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Crystallization processes of amorphous germanium–tin (GeSn) under low-energy electron-beam irradiation were examined using transmission electron microscopy (TEM). Freestanding amorphous GeSn thin films were irradiated with a 100 keV electron beam at room temperature. The amorphous GeSn was athermally crystallized by electron-beam irradiation, when the electron flux exceeded the critical value. Heterogeneous structures consisting of nano- and micro-crystallites were formed after crystallization of amorphous GeSn with ∼24 at. % Sn in the as-sputtered amorphous state. In situ TEM observations of structural changes under electron-beam irradiation revealed that random nucleation and growth of nanocrystallites occur at the early stage of crystallization, followed by rapid formation of micro-grains surrounding the nanocrystals. It has been suggested that the growth of micro-grains progresses via supercooled liquid Sn at the amorphous/crystalline interface. The resultant GeSn grains with a size of a few micrometers contained ∼15 at. % Sn, much larger than the solubility limit of Sn in Ge (∼1 at. % Sn). [ABSTRACT FROM AUTHOR]

• The effect of cavities on recrystallization growth in SiC was investigated. • The formed cavities can retard the epitaxial growth. • Nanocrystalline SiC was observed in the cavity layer. The effect of cavities on recrystallization growth of amorphous SiC induced by a high fluence He implantation was investigated. 300 keV He ions were used to implant the 6H-SiC (0001) wafer to a fluence of 4.4 × 1017/cm2 at room temperature. A buried amorphous layer with a width of approximately 468 nm was formed. Moreover, many spherical bubbles with diameters over 25 nm were observed by transmission electron microscopy. Recrystallization of the buried amorphous layer was visible after 900 °C annealing for 30 min. Some irregular cavities were found in the damaged layer. The recrystallization started from the amorphous/crystalline interface, and the formed cavities retarded the epitaxial growth. Nanocrystalline SiC was formed in the cavity layer. Extended defects were also characterized by transmission electron microscopy. The research results will give an insight into the recrystallization process in amorphous SiC. [ABSTRACT FROM AUTHOR]

[Display omitted] • The crystallization process of amorphous YAG oxide is investigated from an atomic point of view. • The crystallization proceeds on the surface and interior of the amorphous YAG separately, and which show the preferential crystallization of the surface atoms. • Some atoms in the amorphous phase were controlled by the periodic potential field of the crystal atoms and produced dynamically changing semi-ordered structures at the amorphous/crystalline interface with mainly concentrated within 1–2 nm from the interface. The transformation from amorphous materials to crystals and the corresponding microscopic mechanism have become a research focus in materials science, condensed matter physics, and biophysics etc. In this paper, taking Y 3 Al 5 O 12 (YAG) as an example, the crystallization process of amorphous YAG oxide is investigated from an atomic point of view through the combination of spherical aberration-corrected transmission electron microscopy (SCTEM) with an in situ heating method, and the morphology and structural evolution of the surface and interface are explored. It is observed that the crystallization proceeds on the surface and interior of the amorphous YAG separately. Through atomic-scale imaging, it is determined that semi-ordered structures are formed in a few atomic layers at the amorphous/crystalline interface and that the structural transformation process from the amorphous to the semi-ordered state and then to the crystal structure may be the main reason for the multiple stages of the crystallization of amorphous oxides. This study demonstrates the mechanism of the amorphous-to-crystal transformation on the atomic scale and contributes to gaining a better understanding of the crystallization process of bulk oxides, especially complex metal oxides. [ABSTRACT FROM AUTHOR]

The amorphous (a-) CoFeB/crystalline (c-) MgO based tunneling system interface has been studied by means of quantitative high resolution transmission electron microscopy from atomic to micrometer length scales with increasing annealing temperatures. On the micron scale an irregular nucleation is found. On the atomic scale a long-range order is induced by the MgO interface, explaining the high tunnel magnetoresistance values >100% even for not fully crystallized CoFeB/MgO/CoFeB tunnel junctions. [ABSTRACT FROM AUTHOR]

Local atomic structure of liquid and amorphous Al 80 − x T x Si 20 (where T = Fe, Co, Ni and x = 10, 15) alloys has been studied by X-ray diffraction (XRD) and molecular dynamics simulations. Chemical short-range order in the liquid and amorphous alloys has been found to be similar to that in the corresponding crystalline counterparts. Formation and evolution of crystalline phases during heat-treatment of the as-quenched ternary alloys up to liquid state were shown using in-situ XRD. Analysis of the morphology of the as-quenched and annealed Al-T-Si ribbons has been performed by transmission electron microscopy. [ABSTRACT FROM AUTHOR]

