Showing papers on "Transmission electron microscopy published in 1992"
TL;DR: In this paper, a method for attaching semiconductor nanocrystals to metal surfaces using self-assembled difunctional organic monolayers as bridge compounds is described, and three different techniques are presented.
Abstract: A method is described for attaching semiconductor nanocrystals to metal surfaces using self-assembled difunctional organic monolayers as bridge compounds. Three different techniques are presented. Two rely on the formation of self-assembled monolayers on gold and aluminum in which the exposed tail groups are thiols. When exposed to heptane solutions of cadmium-rich nanocrystals, these free thiols bind the cadmium and anchor it to the surface. The third technique attaches nanocrystals already coated with carboxylic acids to freshly cleaned aluminum. The nanocrystals, before deposition on the metals, were characterized by ultraviolet-visible spectroscopy, X-ray powder diffraction, resonance Raman scattering, transmission electron microscopy (TEM), and electron diffraction. Afterward, the nanocrystal films were characterized by resonance Raman scattering, Rutherford back scattering (RBS), contact angle measurements, and TEM. All techniques indicate the presence of quantum confined clusters on the metal surfaces with a coverage of approximately 0.5 monolayers. These samples represent the first step toward synthesis of an organized assembly of clusters as well as allow the first application of electron spectroscopies to be completed on this type of cluster. As an example of this, the first X-ray photoelectron spectra of semiconductor nanocrystals are presented. 51 refs., 17 figs.
597 citations
TL;DR: In this article, a large lattice constant on Si has been obtained by growing compositionally graded GexSi1−x on Si, and these buffer layers have been characterized with electron-beam-induced current, transmission electron microscopy and x-ray diffraction to determine the extent of relaxation, threading dislocation density, the surface morphology, and the optical properties.
Abstract: To obtain a large lattice constant on Si, we have grown compositionally graded GexSi1−x on Si. These buffer layers have been characterized with electron‐beam‐induced current, transmission electron microscopy, scanning electron microscopy, x‐ray diffraction, and photoluminescence to determine the extent of relaxation, the threading dislocation density, the surface morphology, and the optical properties. We have observed that it is possible to obtain completely relaxed GexSi1−x layers with 0.1
549 citations
TL;DR: The interaction of Cu with Si separated by thin (50 nm) layers of tantalum, Ta2N, and a nitrogen alloy of Ta has been investigated to determine the factors that affect the success of these materials as diffusion barriers to copper.
Abstract: The interaction of Cu with Si separated by thin (50 nm) layers of tantalum, Ta2N, and a nitrogen alloy of Ta has been investigated to determine the factors that affect the success of these materials as diffusion barriers to copper. Intermixing in these films was followed as a function of annealing temperature by in situ resistance measurements, Rutherford backscattering spectra, scanning electron microscopy, and cross‐section transmission electron microscopy. Ta prevents Cu‐silicon interaction up to 550 °C for 30 min in flowing purified He. At higher temperatures, copper penetration results in the formation of η‘‐Cu3Si precipitates at the Ta‐Si interface. Local defect sites appear on the surface of the sample in the early stages of this reaction. The Ta subsequently reacts with the substrate at 650 °C to form a planar hexagonal‐TaSi2 layer. Ta silicide formation, which does not occur until 700 °C in a Ta‐Si binary reaction couple, is accelerated by the presence of Cu. Nitrogen‐alloyed Ta is a very similar...
422 citations
Book•
01 Jan 1992
TL;DR: In this article, the properties and properties of frozen water and aqueous solutions are discussed. But the authors focus on the properties of water and do not discuss the structure of water.
Abstract: The Properties and Structure of Water. The Structure and Properties of Frozen Water and Aqueous Solutions. Sample Cooling Proceedures. Cryosectioning. Low Temperature Fracturing and Freeze Fracture Replication. Freeze Drying. Freeze Substitution and Low Temperature Embedding. Low Temperature Light Microscopy. Low Temperature Transmission Electron Microscopy. Low Temperature Scanning Electron Microscopy. Low Temperature Microanalysis. Index.
