses and quantified using delamination factor Fd). Experimental results have shown significant influences of feed and drill geometry on delamination reduction. The use of a spur drill and a low feed generates minor defects and produces the best results. Furthermore, stitching helps reduce damage inside the hole.

The main purpose of composite materials drilling is the need to put together different parts of a structure, in aeronautics for example. The objective of this study is to experimentally analyze the influence of drilling on a carbon/epoxy composite. Three geometries of drill, a range of cutting speed and feed have been tested. Thrust forces and moments have been recorded during machining and macroscopic analyses have been conducted to examine outside and inside surfaces of the holes. Damages have been also quantified using delamination factor Fd. Experimental results have shown significant influences of feed and drill geometry on delamination and the best results have been obtained using a spur drill.

We present a fundamental study of the monolayer adsorption of sulfur on Ge(100) surfaces from aqueous (NH4)2S solution. This treatment shows promising perspectives for the passivation of high-mobility semiconductor surfaces and is therefore presently of great technological importance. The adsorption mechanisms as well as the adsorption geometry are thoroughly investigated at the atomic scale, by both experiment and theory, applying X-ray absorption spectroscopy and molecular dynamics simulations. Our findings indicate that sulfidation in solution results in the formation of Ge–S–Ge bridges along the [110] direction, with no indication for −SH surface groups. A S–Ge bond length of 2.25 ± 0.05 A was deduced, which is affected by the chemical environment of the sulfur atoms, i.e., by residual surface oxides. Our study provides novel insights into the surface termination and atomic structure of (NH4)2S-treated Ge(100) surfaces and discusses possible differences from in situ sulfur adsorption methods such as H...

The dynamic behaviour of structures under blast wave loading is increasingly studied due to the rising risks of intentional and accidental explosions and the development of new protective technologies and methods. To ensure the efficiency of these protective measures, the identification of the material behaviour under blast loading is of utmost importance. This paper investigates the feasibility of the identification of the strain rate hardening of aluminium using an inverse method and blast loads. The results of a series of tests on aluminium plates loaded by means of an Explosive Driven Shock Tube are reported. A numerical study is performed to develop a model that is both in concordance with the experimental measurements and suitable for loop implementation. The 3D high-speed full-field measurements and finite element simulations are used to accurately assess the dynamic response of the plates. The identification is based on the Levenberg-Marquardt formulation for damped least-squares solution. The approach is virtually validated and its sensitivity to noise is studied using virtual measurements from finite element calculations. Then, experimental data are used for the identification. The results obtained are within the range of expected values based on literature.

The effective passivation of germanium surfaces and interfaces has been claimed to be the key to a substantial progress in developing Ge-based microelectronic devices. This paper compares the currently most promising passivation routes, i.e. oxidation and sulfidation, focusing on the underlying atomic scale processes and highlighting similarities and discrepancies between both approaches. The effect of oxidation and sulfidation on electrically active defects is addressed, and the chemical and structural properties of the passivated surfaces are described in detail.

A diffuse reflectance infrared Fourier‐transform (DRIFT) study has been conducted at 373 K and 1 bar on an industrial Cr/Ti/SiO2 Phillips‐type catalyst modified with, and without, triethylaluminium (TEAl) as co‐catalyst. The reaction rate of the polymerization of ethylene, as monitored by the increase in the methylene stretching band of the growing polyethylene (PE), has been investigated as a function of the titanium content. After an initial period of mixed kinetics, with the reaction rate significantly higher for the TEAl‐modified catalysts compared with the non‐modified catalysts, the polymerization proceeded as a pseudo‐zero‐order reaction with a reaction rate that increased as a function of titanium loading. Furthermore, it was found that the higher Ti loading caused the appearance of more acidic hydroxyl groups and modified the Cr sites by making them more Lewis acidic, ultimately shortening the induction time and increasing the initial polymerization rate.

