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Abstract Two thickness measurement methods using an electron energy loss spectroscopy (EELS) and 10a convergent beam electron diffraction (CBED) were compared in an Fe-18Mn-0.7C alloy. The thin foil specimen was firstly tilted to satisfy 10a two-beam condition. Low loss spectra of EELS and CBED patterns were acquired in scanning transmission electron microscopy (STEM) and TEM-CBED modes under the two-beam condition. The log-ratio method was used for measuring the thin foil thickness. Kossel-Möllenstedt (K-M) fringe of the 13 1 ¯ $$ \mathbf{13}\overline{\mathbf{1}} $$ diffracted disk of austenite was analyzed to evaluate the thickness. The results prove the good coherency between both methods in the thickness range of 72 ~ 113 nm with a difference of less than 5%.

A local structure analysis method based on convergent‐beam electron diffraction (CBED) has been used for refining isotropic atomic displacement parameters and five low‐order structure factors with sin gθ/λ ≤ 0.28 Å−1 of potassium tantalate (KTaO3). Comparison between structure factors determined from CBED patterns taken at the zone‐axis (ZA) and Bragg‐excited conditions is made in order to discuss their precision and sensitivities. Bragg‐excited CBED patterns showed higher precision in the refinement of structure factors than ZA patterns. Consistency between higher precision and sensitivity of the Bragg‐excited CBED patterns has been found only for structure factors of the outer zeroth‐order Laue‐zone reflections with larger reciprocal‐lattice vectors. Correlation coefficients among the refined structure factors in the refinement of Bragg‐excited patterns are smaller than those of the ZA ones. Such smaller correlation coefficients lead to higher precision in the refinement of structure factors. [ABSTRACT FROM AUTHOR]

The digital large‐angle convergent‐beam electron diffraction (D‐LACBED) technique is applied to Ca3Mn2O7 for a range of temperatures. Bloch‐wave simulations are used to examine the effects that changes in different parameters have on the intensity in D‐LACBED patterns, and atomic coordinates, thermal atomic displacement parameters and apparent occupancy are refined to achieve a good fit between simulation and experiment. The sensitivity of the technique to subtle changes in structure is demonstrated. Refined structures are in good agreement with previous determinations of Ca3Mn2O7 and show the decay of anti‐phase oxygen octahedral tilts perpendicular to the c axis of the A21am unit cell with increasing temperature, as well as the robustness of oxygen octahedral tilts about the c axis up to ∼400°C. The technique samples only the zero‐order Laue zone and is therefore insensitive to atom displacements along the electron‐beam direction. For this reason it is not possible to distinguish between in‐phase and anti‐phase oxygen octahedral tilting about the c axis using the [110] data collected in this study. [ABSTRACT FROM AUTHOR]

The digital large‐angle convergent‐beam electron diffraction (D‐LACBED) technique is applied to Ca3Mn2O7 for a range of temperatures. Bloch‐wave simulations are used to examine the effects that changes in different parameters have on the intensity in D‐LACBED patterns, and atomic coordinates, thermal atomic displacement parameters and apparent occupancy are refined to achieve a good fit between simulation and experiment. The sensitivity of the technique to subtle changes in structure is demonstrated. Refined structures are in good agreement with previous determinations of Ca3Mn2O7 and show the decay of anti‐phase oxygen octahedral tilts perpendicular to the c axis of the A21am unit cell with increasing temperature, as well as the robustness of oxygen octahedral tilts about the c axis up to ∼400°C. The technique samples only the zero‐order Laue zone and is therefore insensitive to atom displacements along the electron‐beam direction. For this reason it is not possible to distinguish between in‐phase and anti‐phase oxygen octahedral tilting about the c axis using the [110] data collected in this study. [ABSTRACT FROM AUTHOR]

Position averaged convergent beam electron diffraction PACBED in scanning transmission electron microscopy is shown to be capable of determining the direction of ferroelectric polarity at the nanoscale. We show that PACBED patterns of ferroelectric materials such as PbTiO3 and BaTiO3 are sensitive to both unit cell distortion and the absolute direction of polarity within the unit cell. It is shown that the polarity can be determined even in cases where real-space high-resolution transmission electron microscopy would not be capable of resolving the atomic displacements. The method is applied to determine the direction of polarization in an epitaxial BaTiO3 film.

