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A new genus Ami Pérez-Miles is proposed for six new species: A. caxiuana Pérez-Miles, Miglio & Bonaldo, from Caxiuanã National Forest, Pará, Brasil, the type species; A. yupanquii Pérez-Miles, Gabriel & Gallon, from the area of Puyo, Equador; A. bladesi Pérez-Miles, Gabriel & Gallon, from Isla Colón, Panamá; A. pijaos Jimenez & Bertani, from Ibagué, Tolima, Colombia; A. amazonica Jimenez & Bertani, from Leticia, Amazonas, Colombia; and A. weinmanni PérezMiles, from La Azulita, Apure, Venezuela. Avicularia obscura (Ausserer 1875) is transferred to Ami and re-diagnosed. Diagnostic characters of Ami are the modification of Type I urticating hairs, with unusually longer area b, and one or two subconical processes on retrolateral face of male palpal tibiae. Females of Ami differ further from those of other theraphosid genera by their highly characteristic spermathecae: paired ventral receptacles attached to an almost discrete, semicircular, sclerotized back-plate.

Low birth weight and length for gestational age are associated with a high risk of short stature and metabolic syndrome in adulthood. The mechanisms that link prenatal growth to adult stature and metabolic syndrome have not yet been entirely clarified. The aim of our study was to evaluate the relationship between standardized anthropometric measures at birth and insulin-like growth factor (IGF)-I, IGF-II, insulin, adiponectin, and non-esterified fatty acid (NEFA) cord blood levels in the general population. One hundred fifty-eight random newborn subjects (77F, 81M) from Genoa, Italy, were analyzed. Anthropometric parameters were measured and standardized according to standard Italian tables. Insulin values were treated as categorical, since in several cases the results fell below detection cut-off. Mean birth weight was 3,214.23#x2213;488.99 gr and mean length was 49.82#x2213;2.17 cm. Females had higher mean IGF-I (p=0.04), and were more likely to have insulin values either2#956;U/ml or4.5#956;U/ml (p= 0.04) compared to males. Weight and length SD scores (SDS) were higher in subjects with elevated insulin levels (p=0.002). A moderate correlation was found between weight and IGF-II (r=0.354). Multivariable analysis demonstrated that standardized birth weight was associated with IGFII and insulin values. Our data highlight the importance of IGF-II in fetal growth and suggest that gender differences should be taken into consideration when evaluating prenatal growth.

The growth of multi-layer germanium-tin (GeSn) quantum wells offers an intriguing pathway towards the integration of lasers in a CMOS platform. An important step in growing high quality quantum well interfaces is the formation of an initial wetting layer. However, key atomic-scale details of this process have not previously been discussed. We use scanning tunneling microscopy combined with density functional theory to study the deposition of Sn on Ge(1 0 0) at room temperature over a coverage range of 0.01 to 1.24 monolayers. We demonstrate the formation of a sub-2% Ge content GeSn wetting layer from three atomic-scale characteristic ad-dimer structural components, and show that small quantities of Sn incorporate into the Ge surface forming two atomic configurations. The ratio of the ad-dimer structures changes with increasing Sn coverage, indicating a change in growth kinetics. At sub-monolayer coverage, the least densely packing ad-dimer structure is most abundant. As the layer closes, forming a two-dimensional wetting layer, the more densely packing ad-dimer structure become dominant. These results demonstrate the capability to form an atomically smooth wetting layer at room temperature, and provide critical atomic-scale insights for the optimization of growth processes of GeSn multi-quantum-wells to meet the quality requirements of optical GeSn-based devices.

In this paper, we show that lateral arrangement of Ge/Si(00 1) self-assembled islands in a square array oriented along the [100]-[0 10] directions can be obtained through the lateral displacement of the islands themselves. We found that when the deposited islands are exposed to an external silicon flux, the impinging silicon atoms induce Ge-Si intermixing resulting in island shape transformation from domes to large pyramids. This transformation leads to an array of closely spaced islands interacting elastically among themselves through the substrate. By means of atomistic simulations we demonstrate that this elastic repulsion drives a net flux of Ge and Si atoms from one side to the other side of the islands, leading to a lateral displacement of the whole island. This displacement ends when the two islands are sufficiently far away, or when another island is approached during the motion. In a dense ensemble of islands, this mechanism drives the tendency to order observed experimentally. (C) 2006 Elsevier Ltd. All rights reserved.

