bluuebunny/crossref_metadata_2025_split huggingface dataset:
Possible applications of fraunhofer holography in high resolution electron microscopy
Authors: Bonnet N. , Troyon M. , Gallion P. 
Published: June 2020

Two main problems in high resolution electron microscopy are first, the existence of gaps in the transfer function, and then the difficulty to find complex amplitude of the diffracted wawe from registered intensity. The solution of this second problem is in most cases only intended by the realization of several micrographs in different conditions (defocusing distance, illuminating angle, complementary objective apertures…) which can lead to severe problems of contamination or radiation damage for certain specimens.Fraunhofer holography can in principle solve both problems stated above (1,2). The microscope objective is strongly defocused (far-field region) so that the two diffracted beams do not interfere. The ideal transfer function after reconstruction is then unity and the twin image do not overlap on the reconstructed one.We show some applications of the method and results of preliminary tests.Possible application to the study of cavitiesSmall voids (or gas-filled bubbles) created by irradiation in crystalline materials can be observed near the Scherzer focus, but it is then difficult to extract other informations than the approximated size.
A simple way for producing holographic filters suitable for image improvement
Authors: Herrmann K.-H. , Reuber E. , Schiske P. 
Published: June 2020

Aposteriori deblurring of high resolution electron micrographs of weak phase objects can be performed by holographic filters [1,2] which are arranged in the Fourier domain of a light-optical reconstruction set-up. According to the diffraction efficiency and the lateral position of the grating structure, the filters permit adjustment of the amplitudes and phases of the spatial frequencies in the image which is obtained in the first diffraction order.In the case of bright field imaging with axial illumination, the Contrast Transfer Functions (CTF) are oscillating, but real. For different imageforming conditions and several signal-to-noise ratios an extensive set of Wiener-filters should be available. A simple method of producing such filters by only photographic and mechanical means will be described here.A transparent master grating with 6.25 lines/mm and 160 mm diameter was produced by a high precision computer plotter. It is photographed through a rotating mask, plotted by a standard plotter.
On a generalized view of holography in relation to the phase problem in electron microscopy
Authors: Lannes A. 
Published: June 2020

Let xO = ϕ (ζ1, ζ2) the object wave function describing a given wave function in a given plane, and let x be its "projection" in the complex Hilbert space E corresponding to the (sampled) domain under consideration. Let U1,…, Uj, …, Up be unitary operators in E, and let J be the "intensity mapping" :xk denotes the kth component of x (for simplicity, we assume that E is finite dimensional). The wave-retrieval (or wave-reconstruction) problem in holography is to solve simultaneous equations of the form :where some components xk are known a priori. JoUj denotes the mapping involved in the formation of the hologram yj. for example, when Uj the is the operator involved in Fresnel's diffraction, yj. is said to be a Fresnel hologram. Likewise, when Uj corresponds to the Fourier transform, yj is said to be a Fourier-transform hologram.
Imaging and diffraction from localized defects and disorder in crystals
Authors: Cowley J.M. , Fields P M. 
Published: June 2020

The atomic arrangements in local perturbations of a crystal structure may be investigated by studying the diffuse scattering in diffraction patterns. Alternatively, for isolated perturbations the atom arrangements may well be imaged directly by high resolution electron microscopy in the near future. For either approach, realistic estimates are necessary of the nature and magnitude of dynamical effects in diffuse scattering. For neither case can the commonly used assumption of the column approximation suffice and the kinematical approximation is rarely relevant.Calculations of dynamical scattering amplitudes, for isolated defects can be made by use of an artificial super-lattice with one defect per superlattice unit cell and a multislice calculation with slice content varying in the propagation direction. Calculations of images and diffraction patterns for split interstitials in Au and A1, with and without lattice relaxation have been reported by Fields and Cowley. Figure 1 shows images and diffraction patterns calculated for a single [100] split interstitial in Au with no relaxation followed by various thicknesses of perfect crystals, with 1MeV electrons, Cs = 1.8mm and objective aperture radius uo = 0.45Å-1.
Lattice imaging and pore structure of β ferric oxyhydroxide
Authors: Baird T. , Fryer J.R. , Galbraith S.T. 
Published: June 2020