Two thickness measurement methods using an electron energy loss spectroscopy (EELS) and 10a convergent beam electron diffraction (CBED) were compared in an Fe-18Mn-0.7C alloy. The thin foil specimen was firstly tilted to satisfy 10a two-beam condition. Low loss spectra of EELS and CBED patterns were acquired in scanning transmission electron microscopy (STEM) and TEM-CBED modes under the two-beam condition. The log-ratio method was used for measuring the thin foil thickness. Kossel-Möllenstedt (K-M) fringe of the 13 1 ¯ diffracted disk of austenite was analyzed to evaluate the thickness. The results prove the good coherency between both methods in the thickness range of 72 ~ 113 nm with a difference of less than 5%. [ABSTRACT FROM AUTHOR]

Convergent beam electron diffraction (CBED) in transmission electron microscopy (TEM) was applied to determine local carbon concentrations in low‐carbon transformation‐induced plasticity (TRIP) steels. High‐order Laue‐zone (HOLZ) lines were experimentally obtained for comparison with simulation results. A new procedure for calculating carbon content is thus proposed. Retained austenite (RA) is classified into three types by morphology; the relationship between the carbon content and the corresponding RA morphology is discussed based on CBED results. Furthermore, results of X‐Ray diffractometry measurements are also used for comparison. CBED was applied to determine the carbon contents in TRIP steels.Experimental HOLZ lines were compared with simulated results; a related methodology of calculating carbon concentration was developed.Carbon was found to be inhomogeneously distributed. [ABSTRACT FROM AUTHOR]

A new method to retrieve the local lattice parameters and rotations in a crystal from off-axis convergent beam electron diffraction (CBED) patterns is presented and validated using Bloch wave dynamical simulations. The originality of the method is to use both the diffracted and transmitted beams and to use kinematical approximations in the fitting algorithm. The study is based on the deformation gradient tensor F which includes rotation and strain. Working on simulated images it is shown that (i) from a single direction of observation, seven parameters out of the nine parameters of F can be determined with an accuracy of 3×10 −4 for the normal strain parameters ε xx , ε yy , and ε zz , (ii) the unit cell volume can only be retrieved if the diffracted and transmitted beams are both included in the fitting and (iii) all the nine parameters of F can be determined by combining two directions of observation separated by about 20°. [ABSTRACT FROM AUTHOR]

While the computational complexity of calculation of the projected potential in the multislice algorithm through reciprocal space scales quadratically with the number of atoms A per slice, a pure real-space calculation scales linearly with A . A hybrid strategy is introduced that has a theoretical complexity of O ( A log A ) , but that, when measured, outperforms both the reciprocal-space and the real-space approach by approximately an order in A and a large factor, respectively. This strategy is implemented in a new program, dubbed forward dynamical electron scattering (FDES), which simulates high resolution transmission electron microscopy images, diffraction patterns and convergent beam electron diffraction patterns. FDES attains a further increase in speed by running on a graphics processing unit and is made available to the community as open software. [ABSTRACT FROM AUTHOR]

An experimental method to measure the strain through the thickness of a crystal is demonstrated. This enables the full three-dimensional stress–strain state of a crystal at the nanoscale to be determined taking the current practice from two-dimensional strain state determination. Knowing the 3D strain state is desired by crystal growers in order to improve their crystal's quality. This method involves combining electron diffraction with electron interferometry in a transmission electron microscope. The electron diffraction uses a split higher order Laue zone (HOLZ) line and the electron interferometry uses an electron biprism. [ABSTRACT FROM AUTHOR]

An automated processing of convergent beam electron diffraction (CBED) patterns is presented. The proposed methods are used in an automated tool for estimating the thickness of transmission electron microscopy (TEM) samples by matching an experimental zone-axis CBED pattern with a series of patterns simulated for known thicknesses. The proposed tool detects CBED disks, localizes a pattern in detected disks and unifies the coordinate system of the experimental pattern with the simulated one. The experimental pattern is then compared disk-by-disk with a series of simulated patterns each corresponding to different known thicknesses. The thickness of the most similar simulated pattern is then taken as the thickness estimate. The tool was tested on [0 1 1] Si, [0 1 0] α -Ti and [0 1 1] α -Ti samples prepared using different techniques. Results of the presented approach were compared with thickness estimates based on analysis of CBED patterns in two beam conditions. The mean difference between these two methods was 4.1% for the FIB-prepared silicon samples, 5.2% for the electro-chemically polished titanium and 7.9% for Ar + ion-polished titanium. The proposed techniques can also be employed in other established CBED analyses. Apart from the thickness estimation, it can potentially be used to quantify lattice deformation, structure factors, symmetry, defects or extinction distance. [ABSTRACT FROM AUTHOR]

