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In conventional atomic layer deposition (ALD), precursors are exposed sequentially to a substrate through short pulses while kept physically separated by intermediate purge steps. Spatial ALD (SALD) is a variation of ALD in which precursors are continuously supplied in different locations and kept apart by an inert gas region or zone. Film growth is achieved by exposing the substrate to the locations containing the different precursors. Because the purge step is eliminated, the process becomes faster, being indeed compatible with fast-throughput techniques such as roll-to-roll (R2R), and much more versatile and easier and cheap to scale up. In addition, one of the main assets of SALD is that it can be performed at ambient pressure and even in the open air (i.e., without using any deposition chamber at all), while not compromising the deposition rate. In the present chapter, the fundamentals of SALD and its historical development are presented. Then, a succinct description of the different engineering approaches to SALD developed to date is provided. This is followed by the description of the particular fluid dynamics aspects and the engineering challenges associated with SALD. Finally, some of the applications in which the unique assets of SALD can be exploited are described.

With the downscaling of feature dimensions, copper interconnects exhibit properties differing from bulk or film material. Resistivity increases and limits electrical performances, and reliability of interconnects becomes a more important challenge for each new technological node. In this study, we present an approach of copper grain growth control inside narrow wires by adding a step between the copper electro-chemical deposition (ECD) and the chemical-mechanical polishing (CMP). This step corresponds to a partial CMP step (pre-CMP) and is applied after ECD and before anneal in order to modify the copper overburden thickness. Depending on the targeted thickness, copper grain growth occurs during anneal with different efficiencies. Crystallization and grain growth behaviour inside wires is investigated with focused ions beam (FIB). We present here our methodology for sample preparation and characterization. Results are focused on electrical variations and on morphological aspects of copper crystallization and grain growth inside lines observed with various overburden thicknesses.

This work reports on the crystallization of α - Si 3 N 4 , β - Si 3 N 4 , and silicon in plasma enhanced chemical vapour deposition silicon nitride films grown with SiH 4 and NH 3 at 400 ∘ C and annealed at 1150 ∘ C . Nanometric multilayer structures, composed of alternating layers of silicon nitride and silicon-rich nitride, were used as the starting material. The final product is a thin-film Si – Si 3 N 4 nanocomposite. The formation of this composite is verified using glancing incidence X-ray diffraction, transmission electron microscopy and Fourier transform infra-red spectroscopy. Annealing investigations indicate that the multilayer structure plays a key role in the formation of this composite and for the relatively low temperature formation of α - and β - Si 3 N 4 nanocrystals.

The penetration behaviour of liquid Ga along two different types of symmetrical tilt Al bicrystals is analysed as a function of tensile load applied normal to the boundary plane by means of synchrotron radiation X-ray micro-radiography. A direct relation between the grain boundary energy and the applied load required to promote liquid metal embrittlement is evidenced. Analysis of the in situ penetration experiments allows us to establish a link between crack velocity and the stress intensity factor. The thickness of the intergranular liquid Ga film is compared to the expected crack opening which accompanies crack propagation in mode I loading conditions.

The penetration of liquid Ga along the grain boundaries of Al bicrystals is analysed by synchrotron X-ray projection microscopy. Using Kirkpatrick–Baez focussing optics, a secondary X-ray source is produced of about 90 × 90 nm2 spot size and typical divergences of a few milliradians. By positioning the sample downstream this source, the spatial resolution detector limitation is overcome and the ultimate resolution is rather given by the secondary source size. The present investigation deals with one of the very first applications of such a microscope, currently under commissioning at the ID19 beamline of the European Synchrotron Radiation Facility (ESRF, Grenoble, France). In situ observations of the Ga penetration process reveal linear propagation of the penetration front accompanied by a continuous thickening of the Ga intergranular wetting layer. By combining sub-micron spatial resolution and in situ imaging capabilities it has been possible to characterize simultaneously the presence of nanometric penetration layers and, for the first time, associated continuous relative movement of the grains of final amplitude in agreement with the value of the saturated Ga layer thickness. The measured deformation of the bicrystal is compared to the predictions of elasto-plastic crack propagation under mode I loading conditions.