We present an investigation of the structural quality of arrays of 3C-SiC micropillars and microridges grown epitaxially on deeply etched Si(0 0 1) substrates offcut towards [1 1 0]. Using high resolution X-ray diffraction with reciprocal space mapping and optical as well as scanning electron microscopy, we obtain information about the stacking fault (SF) formation in different crystallographic directions. The SF density is strongly correlated with the microcrystal size and orientation and a reduction of the SF density is found in the [1 1 1] and [1 −1 1] directions. No variation of the average SF size was detected for varying SiC microcrystal size and shape.

Recently synthesized hexagonal group IV materials are a promising platform to realize efficient light emission that is closely integrated with electronics. A high crystal quality is essential to assess the intrinsic electronic and optical properties of these materials unaffected by structural defects. Here, we identify a previously unknown partial planar defect in materials with a type I3 basal stacking fault and investigate its structural and electronic properties. Electron microscopy and atomistic modeling are used to reconstruct and visualize this stacking fault and its terminating dislocations in the crystal. From band structure calculations coupled to photoluminescence measurements, we conclude that the I3 defect does not create states within the hex-Ge and hex-Si band gap. Therefore, the defect is not detrimental to the optoelectronic properties of the hex-SiGe materials family. Finally, highlighting the properties of this defect can be of great interest to the community of hex-III-Ns, where this defect is also present., This project has received funding from the European Union’s Horizon 2020 research and innovation program under Grant agreement no. 735008 (SiLAS). I.Z. acknowledges financial support from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Grant agreement no. 756365). M.D.L. acknowledges support from the Swiss National Science Foundation Ambizione grant (Grant no. PZ00P2_179801). R.R. acknowledges financial support by the Ministerio de Economía, Industria y Competitividad (MINECO) under Grant FEDER-MAT2017–90024-P, by the Severo Ochoa Centres of Excellence Program under Grant SEV-2015–049,6 and by the Generalitat de Catalunya under Grant no. 2017 SGR 1506. L.S. acknowledges financial support from the China Scholarship Council. S.B. acknowledges funding from the Volkswagen Stiftung (Momentum) through the project “Dandelion” and the DFG through projects SFB-1375 and BO4280/8-1. Computational resources were also provided by the Leibniz Supercomputing Center through projects pr48je and pr62ja.

Classical molecular dynamics simulations are used to investigate the 3D evolution of stacking faults (SFs), including the partial dislocation (PD) loops enclosing them, during growth of 3C-SiC layers on Si(001). It is shown that the evolution of single PD loops releasing tensile strain during the initial carbonization stage, commonly preceding 3C-SiC deposition, leads to the formation of experimentally observed V- or Δ-shaped SFs, the key role being played by the differences in the mobilities between Si- and C-terminated PD segments. Nucleation in the adjacent planes of PD loops takes place at later stage of 3C-SiC deposition, when slightly compressive-strain conditions are present. It is shown that such a process very efficiently decreases the elastic energy of the 3C-SiC crystal. The maximum energy decrease is obtained via the formation of triple SFs with common boundaries made up by PD loops yielding a zero total Burgers vector. Obtained results explain the experimentally observed relative abundance of compact microtwin regions in 3C-SiC layers as compared with the other SF-related defects.

3C-SiC epitaxially grown on Si displays a large wealth of extended defects. In particular, single, double and triple stacking faults (SFs) are observed to coexist in several experiments. Overabundance of defects has so far limited the exploitation of 3C-SiC/Si for power electronics, in spite of its several ideal properties (mainly in terms of the wide gap, high breakdown fields and thermal properties) and the possibility of direct integration in the Si technology. Here we use a multiscale approach, based on both classical molecular dynamics (MD) simulations and first-principles calculations, for the in-depth investigation of the origin, nature and properties of most common 3C-SiC/Si(001) extended defects. Our MD simulations reveal a natural path for the formation of partial dislocation complexes terminating both double and triple SFs. The MD results are used as an input for superior DFT calculations, allowing us to better determine the core structure and to investigate electronic properties. It turns out that the partial dislocation complexes terminating double and triple SFs are responsible for the introduction of electronic states significantly filling the band gap. On the other hand, individual partial dislocations terminating single SFs only induce states very close to the gap edge. We conclude that partial dislocation complexes, in particular the most abundant triple ones, are killer defects in terms of favoring leakage currents. Suggestions coming from theory/simulations for devising a strategy to lower their occurrence are discussed.

