bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of ferroelectrics using conventional and in situ electron microscopy
Authors: Saikumar V. , Chan H. M. , Harmer M. P. 
Published: June 2020

In recent years, there has been a growing interest in the application of ferroelectric thin films for nonvolatile memory applications and as a gate insulator in DRAM structures. In addition, bulk ferroelectric materials are also widely used as components in electronic circuits and find numerous applications in sensors and actuators. To a large extent, the performance of ferroelectric materials are governed by the ferroelectric domains (with dimensions in the micron to sub-micron range) and the switching of domains in the presence of an applied field. Conventional TEM studies of ferroelectric domains structures, in conjunction with in-situ studies of the domain interactions can aid in explaining the behavior of ferroelectric materials, while providing some answers to the mechanisms and processes that influence the performance of ferroelectric materials. A few examples from bulk and thin film ferroelectric materials studied using the TEM are discussed below.Figure 1 shows micrographs of ferroelectric domains obtained from undoped and Fe-doped BaTiO3 single crystals. The domain boundaries have been identified as 90° domains with the boundaries parallel to <011>.
Effect of energy filtering on micro-diffraction in the SEM
Authors: Mancuso James F. , Fama Leo A. , Maxwell William B. , Lehman Jerry L. , Weiland Hasso , Biederman Ronald R. 
Published: June 2020

Micro-diffraction based crystallography is essential to the design and development of many classes of ‘crafted materials’. Although the scanning electron microscope can provide crystallographic information with high spatial resolution, its current utility is severely limited by the low sensitivity of existing diffraction techniques (ref: Dingley). Previously, Joy showed that energy filtering increased contrast and pattern visibility in electron channelling. This present paper discribes the effect of energy filtering on EBSP sensitivity and backscattered SEM imaging.The EBSP detector consisted of an electron energy filter, a microchannel plate detector, a phosphor screen, optical coupler, and a slow scan CCD camera. The electrostatic energy filter used in this experiment was constructed as a cone with 5 coaxial electrodes. The angular field-of-view of the filter was approximately 38°. The microchannel plate, which was the initial sensing component, had high gain and had 50% to 80% detection efficiency for the low energy electrons that passed through the retarding field filter.
EBSP: A powerful tool in studying recrystallization of metals
Authors: Furu T. , Lohne O. , Sødahl Ø. , Nes E. 
Published: June 2020

The Electron Back Scattering Pattern Technique (EBSP), for measurements of crystal orientations is now a well established technique for microtexlure detennination. The application of the technique to material problems has increased quite substantially the last years, both in basic research and in more industry related problems. When studying the recrystallization process in detail a relatively large area of a specimen has to be investigated to obtain good statistical results. With a resolution of the order of 0.5-1 μm and a short processing time the EBSPtechnique has shown to be advantageous compared to TEM on one side and X-ray and neutron diffraction on the other. By the EBSP-technique we are able to follow the local texture evolution during transformation and are at the same time able to analyse changes in the untransfonncd matrix (i.e. subgrain growth etc.).It is well accepted that the formation of recrystallization nuclei is a highly heterogeneous process.
The texture between grains
Authors: Randle V. 
Published: June 2020

The ‘texture between grains’, sometimes called mesotexture, refers to the distribution of geometry/crystallography at grain boundaries and grain junctions (edges). These parameters can be accessed from measurements of individual grain orientations, and the most efficient means of collecting such data is by electron back-scatter diffraction (EBSD) in a scanning electron microscope. The reason for studying the texture at grain boundaries and junctions, on an individual basis, is that the properties of these defects (e.g. energy, mobility, diffusivity, resistivity etc) is geometry-dependent. It is desirable to investigate the nature of this relationship and how improved grain boundary properties might be achieved.The following information can be obtained:1.Misorientation across grain boundaries, allowing them to be classified as low/high angle, and according to the coincident site lattice model.2.The orientation of the grain boundary surface (plane) itself with respect to the lattice of each neighbouring grain.3.Classification of grain junctions as I-lines (dislocation balance) or U-lines (dislocation imbalance).4.The connectivity between grain boundaries, or between the grain boundary/junction networks.
Identifying fracture mechanisms with the EBSP technique
Authors: Slavik D. C. 
Published: June 2020