La penetration des metaux liquides aux joints de grains de metaux solides en l'absence de contrainte exterieure peut, pour un certain nombre de couples specifiques, conduire a la fragilisation du solide. Nous presentons dans ce papier deux techniques d'imagerie synchrotron qui sont bien adaptees pour observer ce type de phenomene. La micro-radiographie synchrotron a ete utilisee pour caracteriser la cinetique de penetration pour le couple Al/Ga. Nous montrons que la version moderne de radiographie par absorption possede la resolution spatiale et temporelle adequate pour etudier la penetration de films sub-microniques de Ga liquide localises aux joints de grains de bicristaux d'aluminium. La micro-fluorescence synchrotron est quant a elle bien adaptee pour la detection de traces d'elements dans des systemes tres dilues. Au detriment de la resolution spatiale et temporelle, cette technique permet la detection de quantites infimes d'atomes diffusant aux joints de grains de metaux solides.

An x-ray diffuse scattering investigation of p-type porous silicon (PS) is reported. Synchrotron radiation and laboratory measurements of the x-ray diffuse scattering at small and large scattering wave-vector q values are presented. At small q values and for p−-type material, small isotropic crystallites of a few nanometers diameter are shown, whereas for p+-type material the main cylindrical crystallites are larger. At large q values the fine p+ PS structure is investigated and reveals the presence of small spherical crystallites around the main cylindrical crystallites. The elastic relaxation of silicon crystallites in the porous structure is also presented for oxidized and for as-formed samples, using reciprocal space maps. PS superlattice diffuse scattering is then observed. Finally, these results are discussed in relation to previous x-ray studies and other methods of structural observation.

High resolution X-ray diffraction is used to perform an in situ measurement of the variations of the lattice parameter of the nanometer size crystallites of porous silicon, induced by the freezing of a confined organic fluid, dodecane. Two p+ type PS layers of 60 and 70% porosity are investigated, and the variations of their lattice parameter with the temperature (in the range 150–300 K) are measured. The experimental curves are discussed in relation with the results of a previous calorimetric study of the freezing of confined dodecane. We explain the observed strains by the presence of capillary stresses, that appear in the layer due to the formation of internal liquid-vapour meniscus during the freezing process of the confined fluid.

The penetration of liquid metals into the grain boundaries of polycrystalline solid metals is a precursor process triggering liquid metal embrittlement for some specific metal couples. Synchrotron radiation X-ray microtomography is used to investigate the penetration of liquid gallium into the grain boundaries of aluminium. The large difference in absorption coefficients between Ga and Al allows micrometer thick liquid Ga films to be observed as they are wetting grain boundaries of Al. The effects of annealing are presented and discussed. This technique opens the way for in-situ measurements of the kinetics of liquid metal penetration in materials. It might also be used to visualise and analyse the three-dimensional grain structure of a metallic polycrystal.

Using high resolution x-ray diffraction, the porous silicon lattice parameter was measured in vacuum, as a function of temperature in the range 90–300 K, showing that the thermal expansion of porous silicon is larger than that of bulk silicon. We then estimate the differential thermal expansion coefficient δα of p+-type porous silicon samples of various porosity (from 60% to 80%). Between 90 and 250 K, δα is constant as a function of the temperature but increases linearly with the sample porosity. The porous silicon thermal expansion is related to the temperature variation of the silicon nanocrystallite surface stress.

The structural properties of (111) oriented p+ type Porous Silicon (PS) samples are investigated using various X-ray diffraction techniques and compared to (001) p+ type PS layer structure. High resolution X-ray diffractometry was used to record rocking curves and reciprocal space maps, giving indications about the crystalline quality of the PS samples as well as about the pore orientation. X-ray diffraction and reflectivity performed on thin PS layers allow to estimate the layer thickness, porosity and roughness of the PS/substrate interface.