While the Ge(0 0 1) surface has been extensively studied, it is still debated whether it is of conducting or semiconducting nature at room temperature. The evidence collected by angle-resolved photoelectron spectroscopy experiments in the past has led to the preliminary attribution of a semiconducting nature at room temperature. In contrast, we show in this work that the pristine Ge(0 0 1) surface is conducting at room temperature by using temperature-dependent angle-resolved photoelectron spectroscopy, scanning tunneling microscopy and first principles calculations. Specifically, a surface band located ∼200 meV above the valence band maximum has been observed at room temperature. This surface band shows anisotropic dispersions along the [0 1 0] and [1 1 0] directions, but it disappears at lower measurement temperature, which indicates its occupation by thermally excited electrons. State-of-the-art density functional theory calculations undoubtedly attribute this surface band to the unoccupied π*-band formed by dangling bonds on the c(4 × 2) surface reconstruction, while evidencing fundamental differences with the p(2 × 1) reconstruction. Furthermore, the calculations demonstrate that the valence band structure observed in angle-resolved photoelectron spectroscopy experiments arise from projected bulk states and is thus insensitive to surface contamination. Our results contribute to the fundamental knowledge of the Ge(0 0 1) surface and to a better understanding of its role in micro- and opto-electronic devices.

The scanning X-ray nanodiffraction technique is used to reconstruct the three-dimensional distribution of lattice strain and Ge concentration in compositionally graded Si1−x Ge x microcrystals grown epitaxially on Si pillars. The reconstructed crystal shape qualitatively agrees with scanning electron micrographs and the calculated three-dimensional distribution of lattice tilt quantitatively matches finite-element method simulations. The grading of the Ge content obtained from reciprocal-space maps corresponds to the nominal grading of the epitaxial growth recipe. The X-ray measurements confirm strain calculations, according to which the lattice curvature of the microcrystals is dominated by the misfit strain, while the thermal strain contributes negligibly. The nanodiffraction experiments also indicate that the strain in narrow microcrystals on 2 × 2 µm Si pillars is relaxed purely elastically, while in wider microcrystals on 5 × 5 µm Si pillars, plastic relaxation by means of dislocations sets in. This confirms previous work on these structures using transmission electron microscopy and defect etching.

The presence of extended bi-dimensional defects is one of the key issues that hinder the use of wide band-gap materials hetero-epitaxially grown on silicon. In this work, we investigate, by STEM measurements and molecular dynamic simulations, the structure of two of the most important extended defect affecting the properties of cubic silicon carbide, 3C-SiC, hetero-epitaxially grown on (001) silicon substrates: (1) stacking faults (SFs) with their bounding threading dislocation arms, even along with unusual directions, and (2) inverted domain boundaries (IDBs). We found that these two defects are strictly correlated: IDBs lying in {111} planes are intrinsically coupled to one or more SFs. Moreover, we observed that threading partial dislocations (PDs), limiting the SFs, appear to have non-conventional line directions, such as [112], [123], and [134]. Molecular dynamics simulations show that [110] and [112] directions allow for stable dislocation structures, while in the unusual [123] and [134] directions, the PDs are composed of zig-zag dislocation lines in the [112] and [110] directions.

Extending the functionality of ubiquitous Si-based microelectronic devices often requires combining materials with different lattice parameters and thermal expansion coefficients. In this paper, scanning X-ray nanodiffraction is used to map the lattice bending produced by thermal strain relaxation in heteroepitaxial Ge microcrystals of various heights grown on high aspect ratio Si pillars. The local crystal lattice tilt and curvature are obtained from experimental three-dimensional reciprocal space maps and compared with diffraction patterns simulated by means of the finite element method. The simulations are in good agreement with the experimental data for various positions of the focused X-ray beam inside a Ge microcrystal. Both experiment and simulations reveal that the crystal lattice bending induced by thermal strain relaxation vanishes with increasing Ge crystal height.

The growth morphology of epitaxial 3C-SiC crystals grown on hexagonal pillars deeply etched into Si(111) substrates is presented. Different growth velocities of side facets let the top crystal facet evolve from hexagonal towards triangular shape during growth. The lateral size and separation between Si pillars determine the onset of fusion between neighboring crystals during growth at a height tailoring of which is crucial to reduce the stacking fault (SF) density of the coalesced surface. A density of 3400 cm-1 was observed for a coalesced surface, compared to 8100 cm-1 for layers grown on unpatterned area. Intermediate partial fusion of neighboring crystals is shown as well as a surface of fully coalesced crystals.