We constructed a unique heterointerface of crystalline Au nanoparticles and amorphous porous CoSnO 3 nanocubes for sensitive electrochemical detection of glucose. [Display omitted] • Au/CoSnO 3 was explored as a novel electrocatalyst for highly sensitive nonenzymatic detection of glucose. • It is the first time that CoSnO 3 is employed as electrocatalyst for glucose oxidation. • The formation of a unique amorphous/crystalline heterogeneous interface makes Au/CoSnO 3 exhibit remarkable catalytic performance for glucose detection. Au/CoSnO 3 was explored as a novel electrocatalyst for highly sensitive nonenzymatic detection of glucose. Au/CoSnO 3 was synthesized by a galvanic replacement strategy. The obtained nanomaterials were characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDS), X-ray diffractometry (XRD) and electrochemical techniques. The results display that a small amount of crystalline Au nanoparticles are decorated on the surface of amorphous porous CoSnO 3 nanocubes. The formation of such unique amorphous/crystalline heterogeneous interface makes Au/CoSnO 3 exhibit excellent electrocatalytic activity for the electrochemical oxidation of glucose. The sensor based on Au/CoSnO 3 can detect glucose with a wide linear detection range of 0.2 µM–0.11 mM, a high sensitivity of 2317.1 µA·mM−1·cm−2 and a low detection limit of 0.078 µM. This study demonstrates CoSnO 3 as an effective sensing material and also provides a way to improve electrocatalytic properties of nanomaterials through interfacial engineering. [ABSTRACT FROM AUTHOR]

The morphology of $$ \{ 10\overline{1} 2\} \left\langle {\overline{1} 011} \right\rangle $$ deformation twins formed in commercial purity titanium during an initial pass of equal-channel angular pressing was studied by transmission electron microscopy (TEM). The corresponding diffraction patterns show a symmetry line splitting of $$ (10\overline{1} 2) $$ twin boundaries (TB) which is related to the presence of interfacial defects. A simple modeling for the interaction between non-screw a-slip lattice dislocations (Burgers vector b = $$ \frac{1}{3}[\overline{1} \overline{1} 20] $$ ) and the $$ (10\overline{1} 2) $$ twin plane is used according to crystallographic geometry and vector conservation. The results show that dislocation dissociation into different Frank partial dislocations on the interfacial plane is more favorable than its transmission to the other side of the interface. The formation of the Frank partials at the TB can produce a small change in the TB misorientation angle and this is consistent with the symmetry line splitting of the $$ (10\overline{1} 2) $$ twin boundaries observed by TEM. [ABSTRACT FROM AUTHOR]

The structural properties of nanoscale Ag, La(OH), CuS (covellite), AgS (acanthite), and ZnO hollow spheres, massive Ag nanoparticles and In-Ag core-shell nanoparticles with outer diameters between 200 and 400 Å, were investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM), dynamic light scattering (DLS), and differential sedimentation (DS). Lognormal size distributions of single-crystalline (quasi)spherical nanoparticles are found in our samples by DLS, STEM, DS, and HRTEM. The lattice parameters of the nanomaterials are determined by XRD line-position analysis, while the volume-averaged size and the microstrain are derived by the average-size and strain approximation in the integral breadth method. A new expression is presented in this work to derive the real average outer diameter $$ \bar{D} $$ of hollow spherical particles. The good agreement between $$ \bar{D} $$ and the corresponding diameter determined by DLS in the case of Ag and La(OH) hollow spheres demonstrates the validity of the approach. The same expression is applied to derive the average wall thickness of CuS and AgS hollow spheres as well as for the Ag shell thickness of In-Ag core-shell nanoparticles. [ABSTRACT FROM AUTHOR]

A general and facile approach for tailoring the multicolor output and shapes of lanthanide-ion doped fluoride upconversion nanoparticles (UCNPs) within a given composition is presented. By adjusting the temperature and time in the thermolysis procedure, the color output and shapes of NaYF4:20%Yb, 2%Er UCNPs can be readily manipulated. The nanoparticles were characterized through the use of transmission electron microscopy (TEM), powder X-ray diffraction (XRD) and upconversion luminescence spectroscopy. It is shown that the relative intensities of green emissions gradually increased with the rise of temperature and prolongation of growth time under excitation of 980 nm, which resulted in multicolor output of NaYF4:20%Yb, 2%Er UCNPs. Simultaneously, the shapes for UCNPs can also be controlled. TEM images, estimated micro-stress by Williamson–Hall methodology and a series of control experiments and analyses reveal that crystallinity is mainly responsible for the multicolor output of UCNPs. Based on the above method, the tailoring of color output is also successfully realized in Ho3+and Tm3+ions. It is expected that this method may be used to tune the physical properties of other nanoparticles, and these multicolored UCNPs are promising for applications in multiplexed bioimaging, biodetection, display, other optical technologies, etc. [ABSTRACT FROM AUTHOR]