324 citations
Book•
01 Jan 1992
323 citations
TL;DR: In this article, the silicide-mediated phase transformation of amorphous to crystalline silicon was observed in situ in the transmission electron microscope, and a diffusion-controlled mechanism for the enhanced crystallization rate was determined.
Abstract: The silicide‐mediated phase transformation of amorphous to crystalline silicon was observed in situ in the transmission electron microscope. Crystallization of nickel‐implanted amorphous silicon occurred at ∼500 °C. Nickel disilicide precipitates were observed to migrate through an amorphous Si film leaving a trail of crystalline Si. Growth occurred parallel to 〈111〉 directions. High resolution electron microscopy revealed an epitaxial NiSi2/Si(111) interface which was Type A. A diffusion‐controlled mechanism for the enhanced crystallization rate was determined.
254 citations
TL;DR: In this article, the formation mechanisms and properties of TiSi2 on Si are investigated and the particular emphasis is in relating the nucleation, morphology, and phase stability of the films.
Abstract: The formation mechanisms and properties of TiSi2 on Si are investigated. The particular emphasis is in relating the nucleation, morphology, and phase stability of the films. TiSi2 films were prepared by deposition of Ti on atomically clean silicon substrates in ultrahigh vacuum. The silicide formation was initiated either by in situ annealing or deposition onto heated substrates. The island formation of TiSi2 and surface and interface morphologies of TiSi2 were examined by scanning electron microscopy and transmission electron microscopy. The TiSi2 formation process was monitored with in situ Auger electron spectroscopy and low‐energy electron diffraction to analyze the surface concentration and the surface structures, respectively. Raman spectroscopy was used for phase identification of the TiSi2. Titanium film thicknesses from 50 to 400 A were examined. For all thicknesses studied, the C49 TiSi2 phase is observed to nucleate. Immediately after low‐temperature deposition, the interface morphology was smo...
219 citations
TL;DR: Gold sputtering produces pebble-type structures with very small grains and no crystallographic texture, while evaporation of gold onto glass or mica produces large, flat crystallites, with a pronounced {111} texture.
171 citations
TL;DR: The bonding strength was considered to be mainly attributable to mechanical interlocking, and the surfaces of the implants became rough due to degradation, and bone grew into the finest surface irregularities.
Abstract: The interface between bioactive ceramics and bone was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The materials were apatite-wollastonite-containing glass ceramic (A-W.GC) as a representative surface-active ceramic, and calcite and beta-tricalcium phosphate (beta-TCP) as resorbable ceramics. Particles of these materials, ranging between about 100 microns and 300 microns in diameter, were implanted into rat tibiae, and specimens were prepared for observation at 8 weeks after implantation. Both SEM and TEM demonstrated that A-W.GC was bonded to bone through a thin Ca-P-rich layer consisting of fine apatite crystals apparently different from those of bone in shape, size, and orientation. Collagen fibers of the bone reached the surface of this layer, and chemical bonding between A-W.GC and the bone was speculated. Calcite and beta-TCP, on the other hand, made direct contact with the bone, and no apatite layer was present at the interface. The surfaces of the implants became rough due to degradation, and bone grew into the finest surface irregularities. However, we were unable to demonstrate any continuity of crystals between the resorbable implants and bone by high-resolution TEM. Accordingly, the bonding strength was considered to be mainly attributable to mechanical interlocking.
155 citations
TL;DR: In this article, a diamond phase carbon film was grown on silicon substrates at temperatures of less than 50°C by using an organic solution, which was negatively biased with sufficient dc potential to simulate ionized deposition conditions used in physical vapor deposition.
Abstract: Diamond phase carbon films have been grown on silicon substrates at temperatures of less than 50 °C by using an organic solution. Substrates were negatively biased with sufficient dc potential to simulate ionized deposition conditions used in physical vapor deposition. The surface morphology, crystal structure, and some physical properties of the films were examined by scanning electron microscopy, transmission electron microscopy, x‐ray photoemission spectroscopy. It was confirmed that the film is composed of small grains of diamond phase or diamondlike structure.
