Investigation of PbTiO3 crystal lattice defects by transmission electron microscopy

The investigation of PbTiO₃ single crystal structure was carried out by the method of transmission electron microscopy (TEM). It is shown that the following types of defects are observed: ferroelectric 90°-and 180°-domain boundaries, dislocations and their complexes, and planar defects.     

Investigation of crystal lattice defects of PbZrO3 single crystals by transmission electron microscopy

The investigation of PbZrO₃ single crystal structure was carried out by the method of transmission electron microscopy (TEM). It is shown that extended planar defects, slip lines, twins, and morié patterns are observed in PbZrO₃.     

Dislocations in silicon observed by high-voltage,high-resolution electron microscopy

Dislocations in deformed silicon crystals have been studied by high-resolution electron microscopy with the axial illumination along the [110] direction using a 1 MV electron microscope. Extended 60 dislocations, Z-shape faulted dipoles and stacking fault tetrahedra were observed in atomic level. The results demonstrated the potentiality of highvoltage, high-resolution electron microscopy for the study of atomic configurations of structural defects.     

Investigation for ferroelectric domains by scanning electron microscopy

Examples for the direct observation of domain structures in ferroelectric crystals by means of scanning electron microscopy are given. The results for TGS and AFB crystals with direction of the polarization vector perpendicular to the observed surface are presented with respect to temperature changes, to domain enlargement under the influence of an external electric field and to the influence of X-ray- and γ-radiation on the domain formation.     

Characterization of defects in GaP and GaAsP graded heterojunctions by transmission electron microscopy

Misfit dislocations are observed in graded heterojunctions GaAs_1?xP_x by electron microscopy. Results are in agreement with previous work concerning the nature of the dislocations (Lomer and 60° dislocations) and their density dependence on the phosphorus gradient. The discussion concerns the formation of Lomer dislocations and the possibility of reducing the density of inclined dislocations which reach the surface of the epitaxial layer. GaP substrates, S-doped, are examined by transmission electron microscopy. Numerous defects such as Frank loops, perfect loops, helical dislocations and precipitates are observed. A GaP homoepitaxial layer realized on this substrate is free from these defects but exhibits stacking faults. A zinc diffusion does not produce additional defect but a 1000 Å thick amorphous layer is observed a at the surface.     

Transmission electron microscopy investigation of B27 martensitic phase in polycrystalline YCu intermetallic compound

Polycrystalline YCu specimens with a CsCl‐type B2 structure made by induction melting were investigated by transmission electron microscopy (TEM). TEM studies show that an orthorhombic YCu B27 martensite with FeB‐type structure having lattice parameters a = 0.71 nm, b = 0.45 nm and c = 0.54 nm forms during deformation at ambient temperature. (101) twins are observed in the YCu B27 phase. The orientation relationship of B27 with B2 matrix is (001)[1 0]_B27 ‖ (112)[1 0]_B2. Effects of B27 phase formation on the ductility of YCu alloy are discussed. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of generated defects during plastic deformation on electron properties of silicon

Conductivity, photoconductivity and SDP of n-type silicon deformed and annealed under different thermal conditions were investigated. The conductivity was found to be dependent on the temperature of deformation and additional annealing. Recombination in deformed samples is fully controlled by paramagnetic centers localized within the charge space region around the dislocations.     

Investigation of the structure of nanocrystalline refractory oxides by X-ray diffraction,electron microscopy,and atomic force microscopy

The structures of nanocrystalline fibrous powders of refractory oxides have been investigated by different methods: determination of coherent-scattering regions, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic-force microscopy (AFM). The sizes of nanograins of different crystalline phases of refractory metal oxides have been determined during the formation of these nanograins and the dynamics of their growth during heat treatment in the temperature range 600–1600°C has been studied. The data on the structure of nanocrystalline refractory oxide powders, obtained by different methods, are in good agreement. According to the data on coherent-scattering regions, the sizes of the ZrO₂ (Y₂O₃) and Al₂O₃ grains formed are in the range 4–6 nm, and the particle sizes determined according to the TEM and AFM data are in the ranges 5–7 and 2–10 nm, respectively. SEM analysis made it possible to investigate the dynamics of nanoparticle growth at temperatures above 1000°C and establish the limiting temperatures of their consolidation in fibers.

     

Characterization of crystal defects in mixed tabular silver halide grains by conventional transmission electron microscopy and X-ray diffractometry

Tabular silver bromide grains with iodide uniformly mixed in the shell were investigated with conventional transmission electron microscopy. The shell region was found to contain a large number of stacking faults parallel with the {11 } edges and in some cases edge dislocations with a Burgers vector of type. An atomic model for the formation of the stacking faults during the growth is presented.     

Study of structural order in porphyrin-fullerene dyad ZnDHD6ee monolayers by electron diffraction and atomic force microscopy

The structure of porphyrin-fullerene dyad ZnDHD6ee monolayers formed on the surface of aqueous subphase in a Langmuir trough and transferred onto solid substrates has been studied. The data obtained are interpreted using simulation of the structure of isolated molecules and their packing in monolayer and modeling of diffraction patterns from molecular aggregates having different sizes and degrees of order. Experiments on the formation of condensed ZnDHD6ee monolayers are described. The structure of these monolayers on a water surface is analyzed using π-A isotherms. The structure of the monolayers transferred onto solid substrates is investigated by electron diffraction and atomic force microscopy. The unit-cell parameters of two-dimensional domains, which are characteristic of molecular packing in monolayers and deposited films, are determined. Domains are found to be organized into a texture (the molecular axes are oriented by the [001] direction perpendicular to the substrate). The monolayers contain a limited number of small 3D domains.     