Abstract: A new photocatalyst, namely single-crystalline Bi5O7NO3 nanofibers, was prepared by a facile hydrothermal method in the presence of Triton X-100 and ammonia. Bi5O7NO3 possessing a crystalline sheet morphology could be dissolved and transformed into nanofibers by controlling the reaction time. Samples were characterized by X-ray diffraction, UV–vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and high resolution transmission electron microscopy. The Bi5O7NO3 nanofiber growth mechanism is discussed in detail. The band gap energy of the as-prepared Bi5O7NO3 photocatalyst was about 2.70–2.90eV. Results of first-principle density functional theory calculations confirmed that Bi5O7NO3 had a narrow band gap. They revealed that the conduction band bottom was predominantly composed of Bi 6s, Bi 6p, N 2p and O 2p orbitals, while the valence band (VB) top primarily consisted of Bi 6p, Bi 6s and O 2p orbitals. The as-obtained Bi5O7NO3 nanofibers showed good photocatalytic activity and stability for the degradation of Rhodamine B (RhB) under visible light irradiation, which may be ascribed to the highly mobile conduction band (CB) and VB charge carriers. [ABSTRACT FROM AUTHOR]

Deformation-induced crystallization is correlated with thermal-induced crystallization in alloys with different compositions in a single amorphous alloy system. In Al87Y6Ni5Co2 and Al85Y8Ni5Co2 alloys, which undergo primary crystallization during heating, deformation-induced crystallization of fcc-Al has been observed. In Al83Y10Ni5Co2 alloy, which undergoes eutectic-like crystallization, no deformation-induced crystallization was observed. These observations can be explained by the presence or absence of quenched-in nuclei and the work required for the creation of an amorphous/crystalline interface under compressive stress. [ABSTRACT FROM AUTHOR]

Abstract: We report on tension–compression cyclic loading of single-slip oriented silicon single crystals between 1073 and 1173K. In the temperature and strain rate domains investigated, dislocation glide is still controlled by lattice friction. Along cycling, a maximum stress is attained through two hardening stages, a logarithmic, followed by a linear one. At variance to what is observed in metals (fcc and bcc), the maximum stress decreases with increasing strain amplitude. This effect may be a consequence of the combined strain localization and the strain-rate sensitivity of Si. The built-up dislocation structures, observed in transmission electron microscopy (TEM) show three basic types of arrangements. During the linear hardening, dislocations dipoles gather in corrugated walls, separated by zones of lower density. Once the maximum stress is attained, strain localizes in walls and channels that retain the initial chevron shape, but in which the walls are much thinner. Well-characterized “ladder-structure” currently observed in persistent slip-bands are here very rare. Characteristic lengths of the observed patterns are given and briefly discussed in the light of current theories of cyclic deformation. For this purpose, convergent-beam electron diffraction patterns were taken across a channel to account for potential internal-stress effects. [Copyright &y& Elsevier]

Polycrystalline silicon obtained by the crystallization of thin amorphous silicon films has been an important material for microelectronics technology during the last decades. Many properties are improved in crystallized amorphous silicon compared to the as-deposited polysilicon such as larger grain size, smoother surface, and higher-carrier mobility. In this work, the crystallization of amorphous silicon is investigated by combining transmission electron microscopy (TEM) observations and molecular dynamics calculations. TEM observations on a series of specimens have shown that the majority of the silicon grains are oriented with a $$ {\left\langle {110} \right\rangle} $$ zone axis normal to the surface. In order to understand the crystallization mechanism molecular dynamic simulations were performed. It is found that the $$ {\left\langle {110} \right\rangle} $$ c/amorphous interface exhibits the lowest reduced interfacial energy density while the $$ {\left\langle {111} \right\rangle} $$ c/amorphous has the lowest reduced energy differences per unit interfacial area. The most energetically unfavorable interface is $$ {\left\langle {001} \right\rangle} $$ c/amorphous. [ABSTRACT FROM AUTHOR]

