Showing papers on "Transmission electron microscopy published in 1978"

Impurity Phases in Hot-Pressed Si3N4

Abstract: Impurity phases in commercial hot-pressed Si3N4 were investigated using transmission electron microscopy. In addition to the dominant, β-Si3N4 phase, small amounts of Si2N2O, SiC, and WC were found. Significantly, a continuous grain-boundary phase was observed in the ∼ 25 high-angle boundaries examined. This film is ∼ 10 A thick between, β-Si3N4 grains and ∼ 30 A thick between Si2N2O and β-Si3N4 grains.

Studies of thermally-oxidized GaAs by transmission electron microscopy

Abstract: Thermally oxidized GaAs has been examined using transmission electron microscopy to determine the structure and phases of the resulting oxide films. At growth temperatures of 500°C and above, the films were composed mainly of twinned poly-crystalline β-Ga 2 O 3 , the amount of crystallinity increasing with growth temperature. An amorphous oxide film was formed at a low growth temperature (450°C). No arsenic-containing phases were detected in any oxide film.

Reaction kinetics of molybdenum thin films on silicon (111) surface

Abstract: Silicon‐metal systems are highly susceptible to solid‐solid reactions which modify their electrical and mechanical properties. Although many works are dealing with silicide formation, the molybdenum‐silicon system has not yet been investigated in detail to our knowledge. In this paper we present a He+ ion backscattering study of the molybdenum‐silicide formation by interaction of a thin molybdenum layer and a silicon 〈111〉 wafer. The silicide phases Mo3Si and MoSi2 have been identified by x‐ray diffraction and transmission electron microscopy. Surface transformations were observed by scanning electron microscopy. For an 800‐A Mo layer sputter deposited on silicon, we have found a time‐square growth rate for MoSi2 with an average activation energy of 2.4 eV in the temperature range 475–550 °C. The fundamental roles of the cleaning of the silicon surface, of the substrate temperature during sputtering, and of the stresses in the layer are pointed out.

Low temperature scanning electron microscopy: a review.

Abstract: Low temperature scanning electron microscopy is useful for morphological and analytical studies both in situations where low temperature techniques are used during specimen preparation and where low temperature stages are used for specimen examination and analysis. Examples are given of different low temperature specimen preparation techniques and how they may be applied to different types of specimen. There are still a number of problems associated with morphological identification in fully frozen-hydrated samples and it is important to carry out parallel studies using more conventional transmission electron microscopy and light microscopy preparation techniques. A number of criteria are presented, some or all of which may be used to establish the existence of the frozen-hydrated state.

Lamellation in the S2 layer of softwood tracheids as demonstrated by scanning transmission electron microscopy

Abstract: Ultrathin cross sections of the tracheid wall in black spruce and silver fir have been examined at high resolution by scanning transmission electron microscopy (STEM) and by conventional transmission electron microscopy (TEM). For both softwoods, lamellation of the S2 layer was evident but the lamellae were seen more clearly in the STEM photomicrographs. The interlamellar distance was 7.1 nm in the case of spruce and 8.4 nm for silver fir.

An electron microscopy study of defect structures in recrystallized amorphous layers of self-ion-irradiated 〈111〉 silicon

Abstract: The defect structures remaining in a recrystallized amorphous layer of self-ion-irradiated 〈111〉 silicon have been examined by transmission electron microscopy. This study was performed in collaboration with an investigation by nuclear back-scattering-dachannelling techniques, and these results are reported in a companion paper. The residual defect microstructure for all three annealing treatments was dominated by regions twinned about the three {111} planes inclined to the (111) substrate. The volume occupied by these twins was about 30-40%. The regrowth of the amorphous layer could be subdivided into two depth zones, one near the substrate interface with a high density of small twins and another extending to the surface with a low density of large twins. Twins formed about the (111) plane parallel to the surface did not have a significant role except at the highest temperature of annealing, namely 950°C. In this case the volume occupied by these twins appeared to be much the same as for any one...