150 citations
TL;DR: In this paper, it was shown that crystalline Si (c-Si) nucleates within the Al layers and penetrates the Al as the c-Si grows, and the overall activation energy of the reaction, determined by calorimetry, is 1·2 ± 1 eV.
Abstract: The crystallization of amorphous Si (a-Si) in Al/a-Si multilayer thin films has been investigated by ex situ and in situ transmission electron microscopy (TEM), X-ray diffraction and calorimetry. The a-Si crystallizes at about 200°C, a significantly lower temperature than for the pure elemental state, with a heat of crystallization of about 12 kJ (mol Si)−1. We show that crystalline Si (c-Si) nucleates within the Al layers and penetrates the Al as the c-Si grows. The speed of the growth of c-Si observed by in situ TEM was a few angstroms per second at 220°C. Al grains are separated and the layered structure is destroyed, while the Al(111) film texture is enhanced. The overall activation energy of the reaction, determined by calorimetry, is 1·2 ± 01 eV. We propose a model in which diffusion of Si through the Al grains and rearrangement of the Al grains occur simultaneously.
TL;DR: In this article, arachidic acid (AA)-monolayer-coated aqueous lead nitrate [Pb(NO 3 ) 2 ] solutions to hydrogen sulfide (H 2 S) were transferred to solid substrates and characterized by transmission electron microscopy, atomic force microscopy (AFM), and electron diffraction measurements.
Abstract: Lead sulfide (PbS) particulate films composed of highly oriented, equilateral-triangular crystals have been in situ generated by the exposure of arachidic acid (AA)-monolayer-coated aqueous lead nitrate [Pb(NO 3 ) 2 ] solutions to hydrogen sulfide (H 2 S). The AA-coated PbS particulate films, at different stage in their growth, were transferred to solid substrates and characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), and electron diffraction measurements
TL;DR: In this article, a number of bulk (manometric hydrogen content measurements, optical microscopy), structural (X-ray and neutron diffraction) and microstructural (scanning and transmission electron microscopy) techniques provide strong evidence that the major part of the observed reduction in hysteresis after activation is due to the formation of extended two-dimensional defects in the alloy.
TL;DR: In this article, the authors showed that carbon nitride in amorphous and crystalline forms can be synthesized using reactive magnetron sputtering with substrates held at ambient temperatures.
Abstract: Our preliminary studies showed that carbon nitride in amorphous and crystalline forms can be synthesized using reactive magnetron sputtering with substrates held at ambient temperatures The films were evaluated by a wide range of diagnostic techniques (Auger spectroscopy, IR spectroscopy, scanning electron microscopy, energy-dispersive X-ray analysis, atomic force microscopy, transmission electron microscopy and tribo-testing) The most important finding is that we can deposit smooth, continuous C-N films on a variety of substrates Unlike previous work, we were able to incorporate significant amounts of nitrogen into these films (N:C ratio exceeding 04 in the bulk) More importantly, IR studies show that nitrogen exists not merely as gaseous species but is chemically bonded to carbon in the film Transmission electron microscopy studies showed clearly the coexistence of amorphous and crystalline C-N phases When deposited on polycrystalline zirconium substrates, these films appear to be very adherent and wear resistant under lubricated sliding conditions In dry sliding against 52100 steels, carbon nitride gives friction coefficients as low as 016, comparable with that of diamond
TL;DR: In this paper, several examples for the application of electron channelling contrast as a means for investigating the microstructure of metals after deformation are given, including the change in dislocation glide mechanism during fatigue of the austenitic stainless steel AISI 304L as a function of deformation temperature.
Abstract: Electron channelling contrast is obtained in the scanning electron microscope by detecting back-scattered electrons created by a parallel incident electron beam. The intensity of the back-scattered electrons depends on the orientation of the incident beam with respect to the crystal lattice. In this report, several examples for the application of channelling contrast as a means for investigating the microstructure of metals after deformation are given. First, the change in dislocation glide mechanism during fatigue of the austenitic stainless steel AISI 304L as a function of deformation temperature is demonstrated by means of a comparative study by transmission electron microscopy and scanning electron microscopy (SEM) channelling contrast. The efficiency of channelling contrast in imaging dislocation arrangements is shown. In the next example, referring also to AISI 304L, it is shown that electron channelling contrast can also be applied advantageously to the study of subgrain structures in the ...