Convergent-beam electron diffraction (CBED) recorded using nanometre-sized probes, in principle, can detect the highest symmetry in a crystal. However, symmetry reduction may occur by overlapping crystal domains along the beam direction. Thus, delineating the relationship between the recorded and the crystal symmetry is important for studying crystals with complex nanodomains. This paper reports a study of the averaged local symmetry of 71°/109° rhombohedral (R), 90° tetragonal (T) and 180° monoclinic (M) nanodomain structures. The averaged symmetry of nanodomain structures is investigated by CBED simulations using the multislice method. The simulation results show that the 71°-R, 109°-R and 90°-T nanodomain structures partially mimic the monoclinic symmetries of Cm and Pm that have been proposed by the adaptive phase model. This study is also compared to the reported experimental CBED patterns recorded from PMN-31%PT. [ABSTRACT FROM AUTHOR]

Abstract: The yield strength of different pipeline steel grades, rolled under four different conditions, was correlated with calculated strengthening contributions. Slabs with the same composition were rolled under identical roughing conditions but varied finish rolling temperature (FRT). Two cooling routes, consisting of accelerated water cooling condition (ACC) followed by slow cooling in an oven to simulate coiling and air cooling were applied after the last rolling pass. The microstructures obtained after each thermo mechanical controlled process (TMCP) schedule, were characterized using Transmission Electron Microscopy (TEM), Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Electron backscatter diffraction (EBSD). The mechanical properties of the plates were determined by means of tensile tests and Charpy V-notch impact test. It was confirmed that a combination of fast cooling rate and low finish rolling temperature produces higher strength than the slow cooling rate and high finish rolling temperature. Contributions to the strengthening arising from the various microstructural features like solid solution strengthening, grain size, dislocation density and precipitation hardening, were analyzed using Taylor, Hall–Petch and Ashby–Orowan approaches. The root of the sum of the squares method was applied to link the experimental with the model-predicted strength. It is believed that this approach provides a better understanding of the effect of TMCP parameters on the microstructure and strengthening mechanisms in pipeline steels. [Copyright &y& Elsevier]

A century has passed since Bragg solved the first atomic structure using diffraction. As with this first structure, all atomic structures to date have been deduced from the measurement of many diffracted intensities using iterative and statistical methods. We show that centrosymmetric atomic structures can be determined without the need to measure or even record a diffracted intensity. Instead, atomic structures can be determined directly and quickly from the observation of crystallographic phases in electron diffraction patterns. Furthermore, only a few phases are required to achieve high resolution. This represents a paradigm shift in structure determination methods, which we demonstrate with the moderately complex α-Al2O3. We show that the observation of just nine phases enables the location of all atoms with a resolution of better than 0.1 Å. This level of certainty previously required the measurement of thousands of diffracted intensities. [ABSTRACT FROM AUTHOR]

The advantages of convergent-beam electron diffraction for symmetry determination at the scale of a few nm are well known. In practice, the approach is often limited due to the restriction on the angular range of the electron beam imposed by the small Bragg angle for high-energy electron diffraction, i.e. a large convergence angle of the incident beam results in overlapping information in the diffraction pattern. Techniques have been generally available since the 1980s which overcome this restriction for individual diffracted beams, by making a compromise between illuminated area and beam convergence. Here a simple technique is described which overcomes all of these problems using computer control, giving electron diffraction data over a large angular range for many diffracted beams from the volume given by a focused electron beam (typically a few nm or less). The increase in the amount of information significantly improves the ease of interpretation and widens the applicability of the technique, particularly for thin materials or those with larger lattice parameters. [ABSTRACT FROM AUTHOR]