Stress corrosion cracking (SCC), liquid metal embrittlement, and corrosion fatigue cracking mechanisms can be evaluated by measuring grain boundary misorientations along the crack path or the crystallography of fracture surface facets. The crystallographic orientation of individual grains can be measured with back Laue, Kikuchi, selected area channelling pattern (SACP), or electron back scatter pattern (EBSP) techniques. EBSPs are unique since a large statistical sampling of individual grains or subgrains as small as a micrometer in diameter can be probed on single large samples.For intergranular fracture, low angle and coincident site boundaries (twins as an example) are typically SCC resistant compared to general high angle grain boundaries. This observation, important for modeling fracture or improving microstructural performance, can be identified by sampling boundaries in the matrix and along the fracture path with EBSP or SACP techniques.Transgranular fatigue mechanisms, dramatically influenced by the test environments for Al-Li-Cu alloys as shown in Figures 1a and b, can be identified my measuring fracture facet crystallographic orientations.
Microstructural characterization of interface-engineered Si3N4 for improved fracture toughness and wear resistance
Authors: Ghosh G. , Vaynman S. , Fine M. E. 
Published: June 2020

Due to its low density, high strength and high modulus, Si3N4 is a potential candidate as a wear-resistant material. However, the fracture toughness of Si3N4 is rather poor. It is well known that the fracture toughness of ceramics can be increased by introducing compressive residual stress at the surface. This can be achieved by forming a chemical layer having lower coefficient of expansion at high temperature and then cooling the sample to room temperature. Improvement of wear resistance of Si3N4 by surface modification with Al2O3 has been demonstrated. Here we have studied the strengthening of polycrystalline Si3N4 by producing compressive stresses at all grain boundaries throughout the sample.Polycrystalline Si3N4 (predominantly β-phase) powders were coated with Al2O3, dried, hot pressed and sintered at 1650°C to form Sialon at the grain boundaries. Both conventional TEM and AEM were performed to examine the as-coated powders and the samples after hot-pressing and sintering.
Nanometric plasticity in diamond-turned germanium
Authors: Callahan D. L. , Morris J. C. , Kulik J. , Patten J. A. , Scattergood R. O. 
Published: June 2020

This study applies transmission electron microscopy to the analysis of anomalous ductility encountered in the diamond-point turning of semiconducting Ge. Both finished surfaces and turnings are examined. The machined surface exhibits fine parallel tool marks decorated with randomly oriented nanocrystalline Ge fragments as shown in FIG 1. The tool marks are periodic with a period corresponding to a feed pass. The fragments are the displaced debris which remain between each pass of the diamond tool. There are no indications of substantial dislocation activity or microcracks extending below this surface.A fine Ge chip exhibiting a ductile removal morphology is shown in FIG. 2. This type of turning shows fine periodic tool marks as seen on the finished surfaces (FIG. 1) and thickness modulations perpendicular to the tool marks. These thickness modulations are identical to discontinuous shear patterns reported in soft metals turning and point to a shear slip-dominated deformation process; in fact, the general morphology of these chips is virtually indistinguishable from that observed in fine aluminum turnings.
Phase separation in sol gel-derived ceramic films of silica-zirconia, alumina-zirconia, and titania-zirconia system
Authors: Tong J. , Eyring L. 
Published: June 2020