A high resolution transmission electron microscope study of early stage precipitation on dislocation lines in Al-Zn-Mg

Abstract: The weak beam transmission electron microscopy technique was employed to study the early stages of precipitation on dislocation lines in Al-3.87 wt pct Zn-1.79 wt pct Mg. The heterogeneous precipitation sequence was found to follow the homogeneous sequence in this alloy. The interaction between the initial coherent precipitate particles and the strain fields of the catalyzing dislocations produced “gaps” of background intensity at precipitate locations along the otherwise continuous weak beam images of the dislocation lines. A simple model was developed to relate a distribution of measured weak beam gap lengths to a particle size distribution at a given aging treatment. In this manner the growth kinetics of the initial precipitate phase was observed; it was found that the precipitation followed the Cottrell-Bilbyt 2/3law, suggesting that matrix dislocations may assist the growth of heterogeneous precipitates in a manner analogous to grain boundary “collector plates.” Weak beam microscopy was found to be superior to standard bright field microscopy for the current study. Particles too small to be visible in bright field were revealed in weak beam. Weak beam observations also indicated that the coherent precipitate particles were positioned asymmetrically about the dislocation cores.

Bovine Olfactory and Nasal Respiratory Epithelium Surfaces High-Voltage and Scanning Electron Microscopy, and Cryo-Ultramicrotomy

Abstract: High-voltage transmission electron microscopy and cryo-ultramicrotomy together with scanning electron microscopy and some conventional transmission electron microscopy of ultrathin sections have been applied to the mucous surfaces of bovine olfactory and respiratory epithelia. Distal segments of olfactory cilia tend to run in parallel and could be followed over distances up to about 30 μm using high-voltage electron microscopy. This technique and scanning electron microscopy showed that on average 12–13 of such cilia could be observed per nerve ending. After correction for obscured cilia this number becomes about 17. High-voltage micrographs and micrographs made from sections prepared with a cryo-ultramicrotome showed the presence of electron-lucent pockets inside the olfactory mucus. The latter technique also showed that the mucus itself is not fibrous, but rather a continuum varying in electron density. The mucus layer contains various granular structures. Ciliary and microvillar membranes appear thicker with cryo-ultramicrotomy than when the sections are prepared with conventional techniques. The cores of the axonemal microtubules in olfactory as well as in respiratory cilia are darkly stained with this technique. Vesicles present inside the nerve endings are also darkly stained. Dimensions and some other numerical values of interest in olfaction are presented.

Microstructure of SiC Prepared by Chemical Vapor Deposition

Abstract: Silicon carbide prepared by chemical vapor deposition at a substrate temperature of ∼1400425-429°C was investigated. Optical microscopy showed that the growth characteristic is dendritic; the deposits consist of columnar blocks within each of which the orientation of crystals is approximately the same. Small pores occur along the boundaries of these blocks. Transmission electron microscopy revealed finer details of the growth characteristics. The crystals were mostly 3C in structure, but crystals with 2H and one-dimensionally-disordered structures were also found. The 3C crystals are mostly dendritic, but some columnar growth with alternating twin bands occurs. Both 2H and one-dimensionallydisordered crystals exhibit a columnar habit, reflecting the difference in crystal symmetry from 3C. In all these crystals, the c axis (or one of the axes in 3C crystals) lies perpendicular to the substrate.

Structure and morphology of an age-hardened goldcopper-silver dental alloy

Abstract: Transmission electron microscopy and electron diffraction studies have been carried out in order to make clear the correlation between the microstructure and age-hardening of a dental gold alloy Au-43.2 at.% Cu13.8 at.% Ag. At lower ageing temperatures the hardening is due to the development of a long period antiphase domain structure of the AuCu-II type. The strain field induced by the AuCu-I type superlattice coexisting with the AuCu-II type superlattice also contributes to the. age-hardening. An alternating coarse lamellar structure is formed by the mechanism of discontinuous decomposition at higher ageing temperatures. The phases composing this structure have been identified as the copper-rich α 1 phase and the silver-rich α 2 phase, which are both f.c.c. in structure. No age-hardening was observed in this temperature range. In the middle temperature range (350–400 °C) the α 1 phase becomes ordered, resulting in the AuCu-II structure type, but remains intact within the lamellae. The increase in hardness on ordering is related to the volume fraction of the ordered phase.