The stacking faults (SFs) in 3C-SiC epitaxially grown on ridges deeply etched into Si (001) substrates offcut towards [110] were quantitatively analyzed by electron microscopy and X-ray diffraction. A significant reduction of SF density with respect to planar material was observed for the {111} planes parallel to the ridges. The highest SF density was found in the (-1-11) plane. A previously observed defect was identified as twins by electron backscatter diffraction.

Compositional segregation is commonly observed during the growth of III-V alloys in core-shell nanowires. Nanometer-thin stripes, enriched in one of the alloy components, are observed along the six directions perpendicular to the [1 1 1]-wire axis, departing from the core to the outer shell edges in between the {1 1 0} faceted sidewalls. While it has been well established that the phenomenon occurs because of the different mobility of the alloy components, the actual mechanisms by which it happens are yet unclear. A phase-field model, coupling deposition and surface diffusion dynamics, is here developed to inspect the simultaneous evolution of the shell morphology and composition during growth. Both surface energy anisotropy and orientation-dependent growth rates are taken into account to identify their different role. Simulations reveal that the observed segregation is mainly triggered by the enhanced growth rate at the facet edges, while surface anisotropy keeps the stripes thin. Polarity effects are also included to differentiate the behavior between A and B orientations, so to reproduce the experimental observation of a 3-fold symmetry.

The exceptionally large thermal strain in few-micrometers-thick 3C-SiC films on Si(111), causing severe wafer bending and cracking, is demonstrated to be elastically quenched by substrate patterning in finite arrays of Si micro-pillars, sufficiently large in aspect ratio to allow for lateral pillar tilting, both by simulations and by preliminary experiments. In suspended SiC patches, the mechanical problem is addressed by finite element method: both the strain relaxation and the wafer curvature are calculated at different pillar height, array size, and film thickness. Patches as large as required by power electronic devices (500–1000 μm in size) show a remarkable residual strain in the central area, unless the pillar aspect ratio is made sufficiently large to allow peripheral pillars to accommodate the full film retraction. A sublinear relationship between the pillar aspect ratio and the patch size, guaranteeing a minimal curvature radius, as required for wafer processing and micro-crack prevention, is shown to be valid for any heteroepitaxial system., Journal of Applied Physics, 123 (18), ISSN:0021-8979, ISSN:1089-7550

We present an innovative approach to integrate arrays of isolated, strain-free GaN crystals on patterned Si substrates. First, micrometer-sized pillars are patterned onto Si(0 0 1) substrates. Subsequently, 2.5 μm Si substrates are deposited by low-energy plasma-enhanced chemical vapor deposition, forming crystals mostly bounded by {1 1 1}, {1 1 3}, and {15 3 23} facets. Plasma-assisted molecular beam epitaxy is then used for GaN deposition. GaN crystals with slanted {0 0 0 1} facets having a root-mean-square surface roughness of 0.7 nm are obtained for a deposited material thickness of >3 μm. Microphotoluminescence measurements performed at room and cryogenic temperature show no yellow luminescence and a neutral donor-bound A exciton transition at 3.471 eV (10 K) with a full width at half-maximum of 10 meV. Microphotoluminescence and micro-Raman spectra reveal that GaN grown on Si pillars is strain-free. Our results indicate that the shape of GaN crystals can be tuned by the pattern periodicity and that a reduction of threading dislocations is achieved in their top part.

We present a method for monolithically integrating mismatched semiconductor materials with Si, coined three-dimensional (3D) heteroepitaxy. The method comprises the replacement of conventional, continuous epilayers by dense arrays of strain- and defect-free, micron-sized crystals. The crystals are formed by a combination of deep-patterning of the Si substrates and self-limited lateral expansion during the epitaxial growth. Consequently, the longstanding issues of crack formation and wafer bowing can be avoided. Moreover, threading dislocations can be eliminated by appropriately choosing pattern sizes, layer thicknesses and surface morphology, the latter being dependent on the growth temperature. We show this approach to be valid for various material combinations, pattern geometries and substrate orientations. We demonstrate that Ge crystals evolve into perfect structures away from the heavily dislocated interface with Si, by using a synchrotron X-ray beam focused to a spot a few hundred nanometers in size and by recording 3D reciprocal space maps along their height. Room temperature photoluminescence (PL) experiments reveal that the interband integrated PL intensity of the Ge crystals is enhanced by almost three orders of magnitude with respect to that of Ge epilayers directly grown on flat Si substrates. Electrical measurements performed on single heterojunction diodes formed between 3D Ge crystals and the Si substrate exhibit rectifying behavior with dark currents of the order of 1 mA/cm2. For GaAs the thermal strain relaxation as a function of pattern size is similar to that found for group IV materials. Significant differences exist, however, in the evolution of crystal morphology with pattern size, which more and more tends to a pyramidal shape defined by stable {111} facets with decreasing width of the Si pillars. © 2013 Elsevier B.V.

