Showing papers on "Transmission electron microscopy published in 1982"

The Oxidation of Shaped Silicon Surfaces

Abstract: Nonplanar silicon surfaces were prepared and oxidized at 900°–1100°C and the oxide morphology was studied by transmission electron microscopy of thin sections. A 30% decrease in oxide thickness at silicon step edges following 900° and 950°C wet oxidation is attributed to the effect of locally compressive intrinsic stress within the oxide on the solubility of oxygen. Oxidation inhibition becomes less at higher temperatures due to the relief of stress (during growth) by viscous flow of the oxide.

Composition modulation in liquid phase epitaxial InxGa1−xAsyP1−y layers lattice matched to InP substrates

Abstract: Liquid phase epitaxial layers of InxGa1−xAsyP1−y grown lattice matched to InP〈001〉 substrates, in the concentration range 0.53⩽x⩽0.88, have been studied by transmission electron microscopy. For the usual growth temperatures, solid instability was predicted for compositions in the range 0.55≲x≲0.75. Indeed a quasiperiodic variation of a strain contrast, though very light in some cases, is always observed in the 〈100〉 and 〈010〉 directions in that composition range, and never outside. The pseudoperiodicity is of the order of 1000 A. Local concentration measurements have been performed on one sample using a scanning transmission electron microscope. They show that the strain contrast, quite strong in that sample, is related to a concentration modulation. The measured variations on x and y are as high as 0.1, and they keep the ratio x/y constant, which is consistent with phase separation observed on nucleated InxGa1−xAsyP1−y.

Microstructural Analysis of Sintered High-Conductivity Zirconia with Al203 Additions

Abstract: Transmission electron microscopy (at 100 and 1000 kV potential) and analytical scanning transmission electron microscopy were used to study α-Al203 second-phase particles and their interactions with grain boundaries in two high-conductivity Y203/Yb203 stabilized zirconia ceramics containing deliberate additions of the alumina as a sintering aid. Most of the Al203 particles were intragranular and microanalysis showed that they contained inclusions rich in Zr or Si plus Zr. Al2O3 particles at grain boundaries were frequently associated with amorphous cusp areas rich in Si and Al. The results suggest that the Al203 acts as a scavenger for SiO2, removing it from grain-boundary localities. A model is proposed whereby this process occurs as the boundaries meet the second-phase particles, assisted by rapid grain-boundary diffusion. Such an ZrO2-Al2O3-SiO2 interaction and partitioning is predicted thermodynamically and offers a possible explanation for the improvements in ionic conductivity brought about by Al2O3 additions, as reported in the literature.

Large strain multidirectional deformation of 1100 aluminum at 300 K

Abstract: Multidirectional compression testing of 1100 aluminum cubes at room temperature in three orthogonal directions developed saturation flow stresses at very large accumulated strains. The saturation stress was found to be a function of the strain increment used, and followed a power-law relationship. The results correlated well with fatigue tests of aluminum and alpha iron. Copper data showed a similar but more pronounced behavior. The presence of dislocation cells, subgrains and dislocation tangles dominated the microstructure as observed by transmission electron microscopy. The microstructure changed in a systematic manner with accumulated straining. Significant differences in sizes and concentrations of cells and subgrains were found for unidirectional compared with multidirectional straining. These features were correlated using generally accepted relationships between individual substructural configurations and flow stress.

Transmission Electron Microscopy of Extracted Fulvic and Humic ACIDS1

Abstract: We used a replica technique, in conjunction with transmission electron microscopy, to determine the shape, size, and degree of aggregation of fulvic and humic acid particles deposited on mica by the rapid freezing and drying of dilute aqueous solutions. Five major types of structures, common to both fulvic and humic acid preparations, were observed: small discrete spheroids (9 to 50 nm in diameter); flattened aggregates of spheroids (100 to 200 nm in diameter); linear, chainlike assemblies of these larger aggregates; flattened filaments (15 to 150 nm in width); and perforated sheetlike structures. Transitional stages were noted between these various structural conformations. The concentration of the humic substance in solution at the time of freezing and drying determined the type of structure that predominated in the deposits. Varying the pH (3.5, 7.0, 10.0) of the original solutions had no effect on the type of structures observed. The techniques introduced overcome many of the difficulties inherent in the preparation of humic substances for transmission electron microscopy and have potential use in the study of metal- and clay-complexing of these materials.