Introduction Previously we had suggested (l) that the striations observed in the pod shaped crystals of β FeOOH were an artefact of imaging in the electron microscope. Contrary to this adsorption measurements on bulk material had indicated the presence of some porosity and Gallagher (2) had proposed a model structure - based on the hollandite structure - showing the hollandite rods forming the sides of 30Å pores running the length of the crystal. Low resolution electron microscopy by Watson (3) on sectioned crystals embedded in methylmethacrylate had tended to support the existence of such pores.We have applied modern high resolution techniques to the bulk crystals and thin sections of them without confirming these earlier postulatesExperimental β FeOOH was prepared by room temperature hydrolysis of 0.01M solutions of FeCl3.6H2O, The precipitate was washed, dried in air, and embedded in Scandiplast resin. The sections were out on an LKB III Ultramicrotome to a thickness of about 500Å.
Analysis and lattice imaging of a transitional event on garnets
Authors: Laval J.Y. 
Published: June 2020

The exsolution of magnetite from a substituted Yttrium Iron Garnet, containing an iron excess may lead to a transitional event. This event is characterized hy the formation of a transitional zone at the center of which the magnetite nucleates (Fig.1). Since there is a contrast between the matrix and these zones and since selected area diffraction does not show any difference between those zones and the matrix in the reciprocal lattice, it is of interest to analyze the structure of the transitional zones.By using simultaneously different techniques in electron microscopy, (oscillating crystal method microdiffraction and X-ray microanalysis)one may resolve the ionic process corresponding to the transitional event and image this event subsequently by high resolution technique.
Lattice imaging of Pd2Si thin films
Authors: Kuan T.S. , Tu K.N. 
Published: June 2020

Thin films of near-noble metal silicide such as Pd2Si and PtSi are now being used as rectifying and ohmic contacts in high performance Si devices. These silicides are made by depositing and annealing the metals on Si. The substrate temperature and orientation and the annealing condition can affect the microstructure of the silicide (1) and in turn change the electrical characteristics of the contact.This study attempts to show that detailed structural information about thin Pd2Si films can be obtained from lattice imaging technique. We chose the Pd2Si because it has a hexogonal structure (2) and grows epitaxially on (111) Si with the orientation relationships:(001)Pd2Si // (111)Si and [100]Pd2Si // [110]Si. The epitaxially-grown film will provide a large area or the single crystal Pd2Si for lattice imaging.The Si wafers used were n-type, 10 to 20 Ω-cm, (111) oriented, and HF etched before deposition. The deposition of Pd film of 100Å was carried out by e-beam evaporation at a rate of ∼5Å/sec. in a vacuum of 2x10-7 torr onto room temperature substrates.
Low resolution STEM imaging
Authors: Hutchings R. , Jones I.P. , Loretto M.H. 
Published: June 2020

IntroductionIn recent papers (Fraser and Jones 1975, Fraser, Jones and Loretto 1977) it has been shown that STEM does not offer an increase in penetration of metallurgical specimens over that available in CTEM. It was argued that two factors, lack of intensity and a top/bottom effect, limit penetration in both CTEM and STEM and the relative importance of these factors is expected to differ for different experimental requirements. The present paper examines an experiment with requirements such that the intensity limit in STEM may be overcome by using a large probe of about 40nm diameter.ExperimentalSpecimens of a complex copper alloy (Long 1977) containing particles of Cr (∼10nm in diameter) and particles of SiO2 (∼0.5 μm in diameter) have been examined at 100kV in STEM and CTEM using a Philips EM40O fitted with a conventional tungsten hairpin filament. In addition micrographs have also been obtained at 1MV in an AEI EM7. The contrast mechanism was of structure factor type.
Bright field and weak-beam images of dislocations gliding on (001) planes in F.C.C. metals
Authors: Karnthaler H. P. , Korner A. 
Published: June 2020

