Quantum-Sized Silicon Precipitates in Silicon-Implanted and Pulse-Annealed Silicon Dioxide Films: Photoluminescence and Structural Transformations

1996 ◽  
Vol 438 ◽  
Author(s):  
I. E. Tyschenko ◽  
G. A. Kachurin ◽  
K. S. Zhuravlev ◽  
N. A. Pazdnikov ◽  
V. A. Volodin ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Silicon Dioxide ◽  
Near Infrared ◽  
Light Emission ◽  
High Resolution Electron Microscopy ◽  
Structural Transformations ◽  
Light Sources ◽  
Furnace Annealing ◽  
Si Nanocrystals ◽  
Resolution Electron

AbstractStrong blue, red and near-infrared photoluminescence has been observed from Si+-implanted and pulse-annealed SiO2 layers. Raman scattering and high-resolution electron microscopy analyses have revealed a correlation between the structure of the Si inclusions in the SiO2 matrix and the photoluminescence. Structural transformations in the Si-rich SiO2 layers during pulse and furnace annealing have been discussed in terms of the changes in the light emission observed experimentally. Small Si clusters, non-crystalline inclusions and nanocrystals are believed to be the light sources. The blue, red and near-infrared photoluminescence is associated with small complexes of excess Si atoms, non-crystalline Si nanoinclusions and quantum-confined Si nanocrystals, respectively.

Structural Transformation of a Germanium Σ=13 (510) [001] Tilt Grain Boundary under the Electron Beam

1990 ◽  
Vol 48 (1) ◽  
pp. 52-53 ◽  
Author(s):  
Jean-Luc Rouvière ◽  
Alain Bourret
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Grain Boundary ◽  
Structural Transformation ◽  
Mirror Symmetry ◽  
High Resolution Electron Microscopy ◽  
Structural Transformations ◽  
Covalent Bonds ◽  
Resolution Electron ◽  
Tilt Grain Boundary

The possible structural transformations during the sample preparations and the sample observations are important issues in electron microscopy. Several publications of High Resolution Electron Microscopy (HREM) have reported that structural transformations and evaporation of the thin parts of a specimen could happen in the microscope. Diffusion and preferential etchings could also occur during the sample preparation.Here we report a structural transformation of a germanium Σ=13 (510) [001] tilt grain boundary that occurred in a medium-voltage electron microscopy (JEOL 400KV).Among the different (001) tilt grain boundaries whose atomic structures were entirely determined by High Resolution Electron Microscopy (Σ = 5(310), Σ = 13 (320), Σ = 13 (510), Σ = 65 (1130), Σ = 25 (710) and Σ = 41 (910), the Σ = 13 (510) interface is the most interesting. It exhibits two kinds of structures. One of them, the M-structure, has tetracoordinated covalent bonds and is periodic (fig. 1). The other, the U-structure, is also tetracoordinated but is not strictly periodic (fig. 2). It is composed of a periodically repeated constant part that separates variable cores where some atoms can have several stable positions. The M-structure has a mirror glide symmetry. At Scherzer defocus, its HREM images have characteristic groups of three big white dots that are distributed on alternatively facing right and left arcs (fig. 1). The (001) projection of the U-structure has an apparent mirror symmetry, the portions of good coincidence zones (“perfect crystal structure”) regularly separate the variable cores regions (fig. 2).

Correlation between Structural and Optical Properties of Si Nanocrystals in SiO2: Model for the Visible Light Emission

2000 ◽  
Vol 650 ◽  
Author(s):  
M. López ◽  
B. Garrido ◽  
O. González ◽  
C. García ◽  
A. Pérez-Rodríguez ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Optical Properties ◽  
Band Gap ◽  
Crystallite Size ◽  
Light Emission ◽  
Stokes Shift ◽  
High Resolution Electron Microscopy ◽  
Dark Field ◽  
Structural And Optical Properties ◽  
Si Nanocrystals

ABSTRACTThe correlation between the structural and optical properties of Si nanocrystals embedded in SiO2 is the key factor to understand their emission mechanism. However, there is a great difficulty in imaging Si nanocrystals in SiO2 and measuring their size distribution because of the lack of contrast in electron microscopy. We have used here a new method for imaging Si nanocrystals by using high resolution electron microscopy in conjunction with conventional electron microscopy in dark field conditions. Regarding the optical properties, the band-gap energies and photoluminescence have been measured by direct and independent methods. The results have allowed experimental determination, for the first time in this material, of the experimental Stokes shift between absorption and emission as a function of crystallite size. The experimental band-gap versus size correlates well with the most accurate theoretical predictions. Moreover, the photoluminescence energy emission versus crystallite size shows a parallel behaviour to that of band-gap energy. Consequently, the experimental Stokes shift is independent of nanocrystal size and is found to be 0.26±0.03 eV. This value is almost twice the energy of the Si-O vibration (0.134 eV). These results suggest that the dominant emission of Si nanocrystals passivated with SiO2 is a fundamental transition spatially located at the Si-SiO2 interface and with the assistance of a local Si-O vibration.