TL;DR: The structural and morphological characteristics of visible-light-emitting porous Si layers produced by anodic and stain etching of single-crystal Si substrates are compared using transmission electron microscopy and atomic force microscopy (AFM) as discussed by the authors.
Abstract: The structural and morphological characteristics of visible-light-emitting porous Si layers produced by anodic and stain etching of single-crystal Si substrates are compared using transmission electron microscopy and atomic force microscopy (AFM). AFM of conventionally anodized, laterally anodized and stain-etched Si layers show that the layers have a fractal-type surface morphology. The anodized layers are rougher than the stain-etched films. At higher magnification 10 nm sized hillocks are visible on the surface. Transmission electron diffraction patterns indicate an amorphous structure with no evidence for the presence of crystalline Si in the near-surface regions of the porous Si layers.
TL;DR: In this article, the structures of physical-vapourdeposited magnesium, lanthanum, calcium and lithium fluoride films were investigated using transmission electron microscopy microfractographical replication and diffraction techniques, secondary neutral mass spectrometry, depth profiles and packing density measurements.
TL;DR: In this paper, the phase formation in the interfacial reactions of ultrahigh vacuum deposited Ti thin films on (111)Si has been studied by in situ reflected high energy electron diffraction (RHEED) and transmission electron microscopy (TEM).
Abstract: Phase formation in the interfacial reactions of ultrahigh vacuum deposited Ti thin films on (111)Si has been studied by in situ reflected high energy electron diffraction (RHEED) and transmission electron microscopy (TEM). In situ RHEED and high resolution TEM data showed unambiguously that there is considerable intermixing of Ti and Si atoms during Ti deposition. Ti5Si3 was found to be the first nucleated phase followed by Ti5Si4 and TiSi. Ti5Si3, Ti5Si4, TiSi, and C49‐TiSi2 along with a‐interlayer were found to form in samples annealed at 475 °C for 30 and 60 min. Ti5Si4 was the first silicide phase to disappear followed by Ti5Si3 then TiSi. In samples annealed at 700 °C for 10 min, C54‐TiSi2 started to appear. To understand the thermodynamic origin of the phase formation, metastable free energy diagrams at 450–600 °C have been constructed. Ti5Si3 and C49‐TiSi2 were found to have the highest and lowest driving force, respectively. On the other hand, Ti5Si4 has the lowest interface energy. The sequence o...
TL;DR: In this article, a novel transmission electron microscopy technique was developed to monitor the oxidation progress without removing the oxide structural support, and the oxidation rates of the Si nanostructures were characterized.
Abstract: Understanding the optical and electrical properties of Si nanostructures is essential for exploring the potential of using structural quantum confinement to induce light emission from crystalline Si. To this end, sub‐50 nm Si columns were fabricated with high resolution electron beam lithography and anisotropic reactive ion etching. The dimensions of the Si nanostructures were further reduced by thermal oxidation. A novel transmission electron microscopy technique was developed to monitor the oxidation progress without removing the oxide structural support. Images of sub‐5 nm crystalline Si cores were obtained. The oxidation rates of the Si nanostructures were characterized. Among the various interesting oxidation phenomena are the nonmonotonic oxidation rate with respect to the column size and an unexpectedly slow change of the outer diameters of the oxidized columns. Several likely mechanisms, including the stress retardation of oxidation for a small radius of curvature, the stress induced generation an...
TL;DR: In this paper, the stoichiometry, crystallinity, defect concentration, and the excess As lattice location in GaAs layers grown by molecular beam epitaxy at low growth temperatures (≤300 C) were studied using ion beam techniques.