There is increasing interest in composites containing zirconia because of their high strength, fracture toughness, and its great influence on the chemical durability in glass. For the zirconia-silica system, monolithic glasses, fibers and coatings have been obtained. There is currently a great interest in designing zirconia-toughened alumina including exploration of the processing methods and the toughening mechanism.The possibility of forming nanocrystal composites by a phase separation method has been investigated in three systems: zirconia-alumina, zirconia-silica and zirconia-titania using HREM. The morphological observations initially suggest that the formation of nanocrystal composites by a phase separation method is possible in the zirconia-alumina and zirconia-silica systems, but impossible in the zirconia-titania system. The separation-produced grain size in silica-zirconia system is around 5 nm and is more uniform than that in the alumina-zirconia system in which the sizes of the small polyhedron grains are around 10 nm. In the titania-zirconia system, there is no obvious separation as was observed in die alumina-zirconia and silica-zirconia system.
Amorphization of Al10(Vx,Cr1-x) intermetallic phase
Authors: Radmilovic V. , Kilaas R. , Thomas G. 
Published: June 2020

The stability of phases in alloy systems, including stability in irradiation environments, is conditio sine qua non of their engineering applications. Thus, investigations of different phenomena, such as compositional variation, segregation, order/disorder transitions and amorphization in different phases under irradiation, is of great importance.In the present paper experiments are reported on using high resolution electron microscopy and electron diffraction to observe the stability of Al-V-Cr based intermetallic phase in Al based alloys which are considered potential material for aerospace applications. In addition, it is an attempt to establish a possible method for investigation of disordering and amorphization in intermetallic phases under the electron beam, as first observed by Thomas et al. in the Ni-Ti system.The Al based alloy with chemical composition (in wt.%) Al - 2.3 Li - 1.0 Cu - 0.8 Mg - 1.0 Cr - 1.0 V - 0.5 Zr was solutionized at 530°C for 4 hours, water quenched, and aged for 48 hours at 148°C.
Transmission Electron Microscopy of Mercury Sulfide Particles From A Mercury-Contaminated Soil
Authors: Stevenson R. , Harris L. , Turner R. , Barnett M. 
Published: June 2020

Presently the East Fork Poplar Creek (EFPC) floodplain located in the city of Oak Ridge, Tennessee and adjacent to the Y-12 nuclear plant is reportedly contaminated with mercury. The metallic mercury which was used from 1955 to 1963 in the production of lithium enriched in the 6Li isotope, is the source of the present contamination.Previous analyses of these soils using electron probe micro-analysis (EPM) and scanning electron microscopy (SEM) revealed mercury to be present principally as discrete micrometer and submicrometer size particles which were observed to coexist with sulfur. These observations suggested that mercury might be present as mercury sulfide (perhaps even in a crystalline form) which could then affect the level of remediation required for this soil since the toxicity and mobility of mercury is dependent upon its speciation.The limited concentration of mercury in the EFPC soils (3000-100 mg/kg) and the relatively small size of these mercury bearing particles makes transmission electron microscopy (TEM) the ideal analytical method for unequivocally identifying these particles with micro-chemistry and select area electron diffraction (SAED).
Recent developments of the tomographic atom probe
Authors: Deconihout B. , Menand A. , Blavette D. 
Published: June 2020

Today material science requires the use of increasingly powerful tools in materials analysis. The last twenty years have witnessed the development of a number of analytical techniques. However, though the arsenal of these techniques is large today, only a few instruments allow both observation and analysis of materials at the nanometer level. One can mention secondary ions mass spectrometry technique (SIMS), scanning transmission electron microscopy coupled with electron energy loss spectrometry (STEM-EELS) and atomprobe techniques. In the SIMS technique, only in-depth spatial resolution can reach one nanometer since lateral spatial resolution is related to the incident ions beam diameter namelya few tenth of micrometers. On the contrary, in the STEM-EELS technique, the lateral spatial resolution can be as good as one nanometer while the in-depth spatial resolution is rather poor ; this last resolution is determined by the specimen thickness and therefore strongly depends on samples preparation.Atom-probe techniques makes it possible to investigate a material with both a high lateral and in-depth spatial resolution. Indeed, the spatial resolution reached with the atom-probe can be lower than one nanometer at the sample surface while being strictly equal to an atomic layer in-depth.
Faster turnaround time for TEM by using a multiple-sample approach
Authors: Alvis Roger , Tracy Bryan 
Published: June 2020