Nanoindentation experiments inside a transmission electron microscope are of much interest to characterize specific phenomena occuring in materials, like for instance dislocation movements or phase transformations. The key points of these experiments are (i) the sample preparation and the optimization of its geometry to obtain reliable results and (ii) the choice of the transmission electron microscope observation mode, which will condition the type of information which can be deduced from the experiment. In this paper, we will focus on these two key points in the case of nanoindentation of zirconia, which is a ceramic material well known to be sensitive to stress because it can undergo a phase transformation. In this case, the information sought is the stress localization at the nanometre scale and in real time. As far as the sample preparation is concerned, one major drawback of nanoindentation inside a transmission electron microscope is indeed a possible bending of the sample occurring during compression, which is detrimental to the experiment interpretation (the stress is not uniaxial anymore). In this paper, several sample preparation techniques have been used and compared to optimize the geometry of the sample to avoid bending. The results obtained on sample preparation can be useful for the preparation of ceramics samples but can also give interesting clues and experimental approaches to optimize the preparation of other kinds of materials. The second part of this paper is devoted to the second key point, which is the determination of the stress localization associated to the deformation phenomena observed by nanoindentation experiments. In this paper, the use of convergent beam electron diffraction has been investigated and this technique could have been successfully coupled to nanoindentation experiments. Coupled nanoindentation experiments and convergent beam electron diffraction analyses have finally been applied to characterize the phase transformation of zirconia. [ABSTRACT FROM AUTHOR]

Abstract: The transformation of zirconia from its tetragonal to its monoclinic phase is an important feature of the zirconia system. First found to be an advantage due to its important toughening effect, it can also be very detrimental when it occurs in the framework of low-temperature degradation, particularly in the case of biomaterial applications. One way to avoid or to control this phase transformation is to understand how it initiates and more particularly the stress states that can trigger it. A new technique available inside a transmission electron microscope seems to be particularly well suited for that type of study: convergent beam electron diffraction, a well-known technique to reveal stresses, was coupled to in situ transmission electron microscopy mechanical nanoindentation. The experiments reveal the presence of sheared nanoregions at grain boundaries. These could act as embryos for tetragonal-to-monoclinic phase transformations. This is an important first step in the understanding of the earliest stage of zirconia phase transformation. [Copyright &y& Elsevier]

We trace the historical development of W. L. Bragg's `law' and the key experimental observation which made it possible using polychromatic radiation at a time when neither X-ray wavelengths nor cell constants were known. This led, through his phasing and solving large mineral structures (without use of a computer), to work on metals, proteins, bubble rafts and his X-ray microscope. The relationship of this to early X-ray microdiffraction is outlined, followed by a brief review of electron microdiffraction methods, where electron-probe sizes smaller than one unit cell can be formed with an interesting `failure' of Bragg's law. We end with a review of recent femtosecond X-ray `snapshot' diffraction from protein nanocrystals, using an X-ray laser which generates pulses so short that they terminate before radiation damage can commence, yet subsequently destroy the sample. In this way, using short pulses instead of freezing, the nexus between dose, resolution and crystal size has been broken, opening the way to time-resolved diffraction without damage for a stream of identical particles. [ABSTRACT FROM AUTHOR]

The polarity of rough and smooth grains in textured aluminum nitride boules were analyzed by transmission electron microscopy. Specifically, convergent beam electron diffraction method was applied to determine polarity. The grains corresponding to smooth and rough surfaces were identified as having Al and N polarities, respectively. Aluminum oxide (Al2O3) was observed to form at the grain boundaries. The oxide may precipitate due to the low mutual solubility between Al2O3 and AlN at the high crystal growth temperature (∼2000°C). Oxygen may be the cause of polarity inversion that leads to the formation of Al and N polar grains. [ABSTRACT FROM AUTHOR]

This article deals with the measurement of strain in semiconductor heterostructures from convergent beam electron diffraction patterns. In particular, three different algorithms in the field of (circular) pattern recognition are presented that are able to detect diffracted disc positions accurately, from which the strain in growth direction is calculated. Although the three approaches are very different as one is based on edge detection, one on rotational averages, and one on cross correlation with masks, it is found that identical strain profiles result for an InxGa1−xNyAs1−y/GaAs heterostructure consisting of five compressively and tensile strained layers. We achieve a precision of strain measurements of 7–9·10−4 and a spatial resolution of 0.5–0.7 nm over the whole width of the layer stack which was 350 nm. Being already very applicable to strain measurements in contemporary nanostructures, we additionally suggest future hardware and software designs optimized for fast and direct acquisition of strain distributions, motivated by the present studies. [ABSTRACT FROM PUBLISHER]