The structural properties of (001)- and (111)-orientedp+-type porous silicon samples have been investigated using X-ray techniques. X-ray reflectivity applied to thin layers of both orientations allows the estimation of the layer thickness, the porosity and the interface roughness. High-resolution X-ray diffraction was used to obtain symmetrical and asymmetrical rocking curves, as well as maps of the reciprocal space. The lattice-mismatch parameter was measured and some indications about the pore shape, orientation and size were deduced. The obtained X-ray curves as well as differential scanning calorimetry data are compared to discuss the influence of the substrate orientation on the structural properties ofp+-type porous silicon material.

The phase transitions of non-polar organic fluids and of water, confined in the pores of porous silicon samples, were investigated by Differential Scanning Calorimetry (DSC). Two types of PS samples (p- and p+ type) with different pore size and morphology were used (with spherical pores with a radius of about 1.5 nm and cylindrical shape with a radius of about 4 nm respectively). The DSC results clearly show that the smaller the pores are, the larger is the decrease in the transition temperature. Moreover, a larger hysteresis between melting and freezing is observed for p+ type than for p- type samples. A critical review of the thermodynamical properties of small particles and confined fluids is presented and used to interpret and discuss our DSC results. The effects of the chemical dissolution as well as the influence of anodization time are presented, showing that thick p+ type porous silicon layers are non-homogeneous. The DSC technique which was used for the first time to investigate fluids confined in porous silicon, enables us to deduce original information, such as the pore size distribution, the decrease in the freezing temperature of confined water, and the thickness of non-freezing liquid layer at the pore wall surface.

We report differential scanning calorimetry (DSC) experiments which were performed on organic fluids confined in porous silicon samples. The transition temperature of the confined fluid was found to be lower when compared to the bulk fluid. The effect of the doping level of Si substrate, HF dissolution or anodization time on the DSC results are also presented. Some hints for the thermodynamic interpretation of such an experiment are finally given. © 1997 Elsevier Science S.A.

X-ray-diffraction observations of strains induced by vapor adsorption are reported for porous silicon single-crystal samples. Two types of porous silicon ($p$ and ${p}^{+}$) with very different pore structure are investigated. A low-pressure contraction is observed in $p$-type samples with spherical pores of about 3-nm diameter. In ${p}^{+}$-type samples, where the pores are cylindrical with a larger diameter of about 10 nm, a minimum of the lattice parameter versus the vapor pressure is observed when capillary condensation occurs with a distinct hysteresis between increasing and decreasing vapor pressure. Finally, an expansion is observed for complete wetting. These results are discussed for the different pressure ranges in relation to previous experimental and theoretical studies on adsorption strains. The analogous features observed for very different materials could have a common origin. The expansion is easily explained by the decrease of surface energy due to adsorption and wetting. It appears that the low-pressure contraction is partially related to the attractive van der Waals interactions induced by vapor adsorption in nanometer-size cavities. The softening of the elastic constants observed in porous silicon is discussed in order to explain the magnitude of the observed strains.

A systematic study of porous silicon anodic oxidation is reported. We have studied the evolution of the lattice parameter versus oxidation levels for p‐ and p+‐type materials by using high‐resolution x‐ray diffraction, which gives a determination of the strains of the porous layer. The analysis of an asymmetric reflection enables us to measure the lattice parameter parallel to the surface. Moreover a diffuse scattering, observed at the bottom of the Bragg peaks, comes from the porous structure. The study of this diffuse scattering with reciprocal space maps gives information about the pore size and shape. It is shown that the evolution of the lattice mismatch parameter is related to the surface stress variations. After a review of previous works on porous silicon strains and on surface stresses of silicon we discuss the origin of the strains of as‐formed and oxidized porous silicon.

We review previous X-ray diffraction experiments on porous silicon, giving a determination of porous layer strain. The results of our X-ray measurements of the strain of as-formed and anodically oxidized samples are presented; the diffraction curves of thin layers and of superlattices and the strain induced by liquid wetting and vapour adsorption have been measured. The size and shape of silicon crystallites can be determined from the X-ray diffraction pattern, in particular by using reciprocal space maps.