The structure of a < 110 > 90° grain boundary in Au is investigated using high-resolution transmission electron microscopy (HRTEM) and atomistic simulation. It consists of coherent segments, exhibiting the extended 9R configuration described by Medlin et al . 10, with superimposed line defects to accommodate the coherency strain. Two types of defects are observed, crystal dislocations and disconnections, where the latter exhibit step nature in addition to dislocation character. Both types of defect are identified by HRTEM in combination with circuit mapping, and their parameters are shown to be consistent with the topological theory of interfacial defects 7. Moreover, the misfit-relieving function of observed defect arrays, their influence on interface orientation and the relative rotation of the adjacent crystals is elucidated. During observation, defect decomposition is observed in a manner which conserves Burgers vector and step height. One of the decomposition products is glissile, consistent with the ‘glide/climb’ rules for interfacial defects. This glissile motion is also found by atomistic simulation of the disconnection when an applied strain is imposed. The γ -surface for the interface is calculated and shows that no alternative boundary structure is stable, confirming, consistent with experimental observation, that defects separating different configurations are not feasible. [ABSTRACT FROM AUTHOR]

Abstract: . A crystalline interface is often covered by a dense network of linear defects with a (pseudo) biperiodic geometry. The elastic field of this network is calculated by thinking the interface as paved by adjacent Somigliana dislocations. The analysis of a portion of an erratic zigzag line of a (001)Si low angle twist boundary, observed in two-beam transmission electron microscopy, is given as an example. To cite this article: A. Boussaid et al., C. R. Physique 6 (2005). [Copyright &y& Elsevier]

Cubic boron nitride (c-BN) nanocrystals have been synthesized by pulsed laser induced liquid–solid interfacial reaction. It is shown that the diameters of the prepared quasi-spherical c-BN nanocrystals vary from 30 to 80 nm via transmission electron microscopy (TEM). The 2θ values of the X-ray diffraction (XRD) peaks of the resultant c-BN nanocrystals are 43.16°, 74.16°, 90.08° and 136.1°, respectively, corresponding to the (1 1 1), (2 2 0), (3 1 1) and (3 3 1) crystalline planes of a c-BN phase. Fourier transform infrared (FTIR) spectroscopy has also been used to characterize the structure of boron nitride. The formation of c-BN nanocrystals upon pulsed laser ablation at the liquid–solid interface is discussed in detail. [Copyright &y& Elsevier]

A method is presented for quantitatively assessing the strength of interatomic bonding forces across interfaces between two dissimilar crystalline materials. At such interfaces, the mismatch of corresponding lattice parameters gives rise to a periodic pattern of linear regions of poor match, denoted as 'misfit dislocations'. The atom displacements that occur in these regions constitute an 'image' of the bonding forces across the interface. By fitting a model of the displacement field to experimentally determined atom positions at misfit dislocation cores, therefore, it should be possible to assess the mechanical strength of the interatomic bonds across the interface. The feasibility of this approach is demonstrated for the cubeon-cube interface between a SrTiO[sub 3](001) substrate and an epitaxial layer of SrZrO3. The atom positions at the misfit dislocations in this interface were determined with small error limits (0.03 nm) by quantitative high-resolution transmission electron microscopy. By fitting a continuum model describing the displacement field of misfit dislocations as a function of elasticity parameters of the interfacial bond layer and the two juxtaposed crystals, it is possible to determine the shear stiffness of the interatomic bonds across this interface quantitatively and with well-defined error limits (30%). Moreover, the analysis enables determining Poisson's ratio and the shear modulus of epitaxial layers, in this case SrZrO[sub 3]. The method introduced here has a broad range of applications. [ABSTRACT FROM AUTHOR]

We introduce a new method to determine the ‘lattice offset’ or ‘rigid-body shift’ between two crystals forming an interface. Our method relies on quantitative evaluation of high-resolution transmission electron microscopy images. Employing the (001)-orientated interface between Al and MgAl2O4 in parallel orientation as a model system we demonstrate that we can assess the interface lattice offset with a precision in the picometre range. [ABSTRACT FROM AUTHOR]

Ion beam mixing of Fe/Si bilayers, induced by 100 keV 40Arions at room temperature was investigated. Rutherford backscattering spectroscopy (RBS), atomic force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were applied for structural characterization. The main focus of this study was on the influence of the substrate structure on interface mixing. The influence of the substrate structure is due to the two classes of irradiated bilayers, Fe thin films deposited on crystalline or pre-amorphized Si substrates. An about 76% higher efficiency of atomic transport across the pre-amorphized Fe/a-Si interface as compared to that of Fe/c-Si bilayers was observed. [ABSTRACT FROM AUTHOR]