A silicon nitride ring resonator with implanted ytterbium ions offers a means for greatly enhanced ion–light interactions in an integrated optics platform. Rare-earth ions in solids are of particular interest for quantum information storage and processing because of the long coherence times of the 4f states1. In the past few years, substantial progress has been made by using ensembles of ions2,3,4,5,6 and single ions7,8,9,10. However, the weak optical transitions within the 4f manifold pose a great challenge to the optical interaction with a single rare-earth ion on a single-photon level. Here, we demonstrate a ninefold enhanced ion–light interaction (Purcell effect11) in an integrated-optics-based, fibre-coupled silicon nitride (Si3N4) ring resonator with implanted ytterbium ions (Yb3+). We unveil the one-, two- and three-dimensional contributions to the Purcell factor as well as the temperature-dependent decoherence and depolarization of the ions. The results indicate that this cavity quantum electrodynamics (QED) system has the potential of interfacing single rare-earth ions with single photons on a chip.

We have used real-time Rutherford backscattering spectrometry to determine the dominant diffusing species during the formation of nickel germanide and palladium germanide; two of the most promising candidates for use as ohmic contacts were germanium to replace silicon in devices. In the Ni/Ge system Ni 5 Ge 3 is the first phase to form, followed by NiGe. The results show that during Ni 5 Ge 3 formation Ni is essentially the sole diffusing species and is responsible for almost all the growth. During the 2nd-phase formation both Ni and Ge diffuse, with the Ge diffusion prominent during the very early stages, while the later stage of growth is dominated by Ni diffusion. During the formation of Pd 2 Ge and PdGe phases the metal (i.e. palladium) is once again the dominant diffusing species. The relative contribution of germanium diffusion to the growth is, however, more prominent in the Pd/Ge system, with significant amounts of Ge diffusion being observed during formation of both phases.

Germanium is considered to be a potential semiconductor to replace silicon in future high-performance microelectronic devices. Yet, when compared to Si, very little is known about the surface chemistry of Ge surfaces. In this article, we report on the oxygen adsorption on Ge(100)-(2 × 1) surfaces and the related changes in the density of surface states. In particular, the adsorption geometry is examined both in reciprocal- and real-space using reflection high-energy electron diffraction and scanning tunneling microscopy, respectively. Our findings reveal that the insertion of oxygen atoms into the Ge backbonds is not favored under the investigated reaction conditions, i.e., at a moderate O2 exposure. The O2-exposed surface exhibits a local (1 × 1) surface reconstruction, which implies that dimer bonds are destroyed upon oxygen adsorption. Surface states related to Ge dangling surface bonds present on the clean Ge(100) surface are found to be passivated. In addition, a high density of expelled substrate at...

The last decennia, a lot of effort has been made to introduce new channel materials in a Si process flow. High mobility materials such as Ge need a good gate stack passivation in order to ensure optimal MOSFET operation. Several routes for passivating the Ge gate stack have been explored in the last years. We present here the S-passivation of the Ge gate stack: (NH4)2S is used to create a S-terminated Ge surface. In this paper the S-treatment is discussed. The S-terminated Ge surface is not chemically passive but can still react with air. After gate oxide deposition, the Ge-S bonds are preserved and an adequate passivation is found for pMOS operation.

We have demonstrated the formation of Ni(Ge 1− y Sn y ) layers on Ge 1− x Sn x layers by using solid-phase reaction for samples with Sn contents ranging from 2.0% to 6.5%. We have also investigated solid-phase reaction products in Ni/Ge 1− x Sn x /Ge samples after annealing and the crystalline properties of nickel–tin–germanide layer/Ge 1− x Sn x contact structures. After annealing at temperatures ranging from 350 to 550 °C, the formation of polycrystalline Ni(Ge 1− y Sn y ) layers has been observed on epitaxial Ge 1− x Sn x layers with Sn contents ranging from 2.0% to 6.5%. We also observed anisotropic crystal deformation of NiGe with the incorporation of Sn atoms into substitutional sites in NiGe. In the case of the Ni/Ge 1− x Sn x /Ge sample with a Sn content of 3.6%, the formation of an epitaxial Ni 2 (Ge 1− z Sn z ) layer on the Ge 1− x Sn x layer was found. The formation of β-Sn crystallites was observed after annealing at above 450 °C in samples with a high Sn content of 6.5%. This β-Sn formation is due to the precipitation of Sn atoms. In all samples annealed at 350 °C, the morphology of Ni–Ge–Sn layers is smooth and uniform. However, the surface roughness and interface roughness increase for an annealing temperature of 550 °C. In particular, in the sample with a Sn content of 6.5%, the temperature at which agglomeration noticeably occurs is as low as 450 °C.