High-resolution X-ray diffraction has been used for the structural characterization of thin single porous silicon (PS) layers and superlattices. Thin PS layers, in the range of 100–1000 nm, exhibit several thickness interfringes, giving evidence for the lateral homogeneity of the layer thickness. For PS superlattices, several satellite reflections are visible in the diffraction pattern. The analysis of these experimental results using simulations allows us to deduce structural information of this new kind of silicon heterostructure.

The effects of the capillary stresses during the drying of p + -type porous silicon (PS) layers are reported. The cracking of the PS layers occurs for samples thicker than a critical thickness value hc. Taking into account the elastic properties of p + -type PS material, a simple model shows that hc varies as (1 − p)3 and 1/γLV2, where p is the porosity and γLV is the surface tension of the drying liquid. A good agreement with experimental results is observed. This study leads also to a very easy and simple method which increases the hc value by a factor of about 25 when using pentane as the drying liquid (instead of water).

The lattice mismatch between the γ and γ′ phases of single-crystal specimens of the nickel-base superalloy AM1 has been measured as a function of temperature by a high-resolution neutron diffraction technique for various treatments and after high-temperature creep deformation. It was observed that the misfit depends on the precipitate morphology. This effect is strongly enhanced for the ‘rafted microstructure’ typical of the crept sample where the value, the sign and the temperature evolution of the misfit measured along and perpendicular to the (001) stress axis are different. Therefore it appears that the relevant structural parameter which characterizes a superalloy family is not the one-dimensional (ID) misfit parameter b but a three-dimensional (3D) parameter such as the relative difference in unit cell volumes of the γ and γ′ phases. The large influence of plastic relaxations is evidenced and a mechanism is proposed to describe the variations with temperature of the various δ values measure...

Des experiences de diffraction de rayons X haute resolution sont effectuees sur des echantillons de silicium poreux (type p + , porosite 40%) de differentes epaisseurs (de 0,03 a 20 μm). Pour les couches les plus epaisses des pics de Bragg fins sont observes, avec des profils proches de ceux donnes par la theorie dynamique de la diffraction. Pour des epaisseurs plus petites (dans le domaine de 0,1 μm) le pic de Bragg de la couche poreuse n'est pas resolu, mais apparait comme un epaulement au pic du substrat. Des franges d'epaisseur sont observees, montrant ainsi que les surfaces de la couche poreuse sont bien definies.

The γ-ray diffraction technique is proposed as a means of detecting and localizing strain in a bulk single grain material. In order to test this non-destructive technique, a single grain nickel-base superalloy submitted to a pure shear creep test is studied. The study is based on comparing a series of rocking curves recorded for the same parts of the sample before and after the shear test. The analysis of the rocking curves allows to detect relative rotations of different zones of the specimen, which results in the definition of a new geometry for the sheared specimen. Moreover, the analysis of the diffraction peaks in relation to the sheared zone shows that γ-ray diffraction is sensitive to straining; the position of the γ-ray diffraction peak is modified and the diffraction peak collapses in the sheared zone. These results supplement the microscopic observations and confirm that the specific microstructure of the single crystal superalloy induces, after straining, a complex redistribution of the macroscopic deformation in the material. Nous avons teste les possibilites offertes par la diffractometrie γ pour detecter et localiser en volume l'ecrouissage dans un echantillon monocristallin massif. Pour cela, nous avons sollicite en fluage en cisaillement une eprouvette monocristalline de superalliage a base de nickel qui presente au centre une zone deformee bien localisee. L'etude a consiste a comparer des series de profils de diffraction γ obtenus avant et apres deformation de l'echantillon. L'analyse des resultats nous a permis de detecter apres l'essai de cisaillement des rotations relatives de differentes regions de l'eprouvette qui nous ont conduit a redefinir une nouvelle geometrie de l'eprouvette de cisaillement. D'autre part, l'analyse des profils de diffraction relatifs a la zone cisaillee a montre que la diffraction γ etait sensible a l'ecrouissage. L'ecrouissage se traduit par un deplacement et un effondrement du pic de diffraction γ dans la zone cisaillee. L'analyse des resultats obtenus par diffraction γ completent les observations microscopiques et confirment que la microstructure specifique des superalliages monocristallins induit une redistribution complexe de la deformation macroscopique au sein du materiau.