In f.c.c. metals slip is observed to occur generally on {111} planes. Glide dislocations on intersecting {111} planes can react with each other and form Lomer-Cottrell locks which lie along a <110> direction and are sessile since they are split on two {111} planes. Cottrell already pointed out that these dislocations could glide on {001} planes if they were not split. The first study of this phenomenon has been published recently. It is the purpose of this paper to report some interesting new details of the dislocations gliding on {001} planes in pure Ni, Cu, and Ag deformed at room temperature.Single crystals are grown with standard orientation and strained into stage II. The crystals are sliced parallel to the (001) planes. The dislocation structure is studied by TEM and the Burgers vectors ḇ and glide planes of the dislocations are determined unambiguously.In Fig.l primary P and secondary S dislocations react and form composite dislocations K.
A transmission electron microscope study of the complex annealing behaviour of amorphous layers due to ion implantation in silicon
Authors: Drosd R. 
Published: June 2020

It is well known that very high dose ion implantation of Si results in an amorphous (α) layer. However, the annealing of this α layer with its complicated dependence on such variables as implant species, implantation dose and temperature, crystal orientation, and thermal history is not well understood. Many of the past studies have employed the ion chanelling technique to study the crystallization of the α layer. Although this technique gives useful information concerning the α layer thickness, it tells little about the type and density of defects present. Hence the electron microscope gives unique information of the detailed mechanism of crystallization of α Si layers.One of the most striking features of the annealing behaviour is its dependence on the crystal orientation. Previous studies indicate the (111) orientation crystallizes much more slowly than the (100), leaving behind a high density of stacking faults and twins.
Radiation enhanced precipitation and dissolution of precipitates investigated by transmission electron microscopy
Authors: Kesternich W. 
Published: June 2020

Ni-Cr-Fe alloys are the basis for a large family of super alloys and structural steels to be applied in fast breeder and fusion reactor components. A program has been started in Jülich to investigate the point defect kinetics and irradiation induced phase instabilities in pure Ni-Cr-Fe alloys. Fig. 1 shows the change of electrical resistivity as a function of annealing temperature of a homogenized unirradiated Ni75-Cr13-Fe alloy and of the same alloy after electron irradiation and after α-irradiation. The increase of the resistivity and its subsquent decrease is explained by clustering of atoms and subsequent precipitation.Effects of clustering in the unirradiated and electron irradiated specimens cannot be detected by transmission electron microscopy. Aging at 500 and 600°C for 250 hours also does not reveal any microstructural changes by TEM. After °-irradiation, however, precipitates as well as dislocation loops show up as black spot or black-white contrast depending on the imaging conditions Fig. 2
Determination of the structural aspects of favored grain boundary reaction sites
Authors: Gronsky Ronald , Thomas Gareth 
Published: June 2020

Of the techniques which have been employed in the study of grain boundary precipitation reactions, none have demonstrated sufficient resolution to directly reveal the structural characteristics of active nucleation sites. This information is vital since many existing interpretations of conventional TEM data are in conflict.The present paper describes an application of high resolution electron microscopy which distinguishes atomic level details in both the boundary and growth front regions of grain boundary precipitates, and indicates the structure and mechanisms responsible for enhanced reaction kinetics.Experiments were performed on an Al-9.5 at.% Zn alloy aged for 30 mins, at 180°C to encourage heterogeneous nucleation at grain boundaries. Two examples of early stage grain boundary precipitates are shown in Fig. 1, both of which have been nucleated in the lower grain. It is seen that in (b) the precipitate is much more sharply faceted than in (a). Notably the orientation of the grain boundary plane is very near to that of the close-packed {111} matrix planes of the lower grain for precipitate (b), whereas the boundary is sharply inclined to {111} for precipitate (a).
Electron microscopy studies of grain boundary segregation in α Al2O3
Authors: Krivanek Ondrej L. , Harmer Martin , Geiss Roy 
Published: June 2020

Solute segregation at grain boundaries is a common phenomenon in ceramic systems. Under certain circumstances it can lead to a reduction in the boundary migration rate by an impurity drag mechanism. This favours pore attachment to grain boundaries during the later stages of sintering and allows high densities to be achieved. To interpret the sintering data one needs to know the spatial distribution of the additives, and how the additives affect the defect structure of the material. Spatial distributions can be measured by Auger electron spectroscopy, but this technique cannot distinguish additives present as separate second phase from those in solid solution, and is restricted to materials that fracture intergranularly.In alumina, the standard sintering additive is MgO, but TiO2 can be used where hardness of the sintered material is important. We have studied Al2O3 doped with 0.1 w/o TiO2. Thin foils were prepared by ion beam milling, and examined by 1) conventional electron microscopy to investigate the grain and pore structure of the material, 2) high resolution lattice imaging to test for the presence of intergranular phases at grain boundaries, and 3) X-ray microanalysis to probe the Ti concentration profile across grain boundaries and near pore surfaces.
Hardening effects of grain boundary defect structure
Authors: Venkatesh Eswarahalli S. , Murr L.E. 
Published: June 2020