• The crystalline and amorphous interface of FeS 2 and polyaniline is constructed. • The S element is doped into the PANI by forming C S covalent bond. • The crystalline and amorphous interface improves the electrocatalytic activity. • The potential is 1.49 V at 10 mA cm−2 for oxygen evolution in 1 M KOH solution. We report a facile strategy to synthesize the FeS 2 /polyaniline/exfoliated graphene (FeS 2 /PANI /EG) with the formation of crystalline and amorphous interface for enhanced electrocatalytic activity. The PANI layer consists of nanowires roughly 100 nm in diameters and exhibits randomly distributed porous structure and the diameters of FeS 2 distributed from 5 nm to 15 nm. The transmission electron microscopy image indicates the successful construction of crystalline and amorphous interface between FeS 2 and PANI. In addition, the S element is doped into the PANI by forming C S covalent bond. Thus, the prepared FeS 2 /PANI/EG film shows excellent catalytic activity with the potential of 1.49 V at 10 mA cm−2 for oxygen evolution reaction in 1 M KOH solution, comparing with the 1.59 V and 1.65 V for FeS 2 /EG and PANI/EG, respectively. [ABSTRACT FROM AUTHOR]

4H-polytype AlN has been grown on a 4H-SiC substrate with the (1120) face via plasma-assisted molecular-beam epitaxy. The microscopic structure of the AlN/4H-SiC interface was examined using high-resolution transmission electron microscopy, and the polytype replication of the 4H structure from the 4H-SiC(1120) substrate was evidently confirmed. The x-ray rocking curve of (1120) diffraction for the single crystalline 4H-AlN epilayer exhibited a very small linewidth of 90 arc sec, suggesting noticeably small tilting around the [1120] direction. The excellent crystalline quality is probably owing to the polytype matching between the 4H-AlN epilayer and the 4H-SiC substrate, which resulted in remarkable reduction of defects at the interface. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Examines the crystalline structure near the substrate interface for aluminum films grown on sapphire substrates. Application of metalorganic chemical vapor deposition technique in thin film productions; Role of transmission electron lattice images in depicting interface coherence; Identification of dislocation defect structure of the substrate interface epilayer.

Determines the atomic structure of the B-type gamma-FeSi[sub 2]//Si(111) interfaces by high-resolution transmission electron microscopy. Combination of dynamical calculations of the image contrast in the study; Agreement of one interface model with observations; Attachment of Fe atoms to the substrate silicon atoms.

Investigates the Ag/Bi-Sr-Ca-Cu-O (BSCCO) interface in Ag-clad bi-2212 tapes by high-resolution transmission electron microscopy. Absence of nonsuperconducting second phases from the interface; Observation of a one-half-unit-cell-thick layer of the Bi-2201 phase; Presence of texturing of the (001) planes for the BSCCO parallel to the Ag.

An 11-MV arsenic beam was used to amorphize approximately 3.9 μm of GaAs surface layer at liquid nitrogen temperature. It was found that apparently amorphous gallium arsenide can be reconverted to single crystal by subsequent implantation at higher temperature. The recrystallization by the ion beam proceeded simultaneously from the amorphous surface and the deep amorphous/crystalline interface. Growth of dendrites and/or microtwins occurred at the recrystallizing interfaces. From the comparison of the nuclear stopping curve with the damage distribution in cross-sectional transmission electron micrograph, the threshold value for converting crystalline GaAs into amorphous GaAs was measured to be between 2-5×1020 keV cm-3. [ABSTRACT FROM AUTHOR]

This work describes, using mainly transmission electron microscopy as an investigation tool, the nature and behaviour of the crystalline defects which are present in (11-22) semipolar GaN films grown epitaxially on patterned r-sapphire substrates using a 3 step growth process. The microstructure at these different growth stages is described. The independent 3D-crystallites nucleated on the substrate surface contain threading dislocations resulting from the epitaxy on c-sapphire facets and basal stacking faults (BSFs), mainly in the  −c-wings. These defects are concentrated in a few hundred nanometre wide stripe-like regions emerging on the top facet of the islands. By a careful choice of the growth conditions, these defective regions may be overgrown by defect-free material, blocking their propagation towards the coalesced surface. However, when the 3D crystals coalesce, new dislocations together with very few BSFs are created at the coalescence boundaries. These coalescence defects propagate to the surface of the films in (0001) planes. In summary, the control of the nucleation and propagation of the crystalline defects allows obtaining large area semipolar films with very low defect densities: 7   ×   107 cm−2 for TDs and 70 cm−1 for BSFs. [ABSTRACT FROM AUTHOR]