A perfect silicon crystal is used at the ESRF as monochromator for monochromatic synchrotron diffraction topography. This monochromator produces a beam with a narrow range of energy, which is not suitable for some experiments. Moreover, the diffracted energy varies spatially on the monochromatic beam section. A solution to overcome the narrow energy range and the wavelength dispersion is the use of a vibrating monochromator. We present in this paper the three-pole electromagnet device used to vibrate, at about 100 Hz, the perfect (110) Si crystal, the results on the homogeneity of the vibrations and the X-ray topographs recorded using this method.

High-resolution x-ray-diffraction experiments show that the lattice parameter of porous-silicon layers expands when wetted by an alcohol or an alkane. This phenomenon is nearly reversible when the alkane is removed while there is a time-dependent drift during alcohol wetting. The experimental results obtained for several alkanes and for two types of samples (p and ${\mathit{p}}^{+}$ type) reveal that the magnitude of the lattice-parameter change is correlated with the size of the nanocrystallites rather than with the nature of the alkane. We propose that the lattice expansion is due to a change of the porous-silicon surface stress induced by wetting.

The photoluminescence of porous silicon (PS) layers boron doped is enhanced by anodic oxidation, which gives rise to an electroluminescence phenomenon in the visible range. The anodic oxidation effects on the structural properties of PS are reported, studying the Bragg peaks and the diffuse scattering by means of X-ray diffraction using synchrotron radiation. The decrease of coherent and diffuse scattering intensity close to the Bragg peaks for an oxidized sample is associated to an increase of the scattering intensity in the whole reciprocal space. At small angle values, an isotropic bump is observed which corresponds to the presence of a thin SiO 2 layer at the crystallites surface.

The results of coherent and diffuse X-ray scattering measurements of electroluminescent p+ porous silicon of 60% porosity, obtained by an anodic oxidation are reported. Double-crystal diffraction experiments give information on the modification of the nanostructure as a function of the oxidation time (tox) for a constant current density. The mismatch between the lattice parameters of the porous layer and of the substrate increases linearly for small values of tox, but it is nearly independent of tox for tox > 500s. The change between these two regimes corresponds to the end of the electroluminescence.

T cell recognition of the quaternary structure of human chorionic gonadotropin (hCG), resulting from the association between its alpha (hCG-alpha) and beta (hCG-beta) subunits, was analyzed using hCG-alpha and hCG-beta T cell hybridomas produced in BALB/c mice. First, the fine specificity of these T cell hybridomas was determined, enabling us to divide hCG-alpha-specific T cell hybridomas into two groups. Group I recognized the hCG-alpha(61-81) region, and group II responded to the hCG-alpha(50-70) part of the molecule. Two groups of hCG-beta-specific T cell hybridomas, designated groups III and IV, were analyzed and found to respond to the C- and the N-terminal parts of the hCG-beta(1-22) peptide, respectively. Moreover, we observed that the nature of APC influenced Ag recognition by hCG-beta T cell hybridomas from group IV, but not by other selected T cell hybridomas. We then showed that recognition of the hCG alpha/beta dimer by alpha-specific T cell hybridomas was dramatically reduced compared to both free hCG-alpha and heat-dissociated hCG alpha/beta molecules. In contrast, hCG-beta hybridomas exhibited comparable responses to the free beta subunit and the hCG dimer. Experiments using a dimeric molecule assembled from the alpha-subunit of human follicle-stimulating hormone, which is identical to hCG-alpha, and the beta-subunit of human follicle-stimulating hormone, which is homologous to hCG-beta, confirmed that the three-dimensional structure of the complex rather than the primary structure of the beta-subunit plays a critical role in the processing pathway. Finally, kinetic experiments showed that the presentation of hCG-alpha T cell epitopes differed depending upon whether the alpha-subunit was in its free or combined form. In contrast, the kinetic expression of hCG-beta T cell epitopes appeared to be independent of the quaternary structure of hCG. Thus, conformational alterations resulting from the alpha/beta subunit association mainly influenced processing of the alpha-subunit in its complexed form, rather than processing of the combined beta-subunit. The effect of protein-quaternary structure on T cell recognition may represent a new element in our understanding of the processing and presentation of oligomeric molecules.