The many advantages of transmission electron microscopy (TEM) over other microscopy techniques areoften offset only by one drawback: slow turnaround time. Because of the fact that the time required to complete a multi-sample analysis is directly proportional to the number of samples submitted, TEM is often not a viable tool to analyze an entire fabrication process run or a multi wafer process development experiment. However, we have developed a technique that has allowed a single person to prepareas many as six cross-sectional TEM samples in one day thereby affording the opportunity for the investigation of an entire experimental matrix in a relatively short time.This improvement in throughput is achieved by our approach to sample preparation which combines features of the Bravman-Sinclair method with the Tripod polishing technique developed by Benedict and wide tool dimpling described by Humiston. In essence, the standard dummy dice of the Bravman techniqueare replaced by "real" device dice which have been thinned to less than 50°m using the Tripod polisher. This type of mechanical back lapping was first suggested by Marcus and Sheng. Our experiments with this type of sample preparation have been applied to both failure analysis and process development applications.
TEM characterization of SiGeC material system
Authors: Chandrasekhar D. , Smith David J. , Kouvetakis J. , Robinson McD. 
Published: June 2020

The IV-IV material system, specifically Si1-xGex/Si, has generated considerable interest in the scientific community in recent years. The built-in compressive strain and composition of pseudomorphic Si1-xGex epilayers on Si substrates affect the band structure and energy gap, which are fundamental to bandgap engineering. This property has been used in demonstrating a heterojunction bipolar transistor with SiGe base, resulting in improved high-frequency performance over conventional transistors with Si bases. However, the thermal instability and lower critical thickness of Si1-xGex layers limits applications, in turn prompting investigation of the Si1-x-yGexCy system. Substitutional carbon incorporation in Si1-xGex is expected to relieve the strain in the epilayer and increase the energy gap, the latter being an important consideration in revolutionizing transistor technology. Recently, growth and characterization of pseudomorphic Si1-x-yGexCy and its photoluminescence properties have been reported.In our present study, we have characterized Si1-x-yGexCy samples grown on Si substrates by chemical vapor deposition. Different precursors and flow rates were used tovary the relative elemental compositions. Rutherford backscattering and secondary ion mass spectroscopy techniques were employed for compositional analysis and transmission electron microscopy was used to determine microstructure. Electron transparent specimens were prepared in cross-section by a standard technique, involving mechanical grinding, dimpling and argon ion-milling. TEM observations were made with JEOL 2000FX and JEOL 4000EX microscopes. Selected area diffraction patterns and optical diffractograms were used in determining the structure and lattice constants.
Transmission Electron Microscopy of polysilicon microresistor
Authors: Duan J. Z. , Thomas B. , Sidhwa A. , Chopra S. 
Published: June 2020

The electrical properties of electronic materials are greatly affected by their microstructure, which in turn is determined by the processes used for fabrication. Transmission Electron Microscopy (TEM) is one of the most powerful analytical techniques to provide localized information about microstructure as it relates to process control parameters. This information is used for process development and failure diagnoses as well as QA/QC control. In this study, the microstructures within the devicesof polysilicon microresistors were analyzed using TEM to understand different resistances.The TEM samples were prepared from the devices to be analyzed by the mechanical polishing method using the tripod polisherTM. The selected area polishing technique was used to find the area of interest within one micron range. Figure 1 shows the specimen preparation process. The low and high magnification optical micrographs in Figures 1a and 1b indicate the region of interest within the die. Figure 1c is the optical image of the cross section along the line A-A in Figure lb.
Columnar microstructures of preferred oriented Aluminum Nitride films prepared by reactive sputtering
Authors: Kim Geun-Hong , Lee Hwan-Chul , Chun Chang-Hwan , Lee Jai-Young 
Published: June 2020