In order to outperform current uniaxial compressively strained Silicon channel pMOSFET technology (with embedded SiGe source/drain), switching to strained Ge channel is mandatory. GeSn materials, having larger lattice parameter than Ge, are proposed in this article as embedded source/drain stressors for Ge channels. Our simulation results indicate that a minimum of 5% Sn is required in the GeSn source/drain to build a competitive strained Ge pMOSFETs with respect to strained Si channels. Therefore the compatibility of GeSn (with 2-8% Sn) materials with source/drain engineering processes (B implantation and activation and NiGeSn formation) has been studied. A low thermal budget has been determined for those processes on GeSn alloys: temperatures must be lower than 600^oC for B activation and lower than 450^oC for NiGeSn formation.

By use of a glasselectrode or a sodium ISE the authors try to determine secondary effects influencing the emf values when studying the dissociation of α-OH-isobutyric acid at I=1 and 25°C.

The optical and resistivity properties of Pd/Co films are investigated and related to the interaction of palladium and the underlying cobalt (Co) clusters layer when exposed to hydrogen. Co is used because it is known to absorb hydrogen only on its surface. Co clusters with mean size of 1.8 nm in the gas phase were deposited on sapphire substrates at room temperature (RT), 300 °C, and 500 °C, respectively, and capped by a continuous Pd film. Light transmission and reflection in the visible range were measured during hydrogen exposure at different pressures in consecutive cycles. An unusual change in the transmittance and the resistance during the first hydrogenation cycle of a sample suggests that a reduction of the surface oxide on the Co clusters layer occurs at room temperature. The reduction of the native oxide on Co thin films or bulk does not happen without the Pd capping when exposed to hydrogen under similar conditions.

The phase formation in the ternary Ni/Yb/Si system was studied for Ni–Yb alloy and interlayer structures on Si(100) substrates using in situ x-ray diffraction measurements. Yb was treated as an alloying element in the Ni–Si system with Yb concentrations varying between 0 and 40 at. % of the Ni concentration. Independent of the initial structure of the sample, a Ni–Si or Ni–Yb compound was detected first which suggests that Ni is the dominant diffusing species during the solid state reactions. No pure Yb silicides were identified but a ternary phase (YbNi2Si2) formed in all samples after the Si atoms became mobile. Information about the distribution of the phases throughout the thin silicide film was obtained using ex situ Rutherford backscattering analysis. Independent of the Yb concentration, the NiSi phase formed at the substrate interface. As a result, the immobile Yb atoms shifted toward the sample surface and no detectable amount of Yb atoms was left at the Ni-silicide/Si interface after annealing.

Deep-level transient spectroscopy (DLTS) measurements were used to characterize the electrical properties of MOCVD grown, europium- (Eu) and xenon- (Xe) implanted GaN films on sapphire substrates. Implantation energy was 80 keV with a fluence of 110 14 cm 2 along a channeled crystallographic direction. Defect levels were observed at EC 0.19 eV for both Eu- and Xe-implantation which were predicted to be a rare-earth related donor level by theoretical calculations. Other defect levels are observed with energy levels located at 0.22, 0.68, 0.49, 0.60, 0.77 eV and 0.48, 0.64, 0.45, 0.72 eV below the conduction band for Eu and Xe implantation, respectively. Some of these levels have similar defect signatures and can be related to other implantation related defects introduced in erbium, praseodymium and helium implantations.

Using complementary surface analysis techniques, we have studied the chemical and structural properties of the S/Ge(100) passivation layer formed upon sulfidation in an aqueous (NH4)2S solution. Our experiments have revealed that only S-Ge bonds are formed upon the adsorption of S and that the surface is essentially free of other S-containing species (i.e. Sn or SOx). The passivation treatment was found to reduce, but not to fully inhibit Ge-O bonds on the surface. Moreover, we have shown that the top-layer of the passivated surface shows a high degree of disorder even though it is associated with a spotty (1x1) RHEED pattern. Based on our experimental findings, we conclude that the passivation layer can be best described as a thin amorphous GeSxOy film atop a partially ordered interfacial layer, a surface model that has been proposed previously in literature.