During first metal level interconnects fabrication, a controlled modification of the electro-deposited copper over-deposition (overburden) is performed using a partial chemical-mechanical polishing (CMP) step. Next, copper microstructure is stabilized with a short duration hot-plate anneal. Overburden is then removed during CMP end-of-step. Ionic microscopy and EBSD observations of overburden thickness reduction reveal that copper grain growth occurs differently, according to patterned geometries and with a strong texture, as observed in modified films. Reduction of overburden thickness also reveals the capacity of anneal temperature to impact electrical performances. Reliability is impacted for thinnest wires.

Recent results of a two-dimensional finite−element modelling of the elastic distortions resulting from the lattice mismatch between γ− and γ−phases have been used to estimate the relative contribution of internal stresses to the broadening of γ-ray diffraction peaks, which has been observed at high temperatures in the case of some nickel-based superalloy single crystals. In the case of CMSX-2 alloy, it is found that the magnitude of the broadening of {220} and {200} peaks calculated when taking the elastic distortions into account is in good agreement with the experimental observations.

The sintering of both a powder with a wide particle size distribution (0–63 μm) and of a powder with artificially created pores is investigated by coupling in situ X‐ray microtomography observations with Discrete Element simulations. The micro structure evolution of the copper particles is observed by microtomography all along a typical sintering cycle at 1050° C at the European Synchrotron Research Facilities (ESRF, Grenoble, France). A quantitative analysis of the 3D images provides original data on interparticle indentation, coordination and particle displacements throughout sintering. In parallel, the sintering of similar powder systems has been simulated with a discrete element code which incorporates appropriate sintering contact laws from the literature. The initial numerical packing is generated directly from the 3D microtomography images or alternatively from a random set of particles with the same size distribution. The comparison between the information drawn from the simulations and the one ob...

Our previous study on teratocarcinoma cells suggested the role of human parathyroid hormone (hPTH) in early development of the placenta. The purpose of this study was to evaluate the possible role of hPTH on the functions of first trimester trophoblast cells. Adenylate cyclase activity in crude membranes from first trimester human placental villous tissue is stimulated 2-fold by hPTH (1-34) (10(-6) mol.l-1) from 265 +/- 32 to 532 +/- 80 pmol of cAMP/mg protein/15 min. A similar stimulation of adenylate cyclase is observed in human term placental villous tissue but not in 3 different choriocarcinoma cell lines. In order to evaluate the possible role of hPTH on the functions of first trimester human trophoblast cells, these cells were isolated by dispase and cultured (2 x 10(5) cells per plate) in DMEM supplemented with 20% fetal calf serum with or without 100 ng/ml of epidermal growth factor (EGF), for 4 d. On d 2 of culture, hPTH (10(-7) mol.l-1) stimulates cAMP production of these cells from 0.52 +/- 0.2 to 2.58 +/- 0.57 pmol.h-1 per 10(6) cells (mean +/- SEM). As compared to control (30 ng/ml), the output of hCG is increased by 1.5- (NS), 2- (P less than 0.01) and 3- (P less than 0.01) fold by EGF, hPTH, and hPTH added with EGF, respectively. Dibutyryl cAMP (10(-3) mol.l-1) increased hCG secretion by 3-fold (P less than 0.05). EGF and hPTH added separately or together significantly stimulated (P less than 0.01) the secretion of free alpha subunit 2-fold from 35 ng/ml to 70 ng/ml. In contrast, hPTH and EGF added separately did not change the secretion of free beta hCG. However, added together, they significantly increased (P less than 0.01) the secretion of free beta hCG after 48 h of culture, maximal stimulation (2.5 fold) being observed at d 4 of culture. In conclusion, human trophoblast cells are target cells for hPTH. hPTH acts in association with EGF in promoting expression of endocrine activity of these cells, such as hCG secretion. Trophoblast cells provide a model for the study of the cooperative effect between a peptide hormone and a growth factor in the regulation of endocrine function.