An important issue in the technology of cubic SiC (3C-SiC) material for electronic device applications is to understand the behavior of extended defects such as partial dislocation complexes and stacking faults. Atomistic simulations using molecular dynamics (MD) are an efficient tool to tackle this issue for large systems at comparatively low computation cost. At this, proper choice of MD potential is imperative to ensure the reliability of the simulation predictions. In this work, we compare the evolution of extended defects in 3C-SiC obtained by molecular dynamics simulations with Tersoff, analytical bond order, and Vashishta potentials. Key aspects of this evolution are considered including the dissociation of 60° perfect dislocations in pairs of 30O and 90O partials as well as the dependence of the partial dislocation velocity on the Burgers vector and the atomic composition of core. Tersoff potential has been found to be less appropriate in describing the dislocation behavior in 3C-SiC as compared to two other potentials, which in their turn provide qualitatively equivalent predictions. The Vashishta potential predicts much faster defect dynamics than the analytical bond order potential (ABOP). It can be applied therefore to describe the large-scale evolution of the dislocation systems and stacking faults. On the other hand, ABOP is more precise in predicting local atom arrangements and reconstructions of the dislocation core structures. In this respect, synergetic use of ABOP and Vashishta potential is suggested for the molecular dynamics simulation study of the properties and evolution of extended defects in the 3C-SiC.

In this work, the structure and stability of partial dislocation (PD) complexes terminating double and triple stacking faults in 3C-SiC are studied by molecular dynamics simulations. The stability of PD complexes is demonstrated to depend primarily on the mutual orientations of the Burgers vectors of constituent partial dislocations. The existence of stable complexes consisting of two and three partial dislocations is established. In particular, two types of stable double (or extrinsic) dislocation complexes are revealed formed by two 30&deg, partial dislocations with different orientations of Burgers vectors, or 30&deg, and 90&deg, partial dislocations. Stable triple PD complexes consist of two 30&deg, partial dislocations with different orientations of their Burgers vectors and one 90&deg, partial dislocation, and have a total Burgers vector that is equal to zero. Results of the simulations agree with experimental observations of the stable PD complexes forming incoherent boundaries of twin regions and polytype inclusions in 3C-SiC films.

In this report we present a novel strategy in selective epitaxial growth on top of Si pillars, which results in a tessellated Ge film, composed by self-aligned micron-sized crystals in a maskless process. Modelling by rate equations the morphology evolution of fully facetted crystal profiles is extensively outlined, showing an excellent prediction of the peculiar role played by flux shielding among microcrystals, in the case of dense array configuration. Crack formation and substrate bending, caused by the mismatch in thermal expansion coefficients, are eliminated by the mechanical decoupling among individual microcrystals, which are also shown to be dislocation- and strain-free. The method has been also tested for Si 1− x Ge x alloys, with compositions ranging from pure silicon to pure germanium. There are ample reasons to believe that this approach could be extended to other material combinations and substrate orientations, actually providing a technology platform for several device applications.

In this paper we report a new method for Cu(In,Ga)Se(2) deposition for solar cell application. Differently from the common co-evaporation process, an alterative approach for thin film Cu(In,Ga)Se(2) has been tested: the sputtering deposition of metal elements combined with the selenium evaporation. We have studied the relationships between the growth parameters of our hybrid sputtering/evaporation method and the chemical-physical properties of the CIGS films. The cells are completed with a CdS buffer layer deposited by chemical bath deposition and ZnO + ITO deposited by RF sputtering. Test solar cells of 0.5 cm(2) have shown an efficiency of 10% and 2.5% on glass and stainless steel substrate respectively. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

In this work, an alternative approach for CIGS thin film growth has been tested, which is different from the common co-evaporation process. Such approach consists of sputtering deposition of the metal elements combined with selenium evaporation. This new and easily scalable procedure allows deposition time of the CIGS layer lower than 15 minutes and can be easily applied not only on rigid but also on flexible substrates in a roll to roll configuration, matching industrial application requirements. The relationships between the growth parameters of such hybrid sputtering/evaporation method and the chemical-physical properties of the CIGS films and cells have been studied.