Applying both template and Si cap technology, we achieved the epitaxial growth of CoSi 2 directly on Si(1 0 0) substrate by rapid thermal annealing (RTA). The crystal quality of CoSi 2 film is found to be significantly dependent on the Si cap thickness. In our work, a good-quality CoSi 2 film with a minimum of χ min ~11.6% and 3.3 Ω/square was obtained as a 15 nm Co with a subsequent 15 nm Si cap layer is deposited on an oxide-mediated CoSi 2 template and followed by an anneal at 1050 °C under N 2 protection; whereas too thin or thick Si cap layer will deteriorate the crystalline quality of CoSi 2 . These experimental results are discussed in combination with the simulation of Rutherford backscattering spectroscopy and X-ray reflectivity.

Two series of supported Pd catalysts were synthesized on new mesoporous–macroporous supports (ZrO 2 , TiO 2 ) labelled M (Zr and Ti). The deposition of palladium was carried out by wet impregnation on the calcined TiO 2 and ZrO 2 supports at 400 °C (Pd/Zr 4 , Pd/Ti 4 ) and 600 °C (Pd/Zr 6 , Pd/Ti 6 ) and followed by a calcination at 400 °C for 4 h. The pre-reduced Pd/M X catalysts were investigated for the chlorobenzene total oxidation and their catalytic properties where compared to those of a reference catalyst Pd/Ti-Ref (TiO 2 from Huntsman Tioxide recalcined at 500 °C) and of a palladium supported on the fresh mesoporous–macroporous TiO 2 (Pd/Ti). Based on the activity determined by T 50 , the Pd/Ti and Pd/Ti 4 catalysts have been found to be more active than the reference one. Moreover activity decreased owing to the sequence: Pd/Ti X ≫ Pd/Zr X and in each series when the temperature of calcination of the support was raised. The overall results clearly showed that the activity was dependant on the nature of the support. The better activity of Pd/Ti X compared to Pd/Zr X was likely due to a better reducibility of the TiO 2 support (Ti 4+ into Ti 3+ ) leading to an enhancement of the oxygen mobility. Production of polychlorinated benzenes PhCl x ( x = 2–6) and of Cl 2 was also observed. Nevertheless at 500 °C the selectivity in HCl was higher than 90% for the best catalysts.

Composite materials are increasingly used for structural parts in the aeronautic industries. Carbon Fiber-Reinforced Plastics (CFRP) are often used in combination with metallic materials, mostly aluminium alloys. This raises new problems in aircraft assembly. Delamination is one of these problems. In this study, CFRP/Al-Li stacks is used as experimental material for investigation effect of interaction of cutting parameters (cutting speed and feed rate) and tool geometry on delamination and thrust forces in drilling operation. A plan of experiments, based on Taguchi design method, was employed to investigate the influence of tool geometry and in particular the point angle and cutting parameters on delamination and axial effort. The experimental results demonstrate that the feed rate is the major parameter and the importance of tool point angle in delamination and thrust forces in the stacks were shown.

With the implementation of low-energy time-of-flight Elastic Recoil Detection Analysis (ERDA), routine analysis of thin films with high depth resolution becomes possible. The optimization of the measurement conditions is a key issue for an accurate sample characterization and is normally a compromise among depth resolution, mass resolution and sensitivity, for a given sample. In this work, we focus on the depth resolution optimization, presenting an extensive study of two different materials, SiO 2 and TiN, representative of light and medium mass targets. The film thickness varies between 10 and 50 nm. The samples were measured with different beams ( 35 Cl, 63 Cu, 79 Br and 127 I), energies (from 2 to 16 MeV) and incident angles. The experimental results are supported and generalized by simulations run with the Monte Carlo code MCERD. The different contributions of the system resolution, straggling and multiple scattering are evaluated and discussed. The best surface resolution is obtained in the low-energy limit. On the other hand, at low-energy the resolution deteriorates rapidly and better results for thicker films are obtained with higher incident energies. The loss of resolution with increasing depth is dominated by multiple scattering and becomes more relevant for heavy ions and heavy target atoms. In order to maintain a good depth resolution throughout the film, reducing the incident angle is more efficient than acting on the beam energy.