The grain boundary defect structure can be changed to advantage by appropriate mechanical and thermal treatments. Researchers continue to show interest in understanding the effects of boundary defect structure on the mechanical properties of polycrystalline metals and alloys. Grain boundary structural features such as boundary ledges have been considered as a means of strengthening in metals and alloys. Considering the various models of Hall-Petch analyses, the grain boundary strength, σg can be expressed as σg = 8αGb(l-υ)m(L/ℓ); where m is the grain boundary ledge density, L is the grain size, ℓ is the distance of dislocation source in the adjacent grain matrix from the boundary, and G, b, and υ have the usual meaning. In particular, the influence of grain boundary ledge density on the strength (hardness) of grain boundaries is considered in the present paper.In the present investigation, pure (99.98%) nickel sheet mill (hot) rolled to 0.022 in. thick was used.
Investigation of boundary structure of copper phthalocyanine crystal grains in resolving crystallographic planes
Authors: Natsvlishvili G.I. 
Published: June 2020

Deformed crystals of copper phtalocyanine have been investigated. The crystals were deformed in the process of grinding. Large angle grain boundaries with good resolution of dislocations and crystallographic planes (001) have been detected in the electron microscope JEM-100 C.Fig1 shows the grain dislocation boundary with disorientation angles ≈ll.5°.Attention should be paid to the asymmetry of the boundary. The boundary for the left side grain is almost parallel to the plane (100), while the atomic planes of the right side grain break off at the boundary at a distance of ≈65 Å from each other. The measured Burgers vector (b=12.6 Å) and the distance between the dislocations in the wall correspond to the measured disorientation angle.If the image of the region of ‘perfect’ lattice is projected from the same negative under the photographic enlarger on the printed photograph, it will be easy to see that the elastic fields of dislocation forming the boundary given in fig. 1 are also asymmetric.
A RMEED and SEM investigation of metal oxidation phenomena
Authors: Hembree G.G. , Cowley J.M. , Otooni M.A. 
Published: June 2020

We have recently completed an in-situ study of the reaction of copper thin films at low oxygen pressures (10-5 torr) and relatively high temperatures (500-700°C).These conditions allow convenient observation over reasonably short reaction times in our UHV RMEED/SEM instrument(1).Epitaxially grown (111) copper films of approximately 100nm thickness were prepared in a conventional HV system and placed in the UHV system as produced on their mica substrates. Epitaxy was confirmed by TED/TEM on pieces of the film which were stripped off the substrate and by the electron channeling patterns observed in the SEM. Initial treatment in the UHV system included annealing at 300°C for several hours and a final anneal at 500°C for one hour. In one case the film was sputter cleaned with a 700eV argon ion beam between the two annealing processes. Some oxide nuclei of various sizes were observed after this treatment.After the initial cleaning pure copper reflection diffraction patterns as in Fig.1 were recorded up to the sixth order.
Strip domains in Nife single and multilayer thin films with inplane magnetization
Authors: Herd S.R. , Ahn K.Y. 
Published: June 2020

In this paper we attempted to correlate the microstructure of single and multilayered NiFe (80/20) films with the magnetic domain structure as a function of coercivity Hc and film thickness below 700Å. The films were prepared by either E-beam evaporation or rf-sputtering onto carbon covered mica at RT. All films were coated with a protective layer on both top and bottom surfaces, as well as a spacer layer in the case of the multilayered films, of either SiO or SiO2.The Hc was found to drop sharply with increasing thickness from >10 oe to 6 oe between 10Å and 30Å which could be attributed to the diminishing island structure. At 30Å well separated, 200-300Å sized islands contain many small grains of up to 30Å size. Island size then decreases while the grainsize increases with thickness until a residual void network is formed around indivudial grains of size comparable to the thickness.
Orthopyroxene to talc transformation
Authors: Boland J.N. , Eggleton R.A. 
Published: June 2020