Abstract: The stoichiometry, crystallinity, defect concentration, and the excess As lattice location in GaAs layers grown by molecular beam epitaxy at low growth temperatures (≤300 °C) were studied using ion beam techniques. The excess As concentration in the layers was measured by particle induced x‐ray emission and was found to increase as the growth temperature was lowered. Excess As concentrations up to 1.5 at. % were measured in layers grown at 190 °C. After annealing at temperatures higher than 400 °C under As overpressure, the excess As atoms coalesce to form As precipitates as revealed by transmission electron microscopy. Ion channeling on the unannealed layers grown at 200 °C revealed that they have good crystalline quality with a large fraction of the excess As atoms sitting at interstitial sites close to the normal As sites in the lattice. The rest of the excess As atoms are believed to be in an AsGa antisite position.
TL;DR: In this paper, a systematic study of the growth of high-quality films of GaAs on Si substrates has been performed for applications in devices, particularly in optoelectronic devices for cointegration in optical interconnects.
Abstract: A systematic study of the growth of high‐quality films of GaAs on Si substrates has been performed for applications in devices, particularly in optoelectronic devices for cointegration in optical interconnects. The effort for optimized active layers was approached through the separate optimization of substrate preparation, growth time parameters, and postgrowth treatment. In particular, the study of growth involved the investigation of the effect of silicon substrate orientation, post‐growth treatment, as well as multilayer and, especially, silicon buffer layers. For quantification of film quality, a number of characterization methods were used both in situ: reflected high‐energy electron diffraction (RHEED); and ex situ: optical, electrical [current versus voltage (I‐V), capacitance versus voltage (C‐V), deep‐level transient spectroscopy (DLTS), Hall], transmission electron microscopy (TEM), scanning electron microscopy (SEM), electron channeling patterns, x‐ray double‐crystal diffractometry (DDX). Schot...
TL;DR: The role of initial size and morphology in the thermal evolution is fundamental: very fine spherical particles (0.01-0.02 μm), can be sintered to give particles of 0.1 − 0.3 μm at 875 °C with unchanged morphology as discussed by the authors.
Abstract: Spherical ZnO microcrystals obtained by spray pyrolysis and thermal decomposition methods as well as rod-like ZnO particles (prismatic and needle shaped) prepared from precipitation in aqueous solutions, have been characterized by electron microscopy, X-ray diffraction and infrared spectroscopy. Very different sizes of ZnO particles were obtained from spray pyrolysis. However, only the larger particles (0.7 μm) were found to be slightly deformed by infrared spectroscopy. From thermal decomposition of zinc acetate, fine particles of average size 0.05 μm, rather spherical and agglomeration free were obtained. The role of initial size and morphology in the thermal evolution is fundamental: very fine spherical particles (0.01–0.02 μm), can be sintered to give particles of 0.1–0.3 μm at 875 °C with unchanged morphology. When the temperature induces a change in spherical shape, the first microstructural changes appear to take place through the crystallographic c-axis. However, for rod-like particles, changes begin from the a, b axes, being faster for needle-shaped microcrystals.
15 Oct 1992-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, two titanium alloys with 24 and 50 at% Al were mechanically alloyed in a steel vial with hardened steel balls using a Spex 8000 mixer-mill.
Abstract: Two titanium alloys with 24 and 50 at% Al respectively, were mechanically alloyed in a steel vial with hardened steel balls using a Spex 8000 mixer-mill The sequence of phases formed has been investigated by both X-ray diffraction and transmission electron microscopy With increasing milling time a solid solution of aluminum in titanium, intermetallic Ti 3 Al, an amorphous phase and an fcc crystalline phase formed sequentially The formation of the amorphous phase has been rationalized in terms of Miedema's thermodynamic analysis The results available on the fcc phase suggest that this phase may be a titanium nitride formed by pick-up of nitrogen during milling and that it has not formed by the crystallization of the amorphous phase per se
TL;DR: In this article, a high energetic ball mill under nitrogen gas flow at room temperature was used to fabricate nonequilibrium titanium-nitride alloy powders, which were characterized by means of x-ray diffraction, scanning electron microscopy, transmission electron microscope, and differential scanning calorimetry.