The synthesis of ordered mesoporous carbon materials, which have been named CMI-8, using the hexagonally ordered mesoporous silica CMI-1 as an exotemplate is reported. The morphology of these new mesoporous carbon materials is exactly the same as the CMI-1 template. The hexagonal pore structure replication was confirmed by XRD and TEM. From a textural point of view, the carbon replica shows a type IV isotherm and a narrow pore size distribution centred at 2.2 nm. A high surface area and total pore volume, of 1653 and 0.86 cm3/g, respectively, were obtained. The advantage of using mesoporous silica CMI-1 as a template is its variable but uniform morphologies, from sphere, gyroid, toroid to ropes.

0.5 wt% palladium supported on exchanged BEA and FAU zeolites were prepared, characterized and tested in the total oxidation of volatile organic compounds (VOCs). The BEA and FAU zeolites were exchanged with different cations to study the influence of alkali metal cations (Na+, Cs+) and H+ in Pd-based catalysts on propene and toluene total oxidation. The exchange with different cations (Na+, Cs+) and H+ led to a decrease of the surface area and the micropore volume. All Pd/BEA and Pd/FAU zeolites were found to be powerful catalysts for the total oxidation of VOCs. They were active at low temperature and totally selective for CO2 and H2O. However, their activity depends significantly on the type of zeolite and on the nature of the charge-compensating cation. The activity order for propene and toluene oxidation on FAU catalysts, Pd/CsFAU > Pd/NaFAU > Pd/HFAU, is the reverse of the activity order on BEA catalysts: Pd/HBEA > Pd/NaBEA > Pd/CsBEA. The catalytic activities can be rationalized in terms of the influence of the electronegativity of the charge-compensating cation on the Pd particles, the Pd dispersion, the PdO reducibility and the adsorption energies for VOCs.

The influence of Ni thickness on the formation of Nickel suicides was systematically investigated between 0 and 15nm. Annealing thickness gradients distinguishes Alms that agglomerate (>5nm) and films that are morphologically stable (

The use of forward scattered heavy incident ions in combination with a time-of-flight-energy telescope provides a powerful tool for the analysis of very thin (5–30 nm) films. This is because of greater stopping powers and better detector energy resolution for heavier ions than in conventional He-RBS. Because of the forward scattering angle, the sensitivity is greatly enhanced, thus reducing the ion beam induced desorption during the analysis of very thin films. The drawback of forward scattering angle is the limited mass separation for target elements. We demonstrate the performance of the technique with the analysis of 25 nm thick NiSi films and atomic layer deposited 6 nm thick HfxSiyOz films on silicon using 3–8 MeV 16O ions as projectiles. In these measurements, a depth resolution of 2 nm was obtained at the surface, while deeper in the film the resolution was limited by multiple scattering. A full composition with detailed impurity analysis can be obtained by combining time-of-flight forward-scattering spectrometry (TOF-FS) and low energy TOF–ERDA measurements.

The formation of iron silicide and the reaction in interface between Fe and Si(1 0 0) were investigated by conversion electron Mossbauer spectroscopy. Depending on the thickness of the iron film (3–20 ML), different phases were observed. The reaction rate between Fe and Si was also thickness dependent. Depending on the Fe thickness and on the annealing temperature, stable (e-FeSi, β-FeSi 2 ) and metastable (disordered, c-FeSi) phases were formed. At 3 ML iron thickness an amorphous phase with hyperfine interaction parameters characteristic to that of amorphous iron silicide phase with 50 at.% Si content appeared. The parameter values of this phase changed significantly around 673 K indicating the transformation of the structure close to that of e-FeSi. At 8 and 20 ML Fe thicknesses magnetic split spectra with distribution were detected. After annealing, metastable c-FeSi, stable e-FeSi and at higher temperature stable β-FeSi 2 phases were formed.