Mineralogical transformations that occur during the weathering of rocks are complex processes involving both physical and chemical changes. Although it may be difficult to relate the primary minerals to the secondary phases of the weathering process, there is evidence that certain transformations occur topotaxially. The clinopyroxene, hedenbergite, alters to montronite, an iron-rich montmorillonite mineral, topotaxially; the transformation has been modelled by a crystallographic shear of 1/2[101] on (100) of the pyroxene. This shear mechanism converts the chain silicate into a sheet structure. A similar process may be postulated for several other pyroxene alterations. The commonly observed orthopyroxene to talc transformation has been studied in detail using electron microscopy, electron microprobe, optical microscopy and x-ray diffraction.The process has been studied in an interaction zone that develops between unaltered orthopyroxene and talc layers formed along grain boundaries and within cracks. The growth of the interaction zone occurs by the migration of the interface into the unaltered orthopyroxene-Fig. 1.
Characterization of polymeric materials by TEM
Authors: Russell R.R. 
Published: June 2020

Structural characterization of the expanding cavalcade of engineering polymers is now as important to the materials application engineer as to the basic researcher. Direct transmission electron microscopy (TEM) is the primary method for delineation and evaluation of microstructures in many polymer blends and composites and thus plays a major role in characterization studies.Only TEM clearly resolves structural components, such as phases and fillers in many polymeric materials. This technique can also reveal the effects of strain (crazing, shearing or phase deformation) in polymer microstructures. Thus, by utilizing TEM, bulk structural documentation (Figure 1) as well as the results of laboratory testing (Figure 2) or manufacturing processes can be studied.Basic to successful direct TEM structural characterization of any material are reliable sample preparation techniques capable of producing thin samples which retain the true features of the bulk material.Ultramicrotomy is used extensively for producing such thin samples from polymers.
Determination of the phase structure of polymerblends by electron microscopy
Authors: Kaemof Dr. G. 
Published: June 2020

A mixture of polycarbonate (PC) and styrene-acrylonitrile-copolymer (SAN) represents a very good example for the efficiency of electron microscopic investigations concerning the determination of optimum production procedures for high grade product properties.The following parameters have been varied:components of charge (PC : SAN 50 : 50, 60 : 40, 70 : 30), kind of compounding machine (single screw extruder, twin screw extruder, discontinuous kneader), mass-temperature (lowest and highest possible temperature).The transmission electron microscopic investigations (TEM) were carried out on ultra thin sections, the PC-phase of which was selectively etched by triethylamine.The phase transition (matrix to disperse phase) does not occur - as might be expected - at a PC to SAN ratio of 50 : 50, but at a ratio of 65 : 35. Our results show that the matrix is preferably formed by the components with the lower melting viscosity (in this special case SAN), even at concentrations of less than 50 %.
Analytical TEM of the discontinuous reaction in Cu-Be-Co alloys
Authors: Williams D.B. 
Published: June 2020

The discontinuous reaction in commercial Cu-1.87%Be,-0.257%Co alloys has been observed in a TEM/STEM. Microdiffraction has been used to determine precipitate/ matrix orientation relationships and high resolution X-ray microanalysis has enabled the effect of the Co on the discontinuous and continuous precipitation reactions to be studied.Discs of Cu-Be, solution treated at 800°C for 1 hour were water quenched and aged for varying times between 175°C and 340°C. Thin foils were prepared by jetelectropolishing with a solution of 30% HNO3 in methanol at -50°C and 25 volts. All foils exhibited the discontinuous reaction which occurs at grain boundaries only and consists of alternate lamellae of the α Cu-Be solid solution and the metastable intermediate γ' (CuBe) phase which grow at the expense of homogeneous matrix γ'. A typical STEM micrograph of the reaction is shown in fig. 1. The γ' precipitates, initially ascribed erroneously to the presence of a G.P. zone solves, were later identified as a B2 superlattice structure with a=0.27nm, although evidence for superlattice spots has been disputed.