This study presents a comprehensively and systematically structural, chemical and magnetic characterization of ~9.5 nm virtually monodispersed nickel ferrite (NiFeO) nanoparticles prepared using a modified liquid-solid-solution (LSS) assisted hydrothermal method. Lattice-resolution scanning transmission electron microscope (STEM) and converged beam electron diffraction pattern (CBED) techniques are adapted to characterize the detailed spatial morphology and crystal structure of individual NiFeO particles at nano scale for the first time. It is found that each NiFeO nanoparticle is single crystal with an fcc structure. The morphology investigation reveals that the prepared NiFeO nanoparticles of which the surfaces are decorated by oleic acid are dispersed individually in hexane. The chemical composition of nickel ferrite nanoparticles is measured to be 1:2 atomic ratio of Ni:Fe, indicating a pure NiFeO composition. Magnetic measurements reveal that the as-synthesized nanocrystals displayed superparamagnetic behavior at room temperature and were ferromagnetic at 10 K. The nanoscale characterization and magnetic investigation of monodispersed NiFeO nanoparticles should be significant for its potential applications in the field of biomedicine and magnetic fluid using them as magnetic materials. [ABSTRACT FROM AUTHOR]

Abstract: The addition of rare earth (RE) elements to Mg alloys can result in weaker hot deformation and recrystallization textures than those present in conventional Mg alloys. Recent studies of hot-rolled Mg–Nd binary alloys suggest that the texture weakening is influenced by the presence of second-phase particles. In this follow-up study, these particles are characterized morphologically, chemically, and crystallographically using transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The particles were observed to have a faceted morphology, particularly in the richer concentrations investigated, a composition of approximately 25at.% Nd (a stoichiometry of Mg3Nd) and an ordered cubic crystal structure (m3m point group) with a lattice parameter of approximately a ≈10.9Å, which is distinct from that of the equilibrium Mg3Nd phase. [Copyright &y& Elsevier]

Abstract: Spray pyrolysis is one of the most cost-effective methods to prepare SnO2 films due to its ability to deposit large uniform area, low fabrication cost, simplicity and low deposition temperature. Conventionally, scanning electron microscopy (SEM) and X-Ray Diffraction (XRD) are routinely used to investigate microstructure and crystal structure of the SnO2 films. In the present study, the SnO2 films were deposited by spray pyrolysis at 300, 400 and 500°C and the microstructure of the 500°C film was further examined by using transmission electron microscopy (TEM) and convergent beam electron diffraction (CBED). It was found that large grain-size vertically-aligned columnar SnO2 grains were formed after a few layers of small grain-size randomly oriented SnO2 grains. Moreover, CBED showed the presence of SnO nanodefects that had not been reported before and could not be detected by SEM or XRD. [Copyright &y& Elsevier]

Abstract: We refine two low-order structure factors of the skutterudite CoSb3 using convergent beam electron diffraction. The relatively large unit cell of this material causes the disks to overlap and introduces a series of challenges in the refinement procedure. These challenges and future work-arounds are discussed. The refined structure factors F 200 and F 600 are compared to X-ray diffraction and density functional calculated values, the latter calculated using two different functionals. Both relaxed and experimental lattice parameters are tested to explicitly highlight the impact of the lattice geometry and atomic position on the structure factors. [Copyright &y& Elsevier]

Abstract: Strain in a bridge-shaped freestanding Si membrane (FSSM) induced by depositing an amorphous Si x N y layer was measured by convergent-beam electron diffraction (CBED). CBED results show that the strain magnitude depends negatively on the FSSM thickness. FEM is a supplement of the result of CBED due to the relaxation of TEM samples during fabricating. The FEM analysis results ascertain the strain property in three dimensions, and show that the strain magnitude depends negatively on the length of FSSM, and the magnitude of the compressive strain in FSSM increases as the position is closer to the upper Si/Si x N y interface. [ABSTRACT FROM AUTHOR]