Aluminum nitride (AIN) thin films have drawn much attention as piezoelectric materials for generation and detection of surface acoustic wave (SAW) owing to high ultrasonic velocity and fairly large piezoelectric coupling factors. Since the piezoelectric properties are strongly dependent upon the c-axis orientation of AIN films, it is important to control the crystallographic orientation with deposition parameters. Though many reports have been presented, the mechanism of crystallographic orientation change with deposition parameters still remains unknown and the microstructure analysis of AIN films have been scarcely carried out. In this paper, we present the effect of sputtering pressure on thecrystallographic orientation and the microstruclure of the deposited AIN films, using X-ray diffraction (XRD) and transmission electron microscopy (TEM) study.AIN films have been deposited on Si (100) wafers by reactive RF magnetron sputtering in Ar-N2 gas mixture without substrate heating. The base pressure of vacuum chamber was below 1.5X10-6 Torr, RF power was 200 W and the ratio of gas flow rate (Ar:N2) was 3:1. Processing pressures ranged from 5 to 12 mTorr. Crystal structure of as-deposited films examined with XRD (Rigaku, D/MAX-RC, 12 kW) and microstructure analyses were carried out using crosssectional and plan-view TEM (JEOL 4000FX, 400 kV).
Characterization of constitutional liquid-film migration in Alloy 718
Authors: Acoff V. L. , Griffin R. D. , Thompson R. G. 
Published: June 2020

Alloy 718 is a nickel-based superalloy which consists of an FCC solid solution of Ni, Fe, and Cr strengthened with γ″ precipitates. The composition of the alloy is shown in Table 1. It has excellent high temperature mechanical properties and oxidation resistance. However, Alloy 718 is susceptible to hot cracking in weld heat affected zones (HAZ) as a result of the formation of intergranular liquid. This metastable grain boundary liquid may be due to “constitutional liquation” of second phase particles, known as constitutional liquid film migration (CLFM). Radhakrishnan and Thompson report that CLFM can occur in situ in the weld HAZ of alloy 718 as a result of constitutional liquation.Constitutional liquation can be described in terms of a binary alloy with a phase diagram such as theone shown in Figure 1. If an alloy of composition C° is rapidly heated above theeutectic temperature, TE, to temperature T, the AB particles will not have sufficient time to dissolve, as dictated by equilibrium.
Four-fold aperture synthesis, three-fold astigmatism, and two-fold resolution improvement: Computer-aided microscopy comes of age
Authors: Saxton W. O. 
Published: June 2020

Virtually no electron microscopes are now without internal computer control at least, and externalcomputer support continues to play a more important part every year, fuelled by the hundred-fold increase in computing power over the past five years and the continuing if slow advance in the availability of CCD camera systems for TEM. High resolution electron microscopy is within sight of becoming a well-defined, reproducible, technique in which the variability will be restricted at last to the specimen under investigation. The choice of computer systems has narrowed to Macs, Windows on PCs, or Unixworkstations; the future may be with Windows NT.Image restoration (recovering the specimen exit plane wavefunction) is again the subject of considerable interest as a route to higher resolution, in parallel with biprism holography, and incoherent imaging and ptychography in STEM; and the inverse scattering problem (deducing atomic positions from the scattered wave leaving the specimen) is under active investigation.
Direct retrieval of crystal structures by maximum-entropy analysis of incoherent Z-contrast images
Authors: McGibbon A. J. , Pennycook S. J. 
Published: June 2020

Z-contrast imaging of crystalline specimens in a scanning transmission electron microscope (STEM) can provide directly interpretable images of crystal structures at atomic resolution with strong compositional sensitivity. The key feature of the technique is that, by recording images using high-anglethermally diffuse scattered electrons, the resultant image is incoherent, and can be interpreted as aconvolution between the incident electron probe and the projected crystal structure of the specimen. Consequently, the technique is ideally suited to the application of deconvolution routines which enable the retrieval of the original crystal lattice by means of an incident electron probe approximation, and with no prior assumption of the nature of the crystal itself. Here, we show that by applying the image processing technique of maximum entropy, such a retrieval can be achieved with high accuracy,enhancing spatial resolution whilst preserving Z-sensitivity.Maximum entropy is an image processing routine based on Bayesian probability which produces a ‘most likely’ reconstruction of the original image given a particular point spread function, or in this case, electron probe current density distribution.