Transmission electron microscopy study of defects in AlN crystals with rough and smooth surface grains

Defects present in (0 0 0 1) textured polycrystalline AlN grown by the sublimation–recombination method were analyzed using transmission electron microscopy (TEM) methods. Grains in the polycrystalline boule had either a smooth or a rough surface. The rough surface grains had mainly edge dislocations, whereas the smooth surface grains had some sub-grain boundaries and were mostly free of dislocations. Dislocations at the grain boundaries were pinned and could not be annihilated.     

On the characterization of individual defects in silicon by EBIC

EBIC recombination-contrast of defects is mainly caused by impurity atmospheres surrounding them. The contrasts for geometrically similar defects in samples having different diffusion lengths L > 100 μm are in proportion to the defect strengths .     

EPR Studies of defects in silicon

Electron and neutron irradiated, plastically deformed silicon has been studied by EPR. Irradiation resulted in a strong decrease of the EPR spectra produced by the deformation and in the appearance of a new EPR center at dislocations. Thermal annealing lead to a reestablishment of the formerly present dislocation spectra. As most probable explanation is proposed a change of the dislocation strain field by irradiation induced point defect iclusters. – EPR investigations of iron in boron doped Si demonstrated the pairing of all nterstitial iron in FeB pairs during room temperature storage. Thermal treatment at temperatures higher than 100°C lead to the reappearance of Fe. Therefore the time limiting factor for the annealing of FeB pairs should be the precipitation of interstitial iron.     

X-ray and electron microscopy studies of arsenium implanted silicon crystals after a pulsed laser annealing

The structural changes obtained due to laser annealing in the surface layer of As-implanted silicon crystals were investigated by means of a triple crystal spectrometer. The rocking curves of implanted crystals do not show any changes compared with non-implanted crystals. It was caused by the large dose of ions which amorphized the surface layer. Laser annealing process influenced on the broadening of rocking curve. The comparative studies were carried out by using the HTEM technique. They showed that the laser annealing caused formation of quasi-mosaic structure, planar defects and dislocation clusters. These defected structure and local strains influence on the broadening of rocking curves.     

Pressure assisted evolution of defects in silicon

The effect of enhanced hydrostatic pressure following heat treatment on the evolution of point defects in neutron‐irradiated Czochralski‐grown silicon is investigated using infrared spectroscopy. The behavior of oxygen‐related defects, particularly of the VO and the VO₂ centers, is mainly studied using samples subjected to heat treatment under hydrostatic pressure. It is observed that (1) pressure accelerates the annealing process of the VO defects and enhances the growth of the VO₂ complexes and (2) the VO₂ concentration is larger than expected from the corresponding decay of the VO defects. The faster decay of the VO defects is attributed to a pressure‐induced decrease of their migration energy. The larger VO₂ concentration is also discussed. One possible explanation is that pressure stimulates an additional mechanism for the formation of the VO₂ defects, which involves the reaction of oxygen dimers with vacancies. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Study of the structural quality of heteroepitaxial silicon-on-sapphire structures by high-resolution X-ray diffraction,X-ray reflectivity,and electron microscopy

Heteroepitaxial silicon-on-sapphire (SOS) structures have been studied by high-resolution X-ray diffraction, X-ray reflectivity, electron microscopy, and electron diffraction. These methods yielded a large amount of complementary data on the defect structure of both the sapphire substrate and the silicon film, including integral and local (at the atomic-resolution level) information about the substrate, film, and sapphire-silicon interface.     

X-ray diffraction study of defects in zinc-diffusion-doped silicon

Samples of CZ n-Si〈Zn〉(111) are prepared by high-temperature zinc-diffusion annealing followed by quenching and are studied by X-ray diffraction. The silicon contains an initial phosphorus impurity and zinc-compensating admixture at concentrations N _P = 1.5 × 10¹⁴ cm^?3 and N _Zn = 1 × 10¹⁴ cm^?3; i.e., the relation N _P/2 < N _Zn < N _P is fulfilled. Microdefects are studied by double- and triple-crystal X-ray diffraction in the dispersion free modes (n, ?n) and (n, ?n, +n). The samples are found to contain microdefects with two characteristic sizes (average sizes of about 1 μm and 70 nm). The interplanar distance in the near-surface layer with a thickness of 0.1 μm is smaller than this parameter in the remaining matrix, the difference being equal to d ₀ Δd/d ₀ ≈ 2 × 10^?5. This layer contains mainly vacancy-type microdefects. The angle between the reflecting planes and the local surface relief is Δψ = (7 ± 1) arcmin.     

Characterization of silicon layers epitaxially grown on metallurgical-grade polycrystalline substrates

The structural and electrical properties of silicon layers epitaxially grown on metallurgical-grade polycrystalline silicon substrates are examined to clarify the effect of grain boundaries, crystal defects and impurities in the substrates. Chemical etching of the epitaxial layer reveals that all the grain boundaries continue from the substrate into the epitaxial layer, whereas lines of high density etch pits do not always continue. The polycrystalline thin film solar cells are fabricated on the metallurgical-grade silicon substrates by successive deposition of p and n⁺ layers. These cells show short circuit current densities around 70% of that of the conventional single crystal cell. This reduction of the short circuit current is caused mainly by the short minority carrier diffusion length in the grains probably due to impurities involved in the epitaxial layers. The origins of such impurities are discussed by considering autodoping and solid-state diffusion from the substrate during growth of epitaxial layers.