Abstract: SiGe multi quantum well structures were investigated by convergent-beam electron diffraction (CBED) measurements. Detailed layer characterizations were performed by acquiring series of bright field CBED patterns in the form of a line scan across the nanostructures in scanning transmission electron microscopy (STEM) mode. From the higher order Laue zone (HOLZ) lines the local lattice parameters were deduced. The Ge concentration corresponding to these lattice parameters was determined by means of the elasticity theory. In this work it is shown that the lattice constants can be determined locally with an accuracy of about ±0.001 to ±0.003Å which leads to an accuracy of the corresponding Ge concentration of about 1–2%. The characteristics of the focused electron probe and its influence on the experimental data were used for an estimation of the spatial resolution of the CBED method. For comparison, experimental values regarding the spatial resolution were determined by investigating the abrupt interface between Si(111) and AlN(0001). [ABSTRACT FROM AUTHOR]

Convergent beam electron diffraction patterns of silicon from the gate channel region of a complementary metal-oxide-semiconductor transistor with recessed Si.82Ge.18 stressors were analysed using three zone axes: <230>, <340> and <670>. Values measured using these axes were compared with each other with regards to strain along the [ ] and the [001] directions. It was demonstrated that strain measurements made using all three axes showed reasonable agreement with each other: an increase in the [ ] compressive strain and a switch from compressive to tensile strain in the [001] with decreasing distance below the gate. It was also observed that the strain calculations using the <230> axis had the lowest uncertainty whereas the <670> axis allowed for measurements closest to the gate due to the improved lateral resolution at that tilt angle. [ABSTRACT FROM AUTHOR]

Abstract: This study deals with the uncertainty of the measurement of lattice parameters by CBED using the kinematic approximation. The analysis of a large number of diffraction patterns acquired on a silicon sample at 93K with a LaB6 TEM without energy filter shows the presence of both the systematic and the random parts of errors. It is established that random errors follow the normal statistical distribution and that the precision quantified by the relative standard deviation is about 3–4×10−4 for lattice parameter measurements made from single pattern. The error sources are analyzed, different ways of enhancement are reviewed, and a new approach is proposed. It is shown that both accuracy and precision can be simply improved by taking into account multiple patterns analysis for the determination of the actual voltage, the single lattice parameter “a” or the complete set of lattice parameters. The precision of about 1.5–2×10−4 can be reached using a minimum of three HOLZ line patterns for the single “a” parameter and about 5×10−4 for the complete set of lattice parameters using six diffraction patterns. The use of multiple patterns also allows overcoming the non-uniqueness of solution linked to the CBED studies. [Copyright &y& Elsevier]

Abstract: A finely focused angstrom-sized coherent electron probe produces a convergent beam electron diffraction pattern composed of overlapping orders of diffracted disks that sensitively depends on the probe position within the unit cell. By incoherently averaging these convergent beam electron diffraction patterns over many probe positions, a pattern develops that ceases to depend on lens aberrations and effective source size, but remains highly sensitive to specimen thickness, tilt, and polarity. Through a combination of experiment and simulation for a wide variety of materials, we demonstrate that these position averaged convergent beam electron diffraction patterns can be used to determine sample thicknesses (to better than 10%), specimen tilts (to better than 1mrad) and sample polarity for the same electron optical conditions and sample thicknesses as used in atomic resolution scanning transmission electron microscopy imaging. These measurements can be carried out by visual comparison without the need to apply pattern-matching algorithms. The influence of thermal diffuse scattering on patterns is investigated by comparing the frozen phonon and absorptive model calculations. We demonstrate that the absorptive model is appropriate for measuring thickness and other specimen parameters even for relatively thick samples (>50nm). [Copyright &y& Elsevier]