Deep level transient spectroscopy (DLTS) and transmission electron microscopy (TEM) are used to study europium implanted gallium nitride layers. The implantation was realised at room temperature in the random and channeled geometries. From DLTS, we determine intrinsic defects with associated levels located in the band gap (below the conduction band). Besides, we point out a new electron trap named Eu2. Its associated level is located at about Ec –0.36 eV and the defect is probably related to the europium rare-earth ion. TEM investigation shows a difference in structure caused by changing the geometry of implantation. The random implanted sample contains numerous planar defects. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Erbium photoluminescence in GaN:Er was studied with above-band-gap excitation, provided by a He–Cd (λ=325nm) laser and below-band-gap excitation by a tunable Ti–Sa laser. The spectra obtained with these two lasers exhibit different spectral shapes. When both lasers are used at the same time, we observe that the Er3+ photoluminescence induced by each of the lasers is partly quenched by the illumination of the other laser. In this experiment, one of the lasers is modulated and a lock-in amplifier is used to filter the corresponding photoluminescence signal. The spectra recorded this way are found to be linear combinations of spectra obtained with each of the lasers used separately. This effect is explained by the presence of defects mediating the excitation towards the Er3+ ions. These defects act as electron traps, which can be populated by one specific laser excitation and are photo-ionized by the other laser leading to a large quenching of Er3+ emission.

Low-energy ion deposition and molecular beam epitaxy were used to systematically study the influence of the deposition energy on the growth of Co on Si(1 1 1). Co ions with a well-defined energy between 0.1 and 155 eV were deposited onto a 7 × 7 reconstructed Si surface, using sub- as well as supramonolayer coverage. For submonolayer coverage (0.3 ML), the initial periodicity degrades gradually with increasing ion energy: while for low energies (∼10 eV), 7 × 7 features remain clearly visible, these features disappear completely for higher deposition energies. In the supramonolayer (2 ML) region, we observe an increase in island density with increasing ion energy, which can be explained by the increasing amount of adatom–vacancy pairs and island breakup. Additionally, hyperthermal deposition yields a lower surface roughness compared to thermal deposition, with an optimal energy window for growing smooth films at ∼25 eV. This optimum can be attributed to enhanced layer-by-layer growth due to the extra energy provided by the incoming ion.

Thin films of e-FeSi were grown by deposition of Fe on a Si〈111〉 substrate under ultrahigh vacuum conditions, followed by in situ annealing at 450 °C. These e-FeSi films were subjected to irradiation from a pulsed excimer laser in the energy density range 0.30–0.90 J/cm2, in order to study the phase formation and crystallization processes of metastable [CsCl]Fe1−xSi phases. The samples were analyzed by Rutherford backscattering and channeling spectrometry and by cross-sectional transmission electron microscopy. Considerable diffusion of silicon into the silicide film was found to occur during the pulsed laser annealing, resulting in a film with nonstochiometric composition. In contrast to solid phase reaction, epitaxial ordering in the iron silicide film is observed during pulsed laser annealing when the film’s composition approaches that of FeSi2. Analysis by cross-sectional transmission electron microscopy confirmed that the phase which exhibits epitaxial ordering corresponds to the metastable [CsCl]Fe1...

This paper reviews the current knowledge on rare earths (REs) implanted into GaN with a special focus on their lattice location and on the optical activation by means of thermal annealing. While emission channeling experiments have given information on the lattice location of rare earths following low-dose (≈10 13 cm −2 ) implantation, both in the as-implanted state and after annealing up to 900 °C, the lattice location of higher-dose implants (10 14 –10 15 cm −2 ) and their defect annealing behaviour were studied using the Rutherford backscattering/channeling (RBS/C) method. The available channeling and luminescence results suggest that the optical activation of implanted REs in GaN is related to their incorporation in substitutional Ga sites combined with the effective removal of the implantation damage.