Un modele numerique permettant de traiter les regimes d'ecoulements transitoires et periodiques en conduite tronconique est presente dans cette etude. La methode de resolution mise au point peut etre appliquee aux modeles newtoniens generalises ; un modele a quatre parametres, plus adapte que la loi classique d'Ostwald aux comportements reels, est considere pour illustrer l'utilisation de cette methode. L'etude a permis de mettre en evidence certaines particularites associees a ces types d'ecoulements.

Radionuclide lymphoscintigraphy (RNL) has progressively superseded lymphangiography and may be considered as the most advanced method for the assessment of the limb lymphatic system (1, 2).As a safe, noninvasive, and physiological method, RNL is commonly used in lymphology for the evaluation of limb lymphedemas and in oncology for the detection of the sentinel node (SN) (3, 4).However, conventional planar imaging sometimes failed to preoperatively identify the exact localization of the detected lymph nodes (5). Since 2000 (6), hybrid cameras combining a dual head gamma camera with a low-dose radiograph tube mounted on the same gantry were developed, and image fusion has been successfully introduced in clinical practice.We report our experience of this new imaging method in lymphology and oncology, particularly for the SN detection in patients with breast cancer.

We report the first in situ results of deformation during grain boundary penetration in the A(1)/Ga system, obtained with a novel, nondestructive hard x-ray synchrotron projection microscopy technique. Focusing the beam to a state-of-the-art spot size of 90 x 90 nm(2), we demonstrate that penetration is accompanied by continuous relative separation of the Al grains of the same final amplitude as the final Ga layer thickness in the absence of external stress. The formation of nanometric intergranular liquid layers is originated by a crack propagation process and inherently implies the presence of weak stress levels.

We report the first in situ results of deformation during grain boundary penetration in the A(1)/Ga system, obtained with a novel, nondestructive hard x-ray synchrotron projection microscopy technique. Focusing the beam to a state-of-the-art spot size of 90 x 90 nm(2), we demonstrate that penetration is accompanied by continuous relative separation of the Al grains of the same final amplitude as the final Ga layer thickness in the absence of external stress. The formation of nanometric intergranular liquid layers is originated by a crack propagation process and inherently implies the presence of weak stress levels.

The phenomenon of grain boundary penetration (GBP) of liquid Ga along grain boundaries (GB) of Al bicrystals is investigated by synchrotron radiation X-ray microradiography. From the three different types of bicrystals studied, only the one with the highest GB energy showed GBP in the absence of applied external stress. In situ observations of the penetration process reveal a linear propagation of the penetration front, accompanied by a continuous thickening of the wedge-shaped Ga layer in the GB. The experimental results demonstrate that GBP kinetics are strongly influenced by very weak levels of stress and tend to indicate that such stresses may be a prerequisite for the formation of nanometric penetration layers.

The process of grain boundary penetration of liquid Ga in Al polycrystals is characterized by synchrotron radiation X-ray microradiography. This experimental technique allows for non-destructive in situ characterization of dynamic processes in the bulk of millimetric size Al samples. Ga wetting layers as thin as 5–20 nm can be detected inside grain boundaries (GBs) which are favorably inclined with respect to the X-ray beam.The penetration process can be divided into three characteristic steps: (1) propagation and simultaneous thickening of the liquid film, (2) thickening discontinuities with fast propagation rates (higher than 5 mm/s) and (3) saturation of the layer thickness. Discontinuities can be attributed to the formation of intergranular cracks and result in rapid transfer and redistribution of the Ga along the GB network. Experimental results are strongly influenced by stress, even at very low stress levels.

High resolution X-ray measurements of the variations in the lattice parameter of p-type porous silicon produced by wetting or vapour adsorption are reported. While pentane wetting produces only a lattice expansion, pentane vapour adsorption gives a more complex behaviour: with increasing vapour pressure there is first a lattice contraction, followed by an expansion. These results are discussed in relation to vapour adsorption mechanisms.