Properties investigation of thin silicon nitride layers synthesized by ion implantation

Abstract: Structure and phase transformations of Si irradiated by nitrogen ions of 60 keV with doses from 5 × 1015 ions.cm−2 to 6 × 1017 ions.cm−2, and ion current density 20 μA cm−2 have been studied by transmission electron microscopy and ir absorption techniques. The samples were annealed in vacuum from 600°C to 1100°C.

Ion Beam Technology Applied to Electron Microscopy

Abstract: Publisher Summary Ion erosion has proved to be an increasingly valuable tool to electron microscopists, especially those engaged in examining the classes of materials, such as ceramics, composites, impurity-doped semiconductors, and alloys. These materials are difficult to etch chemically or can contain constituents that etch at widely differing rates. For specimen preparation for electron microscopy, the ion source is used as a machining tool. Where chemical or electrolytic etching is possible, liquid techniques are still favored because the equipment is generally less costly, the etching rate is faster, and there is no radiation damage; although specimens may suffer chemical contamination. Because of the relatively slow ion-etching rates, materials are commonly prethinned by mechanical or chemical means, or a combination. This chapter discusses the production of ion beams, the sputtering process, some ion etching rates and sputtering yield data, ion thinning for transmission electron microscopy, ion erosion equipment characteristics, and ion erosion for scanning electron microscopy.

Investigation of solid–solid reactions of Au films on silicon

Abstract: : Investigations were conducted on solid-solid reactions in gold films evaporated on silicon substrates at deposition temperatures below the eutectic point (370 C). Both air- and vacuum-annealed structures were studied using correlated data from transmission electron microscopy/diffraction (TEM/TED), Auger electron spectroscopy (AES) profiling, and forward current-voltage (I-V) measurements. Results of these experiments show that the grain size in Au films deposited (or annealed) at temperatures from 25 C to 200 C increases from 50 anstrom (min) to saturation size of approximately 1 micro m at temperatures greater than 150 C.

Transmission electron microscope studies on Li-doped MgO

Abstract: Transmission electron microscope investigations of as-grown Li-doped MgO have revealed the presence of precipitates with an average size of 220 A. Detailed micro-diffraction studies and moire pattern analyses have identified these precipitates as Li2O with the cubic fluorite structure. Exposures of Li-doped MgO crystals either to high temperatures in air for 10 min followed by quenching or to a large dose of ionizing radiation at ambient temperature leads to a reduction in the precipitate size. These results lend support to our previous conjecture from optical and magnetic resonance studies that localized lithium-rich environments are responsible for the stable [Li]0 centres and that the source of these lithium ions are the precipitates.

Plasma-deposited polymer films. I. Low-angle x-ray study

Abstract: A low-angle x-ray scattering technique has been applied to determine the submicrostructure of plasma-formed polyethylene and polystyrene. The plasma-formed polymers appear to closely approximate a “filler—binder” structure where polymer spheres constitute the filler material and a lower-density polymer, the binder. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) micrographs confirm the spherical diameters predicted by the low-angle x-ray scattering data.

Sizing of phosphatidylcholine vesicles by transmission electron microscopy

Abstract: SUMMARY Coating of support films for transmission electron microscopy with silica by evaporation of ‘silicon monoxide’ provides a surface which is easily wetted by aqueous systems. Dispersed colloidal particles spread on this surface without the use of added soluble wetting agents. Such coated supports are found to be particularly useful for the quantitative characterization of the size distribution of vesicles prepared from saturated phosphatidylcholine. The weight average vesicle sizes determined for several samples from measurements of negatively stained electron micrographs are in good agreement with values measured by light scattering and ultracentrifugation.