Nanowires have emerged as a promising platform for the development of novel and high-quality heterostructures at large lattice misfit, inaccessible in a thin film configuration. However, despite core-shell nanowires allowing a very efficient elastic release of the misfit strain, the growth of highly uniform arrays of nanowire heterostructures still represents a challenge, for example due to a strain-induced bending morphology. Here we investigate the bending of wurtzite GaP/In x Ga1-xP core-shell nanowires using transmission electron microscopy and energy dispersive x-ray spectroscopy, both in terms of geometric and compositional asymmetry with respect to the longitudinal axis. We compare the experimental data with finite element method simulations in three dimensions, showing that both asymmetries are responsible for the actual bending. Such findings are valid for all lattice-mismatched core-shell nanowire heterostructures based on ternary alloys. Our work provides a quantitative understanding of the bending effect in general while also suggesting a strategy to minimise it.

Silicon-rich SiGe alloys represent a promising platform for the development of large-area single-mode optical waveguides to be integrated in silicon-based optical circuits. We find that SiGe layers epitaxially grown on Si successfully guide radiation with a 1.55 μm wavelength, but, beyond a critical core thickness, their optical properties are strongly affected by the clustering of misfit dislocations at the interface between Si and SiGe, leading to a significant perturbation of the local refractive index. Transmission electron microscopy and micro-Raman spectroscopy, together with finite-element simulations, provide a complete analysis of the impact of dislocations on optical propagation. © 2009 Elsevier B.V. All rights reserved.

Silicon is a promising material for solar cells and optical devices. Among the different growth techniques, Plasma Enhanced CVD (PECVD) attracts particular interest allowing to obtain high quality deposition at significant rates and low substrate temperatures. Controlling the film morphology is key for improving the material optoelectronic properties. In order to be able to relate growth rates and quality of the deposited material to the plasma operating conditions we have developed a detailed plasma-reactor model. The solution of mass, momentum and energy conservation equations in a 2D domain is considered, and eventually coupled to the solution of a discharge model based on a simplified gas phase chemistry. The main novelty of this model are the detailed gas phase and surface kinetic schemes developed. The gas phase model comprises about 30 chemical species involved in more than 80 reactions. Surface reaction probabilities were calculated based on a fully atomistic, dynamical approach. The predictive power of the model against experimental data is demonstrated, and the role of various radicals and ions in determining the film growth is discussed.

SiHx (x = 1,2,3) ions impact on Si(001)(1 x 1):H and Si(001)(2 x 1):H surfaces has been studied by classical molecular dynamic simulations, considering an energetic range for the impinging species from 5 to 15 eV. Despite the initial full H coverage a high sticking coefficient has been obtained for all the species under investigation. A considerable fraction of adsorption events causes H removal from the surface while for other simulations a soft landing mechanism of the ions has been observed. Few representative minima for SiH2/ Si(0 01)(2 x 1):H were re-converged by ab initio calculations in order to check the reliability of our results. (C) 2007 Elsevier B.V. All rights reserved.

The move from dimensional to functional scaling in microelectronics has led to renewed interest toward integration of Ge on Si. In this work, simulation-driven experiments leading to high-quality suspended Ge films on Si pillars are reported. Starting from an array of micrometric Ge crystals, the film is obtained by exploiting their temperature-driven coalescence across nanometric gaps. The merging process is simulated by means of a suitable surface-diffusion model within a phase-field approach. The successful comparison between experimental and simulated data demonstrates that the morphological evolution is driven purely by the lowering of surface-curvature gradients. This allows for fine control over the final morphology to be attained. At fixed annealing time and temperature, perfectly merged films are obtained from Ge crystals grown at low temperature (450 °C), whereas some void regions still persist for crystals grown at higher temperature (500 °C) due to their different initial morphology. The latter condition, however, looks very promising for possible applications. Indeed, scanning tunneling electron microscopy and high-resolution transmission electron microscopy analyses show that, at least during the first stages of merging, the developing film is free from threading dislocations. The present findings, thus, introduce a promising path to integrate Ge layers on Si with a low dislocation density.