Abstract: Nonequilibrium titanium-nitride alloy powders have been fabricated by a high energetic ball mill under nitrogen gas flow at room temperature and characterized by means of x-ray diffraction, scanning electron microscopy, transmission electron microscopy, and differential scanning calorimetry. Initial hcp titanium is completely transformed to nonequilibrium-fcc Ti–N after 720 ks of the milling time. The fcc Ti–N phase is stable at relatively low temperature and transforms at 855 K to Ti2N and δ phases. At the final stage of milling, the particle- and grain-sizes of alloy powders are 1 mm and 5 nm, respectively, and the lattice parameter is 0.419 nm.
TL;DR: In this article, the erbium is incorporated primarily as near spherical micro-precipitates which possess a cubic (rocksalt) structure consistent with their chemical composition being ErAs.
TL;DR: In this paper, a method for microfabrication of three-dimensional structures in free space is presented, where a laser-assisted chemical vapor deposition is used to grow a material at a point where the laser beam locally heats the substrate.
Abstract: A method for microfabrication of three‐dimensional structures in free space is presented. Laser‐assisted chemical vapor deposition is used to grow a material at a point where a laser beam locally heats the substrate. By moving the substrate relative to the laser beam with a micropositioning system, three‐dimensional shapes can be created. Helical shapes are generated utilizing three linear translational axes as well as an additional rotational axis. Tilting the substrate to align the growth direction with the laser beam direction facilitates improved process control. The smallest structures that can be grown with this technique are about 1 μm. Amorphous boron fibers and crystalline boron springs have been manufactured as two examples of micromechanical elements. The amorphous boron fibers show excellent mechanical properties: A modulus of elasticity of 420–450 GPa, a fracture strain of 2.7%–3.7%, and a fracture stress of 12–17 GPa. The crystalline boron springs produced so far display only moderate mechanical characteristics. This is because of the irregular fiber surface with protruding grains and amorphous nodules. Nevertheless, a maximum relative resilience of about 9% for a tightly wound spring has been obtained. The crystal structure of the grains examined show a fair agreement with the β‐boron phase, even though distinct deviations are observed. Metastable arrangement of the B12 icosahedral units is suggested as a possible explanation. A high density of (100) twins and stacking faults are identified by transmission electron microscopy. By further process and system development it is believed that micromechanical details can be tailored more or less arbitrarily for different applications.
TL;DR: In this article, various spectra of Raman for different grain sizes of diamond powder have been studied and correlated to the results of transmission electron diffraction, transmission electron microscopy, scanning electron microscope, and x-ray photoelectron spectroscopy.
Abstract: Various spectra of Raman for different grain sizes of diamond powder have been studied. The spectra are also correlated to the results of transmission electron diffraction, transmission electron microscopy, scanning electron microscopy, and x‐ray photoelectron spectroscopy. When the Raman peak intensity was decreased, the spectra broadened and shifted to a lower frequency in accordance with the decrease of the grain size. Finally, in the region of a few hundred angstroms, the detected signals were almost comparable to the noise level. While unchanged, lattice spacings for transmission electron diffraction patterns and constant peak heights for x‐ray photoelectron spectroscopy analysis were observed for different grain sizes.
IBM1
TL;DR: In this paper, transmission electron microscopy was used to analyze the effects of annealing treatments on the morphologies of discontinuous gold films evaporated onto polystyrene or poly(2-vinylpyridine) substrates.
Abstract: Transmission electron microscopy was used to analyze the effects of annealing treatments on the morphologies of discontinuous gold films evaporated onto polystyrene or poly(2‐vinylpyridine) substrates. For polystyrene substrates the average size of discrete gold particles increases significantly during a long‐term annealing treatment at 179 °C. The size distribution is well approximated by a log normal distribution function, consistent with a coalescence mechanism for particle growth. The fluid character of the polymer substrates at the annealing temperature of interest allows us to control this coalescence rate, thereby providing a unique method for controlling the microstructure of discontinuous metal films. Cross‐sectional transmission electron microscopy showed that the coalescence rate for gold particles in a poly(2‐vinylpyridine) matrix is much less than the coalescence rate for gold particles in a polystyrene matrix, indicating that polymer/metal interactions play an important role in the determina...