We have used electrical measurements Deep level transient spectroscopy (DLTS) complemented by high-resolution X-ray diffraction (HRXRD) and Rutherford backscattering spectroscopy (RBS) measurements for assessment of the defects introduced in p-Si1-xGex during 160keV erbium ion implantation. From deep-level transient spectroscopy, it was observed that two prominent defects with discrete energy levels above the valence band, were introduced during Er ion implantation. The observed defects have similar signatures as those introduced during alpha-particle irradiation and electron beam metal deposition, indicating that these defects are more likely not related to Er but only to implantation induced damage such as primary defects. The generated defects expand the Si1-xGex lattice in the implanted region, which results in the presence of the tail in the high-resolution X-ray diffraction spectra. After rapid thermal annealing (RTA) at 850degreesC for 30 s in nitrogen ambient, a reduction in defect density as well as a relaxation of the Si1-xGex lattice is observed for all x values. A dominant Er-related sharp emission in the 1.541 mum region was observed at room temperature and neither the intensity of the Er emission nor the emission peak position were influenced by the Ge content or the strain relaxation in the epilayers.

Photoluminescence (PL), photoluminescence excitation (PLE) spectra and luminescence decay of the Er 3 + 4 I 1 3 / 2 → 4 I 1 5 / 2 transition are investigated at 7 K in Er-implanted GaN samples. Under below-gap excitation,PL and PLE spectra reveal the existence of two types of Er centers. One type of Er center which can only be excited by resonant intra 4f shell transition is predominant while other Er centers are clearly excited via local defects. Evolution of Er luminescence as a function of implantation dose and implantation geometry is presented for both types of Er centers. Luminescence dynamics study shows that the 4 I 1 3 / 2 manifold has a shorter lifetime (τ ∼ 1 ms) when Er ions are part of Er-defect complexes than when Er ions are isolated from any defect (r = 3.8 ms). This result indicates the existence of non-radiative energy transfers in Er-defect complexes from Er ions towards defects or impurities. Er decay in Er-defect complexes is then successfully compared with classical energy transfer models.

The lattice site location of excited states of 149 Eu was studied by means of the emission channeling technique. The 60 keV implantation of 149 Tb into a GaN thin film was performed at room temperature up to a dose of 2.0×1013 cm−2. This radioactive isotope eventually decays into short-lived excited states of 149 Eu . The conversion electrons emitted in the subsequent decay to the 149 Eu ground state were detected with a position sensitive detector. We measured their angular distributions around the [0 0 0 1], [ 1 1 0 2 ], [ 1 1 0 1 ] and [ 2 1 1 3 ] axes in the as-implanted state and after 600 and 900 °C vacuum annealing. Already in the as-implanted state around 65% of 149∗ Eu atoms were found on substitutional Ga sites. The root mean square (rms) displacements from the substitutional sites in the as-implanted state were found to be around 0.13–0.16 A. Annealing up to 600 °C increased the substitutional fraction by a few percent and slightly reduced the rms displacements, most likely due to the removal of crystal defects in the vicinity of the Eu atoms, resulting in a better incorporation into substitutional sites.

The physical and electrical properties of an Ir/SiO2/Si stack were evaluated for advanced gate electrode application. The thermal stability of the stack was studied on MOS capacitors annealed at temperatures between 500 and 1000 °C in N2 ambient for 30 s followed by forming gas anneal (FGA) at 420 °C for 20 min. The work function of iridium, found to be 4.9 eV, is stable up to 900 °C, making it a good candidate as PMOS electrode. In addition, no evidence was found for any chemical reaction at the interface between Ir and SiO2.

Monocrystalline Si(1 1 1) targets are implanted (at room temperature) with antimony ions at 120 keV energy to 5 � /10 14 or 5 � / 10 15 Sbcm � 2 dose. The samples are heat treated by means of rapid thermal processing (RTP) at 1000 8C during 60 s, under nitrogen atmosphere. In this work, we report the measured evolution of the silicon surface damage and the radiation damage recovery in relation to antimony dose and RTP processing. We also study the behavior of antimony dopant into Si(1 1 1) specimens. The investigation is carried out by HeRutherford backscattering spectrometry (RBS; operating at 1.57 MeV energy in both random and channeling modes), X-ray diffraction (XRD) and atomic force microscopy (AFM) techniques. It is shown that a good surface damage recovery is obtained for all the annealed samples. However, after RTP, a significant loss of antimony has occurred for the specimens which are implanted with 5 � /10 15 Sbcm � 2 dose. This suggests an antimony out-diffusion. Finally, a good morphological characterization of the specimens is provided by AFM. # 2003 Elsevier B.V. All rights reserved.