Abstract: Convergent Beam Electron Diffraction (CBED) experiments and simulations associated with Finite Element calculations were performed in order to measure strain and stress in a complex device such as periodic MOS transistors with a spatial resolution of about 2nm and a sensitivity that could reach 50MPa. A lamella of a thickness of about 475nm was extracted from the wafer with the transistors by Focus Ion Beam (FIB) and was observed in cross-section in a Transmission Electron Microscope (TEM). When approaching the transistors, the HOLZ lines of the CBED patterns acquired in the silicon substrate, become broader and broader. This HOLZ line broadening, which is due to the stress relaxation in the thin foil, was used to determine quantitatively the strain and stress in the lamella and then in the bulk device. We showed that this procedure could be applied to a complex device. Two parameters, the intrinsic material strains – or equivalently the intrinsic material stresses – in the nickel silicide (NiSi) and nitride (Si3N4) layers on the top of the transistors gate, were successfully fitted by trial and error, in the procedure. [Copyright &y& Elsevier]

We have developed the focused ion beam (FIB) fold-out technique, for transmission electron microscopy (TEM) sample preparation in which there is no fine polishing or dimpling, thus saving turnaround time. It does not require a nanomanipulator yet is still site specific. The sample wafer is cut to shape, polished down, and then placed in a FIB system. A tab containing the area of interest is created by ion milling and then "folded out" from the bulk sample. This method also allows a plan-view of the sample by removing material below the wafer's surface film or device near the polished edge. In the final step, the sample is thinned to electron transparency, ready to be analyzed in the TEM. With both a cross section and plan-view, our technique gives microscopists a powerful tool in analyzing multiple zone axes in one TEM session. The nature of the polished sample edge also includes the ability to sample many areas, allowing the user to examine a very large device or sample. More importantly, this technique could make multiple site-specific e-beam transparent specimens in one polished sample, which is difficult to do when prepared by other methods. [ABSTRACT FROM AUTHOR]

Zirconium alloys are currently used in nuclear power plants where they are susceptible to hydrogen pick-up. Hydride precipitation may occur when the hydrogen solubility limit is reached. Various Zr hydride phases, γ, δ and ℇ have been identified since the 1950s. Combining electron precession microdiffraction, electron energy loss spectroscopy and ab initio electronic calculations, a new Zr hydride named ζ has been identified and characterized. It belongs to the trigonal crystal system with space group P3 m1 and it is fully coherent with the αZr matrix. [ABSTRACT FROM AUTHOR]

Abstract: The structural variants and their coexistence across the antiferroelectric phase transition in Sr0.60Ca0.40TiO3 ceramic has been studied through transmission electron microscopy (TEM) at room temperature and ∼100°C. A clear evidence of the presence of superlattice reflections, corresponding to the cell doubling along the c-axis of Pbnm (or b-axis along Pnma), occurring during paraelectric to antiferroelectric transition, has been obtained through selected area electron diffraction, convergent beam electron diffraction and lattice-resolution imaging. Coexistence of the Pbnm and Pbcm phases at room temperature has been observed and attributed to the strain/disorder-induced broadening of the first-order antiferroelectric phase transition. Drastic changes in the domain structure during Pbnm to Pbcm transformation have been observed. This clearly indicates that the antiferrodistortive transition responsible for the occurrence of the antiferroelectric phase is of completely different origin and it is not just an additional follow-up of the already-existing ordering due to a − a − c + tilt schemes in the Pbnm domain. Thermal cycling studies on microstructural changes indicate some kind of memory mechanism, which retains the memory of the original a − a − c + tilt schemes in the Pbnm phase. This has been attributed to the symmetry conforming short-range order (SC-SRO) of the point defects. [Copyright &y& Elsevier]

Abstract: A detailed structural study employing electron diffraction in selected area (SAD) and convergent beam electron diffraction (CBED) modes, followed by Rietveld analysis of the powder X-ray diffraction (XRD) data, has been carried out to identify the correct space group and to investigate the possible phase coexistence in Sr0.70Ca0.30TiO3 (SCT30) ceramics. The occurrence of distinctly two types of wide-angle CBED patterns and the presence of mutually perpendicular A2 type GM-lines in the forbidden reflections do show the coexistence of Pnma phase and a new orthorhombic phase with space group P21212 in SCT30. The occurrence of P21212 orthorhombic phase in SCT30 appears to be a result of distortion in addition with the rigid tilt of BO 6 octahedra. It so appears that the possibility of occurrence of P21212 for distorted perovskite structures is yet to be theoretically investigated. [Copyright &y& Elsevier]