We propose an extension of the well-known flat-island approximation in (1 1) dimensions which, while keeping simple analytical relations, allows one to better describe the strain field on the facets of steeper islands, and on the wetting layer between them. The results of atomistic molecular dynamics simulations using the Tersoff potential are used as a benchmark. The simple continuum approach is also shown to predict the correct trend of the strain gradients characterizing closely-spaced interacting islands, which has been recently observed to produce lateral motion of large Ge dots on Si(001). (c) 2006 Elsevier B.V. All rights reserved.

This review emphasizes progress in theoretical simulation and experiments that have been performed in the past years for semiconducting silicides. New fundamental electronic and optical properties of Ca2Si and BaSi 2, recently found RuSi2 phase, ternaries in Fe-Os-Si and Ru-Os-Si systems, β-FeSi2, Mg2Si and CrSi2 with stretched and compressed lattices as well as transport properties of β-FeSi2, ReSi1.75, Ru2Si3 are presented. Prospects for practical applications of semiconducting silicides are discussed. © 2004 Published by Elsevier B.V.

This volume is a collection of papers presented at Symposium K “Group IV Semiconductors Materials Research: Growth, Characterization and Applications to Electronics and Spintronics” at the E-MRS Spring Meeting 2016 held from May 02–06 in Lille, France. During preparation of our symposium we were facing the sad situation that Prof. Jan Vanhellemont, one of the organizers, prematurely died. Jan Vanhellemont was an outstanding materials researcher and the organizers decided, in agreement with the E-MRS conference chairs, to dedicate Symposium K in memoriam to him. A brief overview of his scientific career, covering more than 35 years in semiconductor materials science, is given in the beginning of this volume. The major challenges for fundamental research and technological development are no more confined to bulk silicon and silicon devices only, but to a variety of silicon-based structures, such as Si–Ge alloys, nanostructured and nanocomposite materials, thin and thick films, and heteroepitaxial layers on patterned silicon substrates. Their performances are still driven by defect engineering procedures, novel growth techniques, and advanced diagnostics tools. Point defects and extended defects remain in the center of interest for both electronic and photovoltaic applications, where in some cases their engineering represents a unique option for new functionalities, such as the case of spintronic devices. A special session on spintronics was supported by the Fondazione Cariplo (Milano, Italy). The symposium provided a successful forum for scientists from research institutions and industry from all over the world to discuss recent results and new developments in materials research on group IV elements. In total 80 oral and 43 poster presentations made this symposium a fruitful expert meeting.

After a brief review of the basic properties of TiSi 2 phases recently obtained by molecular dynamics simulations, we show the self-diffusing species at high temperatures in both the C54 and C49 structures to be silicon, by hopping through a first neighbours network. The kinetic parameters and the diffusion paths for Si diffusion by vacancies and interstitials are reported, pointing out that diffusion in the C49 structure by SiI vacancies is strongly favoured, due to the very low formation energy they display.

Tight-binding (TB) potentials allow for a straightforward separation of the binding and repulsive contributions in the total energy. This issue can be used in molecular dynamics runs to correlate the local atomic structure to the diffusion paths and the activation energies of silicon mobility in TiSi2, which is the most common material for metallisations and local interconnects in microelectronic devices. In this work we focus on the self-diffusion process at high temperature and a relation between the crystal structures and the diffusion paths for the two competing phases is drawn. © 2001 Elsevier Science B.V. All rights reserved.

A patient with ophthalmoplegic migraine is described, and his computed tomography and magnetic resonance imaging findings are discussed. According to our results, triad migraine, third nerve palsy, and focal enhancement of an enlarged third cranial nerve at the root exit zone should be considered pathognomonic of the disease, and further examinations should be avoided. Pathogenetic theories of the disease are discussed, and we suggest a new pathogenetic theory.

In this paper we show that the driving force leading to the metal-semiconductor structural phase transition occurring in epitaxial FeSi2 with film thickness, originates from a local Jahn-Teller distortion. This effect can be straightforwardly seen by the analysis of the site-projected density of states during a variable cell molecular dynamics for the bulk configuration. We point out that the evolution of the local density of states is a reliable and powerful tool solely provided by tight-binding molecular dynamics. [S0163-1829(99)00905-4].