Detection of nitrogen at {100} platelets in diamond

Abstract: Platelets in type Ia diamond were first directly observed with transmission electron microscopy by Evans and Phaal1 in 1962. Considerable controversy still exists over their structure and chemical composition. One of the earliest models of the platelet structure was that proposed by Lang2 in which nitrogen, the major impurity in type Ia diamonds, is segregated into plate-like structures, only two atoms thick, lying on the cube planes. Later evidence seemed to favour interstitial carbon as the major component of the platelets3–5, although more recent evidence from the production of platelets in synthetic diamond6 again points to nitrogen as forming an important constituent. High resolution electron microscopy also supports this view7,8. Here we report for the first time the direct observation of nitrogen at platelets using the technique of electron energy loss spectroscopy (EELS).

Analysis of carbides formed during accelerated aging of 2·25Cr–1Mo steel

Abstract: Power-generating plants require materials that can withstand service conditions up to 100 000 h. It is well established that creep properties are controlled by the microstructure and that the microstructure changes during creep service. Accelerated aging was used to obtain a series of simulated microstructures similar to those observed in specimens after long-time service. Electron microscopy was used to monitor the microstructural changes in the specimens. Energy-dispersive X-ray analysis was performed on carbon extraction replicas in a transmission electron microscope. The analysis was combined with an in situ electron diffraction identification of the crystal structure of the carbides present. The authors concluded that accelerated thermal aging can produce simulated service microstructures and that it is possible to distinguish between the cubic carbide M6C and M23C6 using the X-rays generated in these crystals by the electron beam. Thus a comprehensive study of carbide formation and composit...

Epitaxial regrowth of (100) InP layers amorphized by ion implantation at room temperature

Abstract: The formation and the annealing of InP amorphous layers obtained by implantation of Be (400 KeV), Cr, and Se (800 KeV) ions at room temperature are studied using Rutherford Backscattering, reflection high energy electron diffraction, transmission electron diffraction and microscopy, x‐ray diffraction techniques. The reordering of (100) InP during anneal at temperatures up to 800 °C is seen to be mainly governed by the thickness of the amorphous layer, the maximum thickness of good reepitaxy from a single crystal being limited to about 2000 A. Two cases must be considered. When the sample is amorphized up to the surface, a 2000‐A‐thick regrowth occurs from the bulk only. When a crystalline layer remains at surface, the regrowth occurs from both substrate and surface so that the total thickness of the reepitaxied layer can reach 4000 A. A schematic description of regrowth is proposed. The phenomena limiting the thickness of the reepitaxied layer and the consequences of the cold‐hammered and polycrystalline layers resulting from an incomplete regrowth are discussed.The formation and the annealing of InP amorphous layers obtained by implantation of Be (400 KeV), Cr, and Se (800 KeV) ions at room temperature are studied using Rutherford Backscattering, reflection high energy electron diffraction, transmission electron diffraction and microscopy, x‐ray diffraction techniques. The reordering of (100) InP during anneal at temperatures up to 800 °C is seen to be mainly governed by the thickness of the amorphous layer, the maximum thickness of good reepitaxy from a single crystal being limited to about 2000 A. Two cases must be considered. When the sample is amorphized up to the surface, a 2000‐A‐thick regrowth occurs from the bulk only. When a crystalline layer remains at surface, the regrowth occurs from both substrate and surface so that the total thickness of the reepitaxied layer can reach 4000 A. A schematic description of regrowth is proposed. The phenomena limiting the thickness of the reepitaxied layer and the consequences of the cold‐hammered and polycrystalline ...