Abstract: This paper investigates the interfacial structure in hot-wall CVD TiN/κ–Al2O3 multilayer coatings using both HREM and DFT modeling. Two multilayers with different thicknesses of the TiN layers (50 and 600 nm) separating the κ–Al2O3 layers are analyzed. The general microstructure of the two multilayers is relatively similar. The TiN layer in the thicker TiN/κ–Al2O3 coating is thick enough to be several TiN grains high. This means that epitaxial columns, which are often found in the thinner TiN/κ–Al2O3 coatings, are not present. However, the orientation relationships at the TiN/κ–Al2O3 interfaces are the same in both multilayers. The HREM investigations show that κ–Al2O3 (001) planes can grow directly on flat (111) TiN faces, without any other phases or detectable amounts of impurities, such as sulphur, present. Where the TiN layers are more curved, γ–Al2O3 can be grown, at least partly stabilized by the cube-on-cube orientation relationship between γ–Al2O3 and the underlying TiN. The DFT calculations show very similar adsorption strengths for an O monolayer positioned on Ti-terminated TiC(111) and TiN(111) surfaces, with preferred adsorption in the fcc site. O adsorption on N-terminated TiN(111) is much weaker, with preferred adsorption in the top site. Calculated elastic-energy contributions yield a higher stability for κ–Al2O3 on TiN(111) than on TiC(111) and a higher stability for κ–Al2O3 than for α–Al2O3 on both TiC and TiN. This indicates that the observed higher stability of κ–Al2O3 on TiC(111) than on TiN(111) is not due to the lattice mismatch, while the preferred epitaxial growth of κ–Al2O3 over α–Al2O3 can be partly attributed to the mismatch. [Copyright &y& Elsevier]

Crystallization from a cobalt base Co65Si15B 14Fe4Ni2 amorphous magnetic alloy yielded an interesting highly modulated nanolamellar structure with lamellar spacing of about 5 nm. Coarsening of this structure was investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), convergent beam electron diffraction (CBED), and X-ray electron dispersive spectrum (XEDS) techniques and was found to initiate at grain boundaries, which provided nucleation sites for equilibrium phases. Rod-shaped Co2B precipitates were observed along the nanolamellae; such precipitates also played a role in coarsening. A coarse lamellar structure subsequently developed which eventually broke up into equiaxed grains. A metastable Co3Si phase was also observed to form by an allotropic transformation. The coarsening of the nanolamellar structure was found to occur largely by discontinuous coarsening processes. The crystallographic relationship between the equilibrium and metastable phases was determined [ABSTRACT FROM PUBLISHER]

Determining transmission electron microscope specimen thickness is an essential prerequisite for carrying out quantitative microscopy. The convergent beam electron diffraction method is highly accurate but provides information only on the small region being probed and is only applicable to crystalline phases. Thickness mapping with an energy filter is rapid, maps an entire field of view and can be applied to both crystalline and amorphous phases. However, the thickness map is defined in terms of the mean free path for energy loss (λ), which must be known in order to determine the thickness. Convergent beam electron diffraction and thickness mapping methods were used to determine λ for two materials, Si and P91 steel. These represent best- and worst-case scenario materials, respectively, for this type of investigation, owing to their radically different microstructures. The effects of collection angle and the importance of dynamical diffraction contrast are also examined. By minimizing diffraction contrast effects in thickness maps, reasonably accurate (±15%) values of λ were obtained for P91 and accuracies of ±5% were obtained for Si. The correlation between the convergent beam electron diffraction-derived thickness and the log intensity ratios from thickness maps also permits estimation of the thickness of amorphous layers on the upper and lower surfaces of transmission electron microscope specimens. These estimates were evaluated for both Si and P91 using cross-sectional transmission electron microscopy and were found to be quite accurate. [ABSTRACT FROM AUTHOR]

A simple and robust method to precisely determine local strain fields using energy-unfiltered convergent-beam electron diffraction is presented. This method involves the subtraction of background intensity, the extraction of higher-order Laue-zone lines by tracing using a Radon transformation and a system of analytical strain determination without the need for an optimization routine such as χ2-based minimization. As an example, the measurement of residual strain in a silicon-on-insulator wafer is demonstrated. It is found from micro-Raman spectroscopy analysis that, at the nanometre scale, this measurement succeeds with an accuracy of 0.06%. [ABSTRACT FROM AUTHOR]