Microstructure and light emission of ac thin‐film electroluminescent devices

Abstract: The microstructure of ac‐thin film electroluminescent devices was studied by transmission electron microscopy (TEM) of cross‐sectional specimens, and was correlated to electro‐optical characteristics of the devices. The cross sections reveal the microstructure of the BaTiO3/ZnS:Mn/BaTiO3 layer structure as a function of film depth. The rf‐sputtered BaTiO3 films are amorphous; the electron‐beam evaporated ZnS films are polycrystalline. The first‐to‐grow region of the ZnS layers always exhibits a very small grain size. With increasing film thickness the growth of larger columnar grains is observed. At higher substrate temperatures the grains have a more conical shape. The Mn‐concentration, measured by x‐ray microanalysis on the cross‐sectional specimens in a scanning TEM, shows an overall increase with growing ZnS film thickness, because the ZnS was evaporated from a single ZnS:Mn source. Annealing at 550 °C improves the electro‐optic characteristics of the samples considerably, without changes in microstructure being observable. Annealing at 850 °C induces strong recrystallization. The initial fine‐grained region disappears and the grains extend from the bottom to the top of the ZnS film.

A Comparative Study of Fibre Type Characteristics and Terminal Innervation in Head and Axial Muscle of the Carp (Cyprinus Carpio L.) : a Histochemical and Electron-Microscopical Study

Abstract: In the axial muscles and in a head muscle (m. hyohyoideus) of the carp two slow (red) and three fast (white, large pink and small pink) fibre types were distinguished on the basis of reactions with antisera, the pH stability of ATPase and succinatedehydrogenase activity. The gradual transition in histochemical characteristics between small and large pink fibres and the occurrence of stadia intermediate between myosatellite cells and small muscle fibres suggest that the small fibres are a growth stage. Density of nerve terminations was highest on red fibres, which is in accordance with physiological data. White axial muscle fibres had the lowest termination density. Pink fibres of the m. hyohyoideus had significantly more terminations per millimeter fibre length than pink fibres of the axial muscles. Vesicle densities per endplate profile and per synaptic contact were similar in all types. Endplates on white fibres had narrower synaptic clefts and vesicles that were slightly more elliptical than those on other types. The presence of swollen mitochondria in endplates on red head muscle fibres may reflect the continuous rhytmic activity of these fibres. The absence of subjunctional folds on slow as well as on fast fibres suggest that endplates on both types release but little acetylcholine per stimulus.

Epitaxial NiSi2 formation by pulsed ion beam annealing

Abstract: Epitaxial nickel silicide layers have been formed by ion beam annealing of 300–400‐A Ni films on (001) Si with 300–400‐ns pulses of H+ or Ba+ ions. Cellular structures were formed at an H+ energy density of 1.3 J/cm2 and a Ba+ energy density above about 0.7 J/cm2. At lower energy densities, uniform epitaxial layers of NiSi2 were formed, as indicated by both Rutherford backscattering channeling and transmission electron microscopy. With ion beam annealing, melting starts at the Ni/Si interface and epitaxy is found at energy densities well below that required to melt crystalline Si.

Scanning transmission electron microscope microanalytical study of phosphorus segregation at grain boundaries in thin‐film silicon

Abstract: Phosphorus segregation at grain boundaries in thin‐film silicon has been investigated by scanning transmission electron microscope x‐ray microanalysis. Low‐pressure chemically vapor‐deposited silicon was heavily diffusion doped and subsequently annealed at 650, 700, 750, or 800 °C. Enhanced phosphorus concentrations were observed at grain boundaries with increasing levels at lower annealing temperatures. The amount of segregation was also found to vary from boundary to boundary in each specimen. The average energy of segregation was evaluated as 7.5 kcal/mol.

TEM investigation of crystallization phenomena in the metallic glass Vitrovac? 0040 (Fe40Ni40B20)

Abstract: The crystallization behaviour of the amorphous alloy Fe40Ni40B20 was investigated by transmission electron microscopy (TEM) and light microscopy. The three different types of crystals, which occur simultaneously in the temperature range between 355 and 385‡ C, were formed by time-dependent or athermal nucleation, respectively. The number of such athermally formed nuclei increases with decreasing quench speed, whereas the time-dependent nucleation is not influenced. The linear growth of all three crystal types is likewise independent of the quenching rate. Although the activation energies for growth, Eg, are the same for all three types, there are great differences in growth rates, and therefore the thermal stability against crystallization is controlled by the fastest-growing type of crystal. Furthermore, a mechanical treatment or plastic deformation may produce surface crystallization.

Recrystallization of buried amorphous layers and associated electrical effects in P+-implanted Si

Abstract: The recrystallization behaviour of a buried amorphous layer formed by P+ implantation in (111) Si has been studied using transmission electron microscopy (TEM), secondary-ion mass spectroscopy (SIMS) and Hall measurements. Special TEM specimen preparation techniques were used to study individual sub-surface damage regions in the as-implanted as well as the annealed samples. The TEM results showed that the recrystallization of the amorphous layer began slowly, increased rapidly above 550°C and was complete at 600°C. At temperatures betweeen 750 and 1000°C, two discrete layers of interstitial a/2 ⟨110⟩ and a/3⟨111⟩ dislocation loops formed below the specimen surface, and the surface region concontained stacking-fault tetrahedra. The SIMS results showed that pronounced segregation of phosphorus atoms occurred in the defect-rich regions at 750°C. At higher annealing temperatures P segregation still occurred, but the magnitude of the segregation was reduced because of diffusive effects. The segregatio...

First and second order twin boundaries in edge defined film growth silicon ribbon

Abstract: The equilibrium defect structure of edge defined film‐fed growth ribbons consists of linear twins and twin bundles lying parallel to the growth direction. These twins show similar etching behavior in spite of the fact that their electrical activity i.e. efficiency as recombination centers, can vary greatly. Correlated electron beam induced current microscopy and high voltage transmission electron microscopy show (i) that some of the linear boundaries consist of alternating sections of coherent first order twins and incoherent second order twins of the {111}/{115} type and (ii) that the first order twins are not electrically active, whereas the second order twins act as strong recombination centers. Structural models of the {111}/{115} interface indicate a large fraction of dangling bonds. Macroscopically, the alternating sections of these twin boundaries form single straight boundaries running parallel to the growth direction of the ribbon. In etching experiments the alternating sections of boundaries des...

Structural phase transitions of indium/indium oxide thin‐film composites

Abstract: Correlation of resisitivity measurements with transmission electron microscopy analysis reveals that indium/indium oxide thin films, prepared by reactive ion‐beam sputter deposition, undergo pronounced and heretofore unrecognized structural phase transitions as a function of increasing oxide content. We have found that these films can be fabricated in a reproducible manner with microstructure characterized as either granular, with crystalline grains embedded in crystalline oxide, amorphous, or mixed amorphous and crystalline.

Evaluation of the microstructure of ß-SiAlON solid solution materials containing different amounts of amorphous grain boundary phase

Abstract: In order to test the possibility of quantitative microstructural anlaysis in Si3N4 ceramics, β solid solution materials containing different amounts of an amorphous phase were examined by transmission electron microscopy. The results show the amount and distribution of the amorphous phase and the influence of this phase on the grain morphology. This shows that within certain limits, set by the transmission electron microscopy, such a characterization is possible.

Precipitations in a Dental Ag-Pd-Cu-Au Alloy

Abstract: The structure of a dental Ag-Pd-Cu-Au alloy has been studied after centrifugal casting and various heat treatments. By transmission electron microscopy, a high density of small fct particles, assumed to be PdCu, was observed, but, in addition, finely-spaced rods of ~ 0.05 μm (500 A) diameter with an fcc structure precipitated on the {100} planes of the matrix were found. On the basis of their structure and the pertaining lattice parameter, these rods are assumed to be Cu-rich. They could also be observed by scanning electron microscopy, but not at annealing temperatures lower than 425° C.