Correlation between Structural and Optical Properties of Si Nanocrystals in SiO2: Model for the Visible Light Emission

2000 ◽  
Vol 647 ◽  
Author(s):  
M. López ◽  
B. Garrido ◽  
O. González ◽  
C. García ◽  
A. Pérez-Rodríguez ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Optical Properties ◽  
Band Gap ◽  
Crystallite Size ◽  
Light Emission ◽  
Stokes Shift ◽  
High Resolution Electron Microscopy ◽  
Dark Field ◽  
Structural And Optical Properties ◽  
Si Nanocrystals

AbstractThe correlation between the structural and optical properties of Si nanocrystals embedded in SiO2 is the key factor to understand their emission mechanism. However, there is a great difficulty in imaging Si nanocrystals in SiO2 and measuring their size distribution because of the lack of contrast in electron microscopy. We have used here a new method for imaging Si nanocrystals by using high resolution electron microscopy in conjunction with conventional electron microscopy in dark field conditions. Regarding the optical properties, the band-gap energies and photoluminescence have been measured by direct and independent methods. The results have allowed experimental determination, for the first time in this material, of the experimental Stokes shift between absorption and emission as a function of crystallite size. The experimental band-gap versus size correlates well with the most accurate theoretical predictions. Moreover, the photoluminescence energy emission versus crystallite size shows a parallel behaviour to that of band-gap energy. Consequently, the experimental Stokes shift is independent of nanocrystal size and is found to be 0.26±0.03 eV. This value is almost twice the energy of the Si-O vibration (0.134 eV). These results suggest that the dominant emission of Si nanocrystals passivated with SiO2 is a fundamental transition spatially located at the Si-SiO2 interface and with the assistance of a local Si-O vibration.

Tin Oxide One-Dimensional Nanomaterials Grown on Silver-Coated Substrates

2006 ◽  
Vol 15-17 ◽  
pp. 947-952
Author(s):  
Hyoun Woo Kim ◽  
Jong Woo Lee ◽  
S.H. Shim
Keyword(s):  
Electron Microscopy ◽  
Tin Oxide ◽  
Thermal Evaporation ◽  
Light Emission ◽  
High Resolution Electron Microscopy ◽  
X Ray Diffraction ◽  
Rutile Structure ◽  
One Dimensional ◽  
X Ray ◽  
Resolution Electron

We demonstrated the production of tin oxide (SnO2) one-dimensional (1D) nanostructures on silver (Ag)-coated substrates by the thermal evaporation of Sn powders. Scanning electron microscopy revealed that the product consisted of 1D nanomaterials with average diameters or widths in the range of 50-1300 nm. X-ray diffraction and high resolution electron microscopy coincidentally indicated that the nanostructures were mainly single-crystalline rutile structure of SnO2. The PL measurement with the Gaussian fitting showed visible light emission bands centered at 579 nm and 624 nm.

Recent Applications of High Resolution Electron Microscopy to Crystalline Arrays of Virus Particles

1978 ◽  
Vol 36 (3) ◽  
pp. 470-482 ◽  
Author(s):  
R.W. Horne
Keyword(s):  
Electron Microscopy ◽  
Image Processing ◽  
Analytical Techniques ◽  
Staining Technique ◽  
High Resolution Electron Microscopy ◽  
Optical Diffraction ◽  
Full Potential ◽  
Virus Particles ◽  
Resolution Electron ◽  
Wide Range

The technique of surrounding virus particles with a neutralised electron dense stain was described at the Fourth International Congress on Electron Microscopy, Berlin 1958 (see Home & Brenner, 1960, p. 625). For many years the negative staining technique in one form or another, has been applied to a wide range of biological materials. However, the full potential of the method has only recently been explored following the development and applications of optical diffraction and computer image analytical techniques to electron micrographs (cf. De Hosier & Klug, 1968; Markham 1968; Crowther et al., 1970; Home & Markham, 1973; Klug & Berger, 1974; Crowther & Klug, 1975). These image processing procedures have allowed a more precise and quantitative approach to be made concerning the interpretation, measurement and reconstruction of repeating features in certain biological systems.

One Million Direct Magnification Microscopy

1971 ◽  
Vol 29 ◽  
pp. 166-167
Author(s):  
J. A. Hugo ◽  
V. A. Phillips
Keyword(s):  
Electron Microscopy ◽  
High Resolution Electron Microscopy ◽  
Illumination Level ◽  
Level Of Detail ◽  
Photographic Emulsion ◽  
Low Contrast ◽  
Fluorescent Screen ◽  
Resolution Electron ◽  
Lattice Images ◽  
Electron Microscopes

A continuing problem in high resolution electron microscopy is that the level of detail visible to the microscopist while he is taking a picture is inferior to that obtainable by the microscope, readily readable on a photographic emulsion and visible in an enlargement made from the plate. Line resolutions, of 2Å or better are now achievable with top of the line 100kv microscopes. Taking the resolution of the human eye as 0.2mm, this indicates a need for a direct viewing magnification of at least one million. However, 0.2mm refers to optimum viewing conditions in daylight or the equivalent, and certainly does not apply to a (colored) image of low contrast and illumination level viewed on a fluorescent screen through a glass window by the dark-adapted eye. Experience indicates that an additional factor of 5 to 10 magnification is needed in order to view lattice images with line spacings of 2 to 4Å. Fortunately this is provided by the normal viewing telescope supplied with most electron microscopes.

Structural analysis of the surface-layer protein of spirillum serpens by high-resolution electron microscopy

1983 ◽  
Vol 41 ◽  
pp. 738-739
Author(s):  
W. H. Wu ◽  
R. M. Glaeser
Keyword(s):  
Electron Microscopy ◽  
Surface Layer ◽  
Structural Analysis ◽  
High Resolution ◽  
Low Dose ◽  
High Resolution Electron Microscopy ◽  
Optical Diffraction ◽  
Surface Layer Protein ◽  
Morphological Unit ◽  
Resolution Electron

Spirillum serpens possesses a surface layer protein which exhibits a regular hexagonal packing of the morphological subunits. A morphological model of the structure of the protein has been proposed at a resolution of about 25 Å, in which the morphological unit might be described as having the appearance of a flared-out, hollow cylinder with six ÅspokesÅ at the flared end. In order to understand the detailed association of the macromolecules, it is necessary to do a high resolution structural analysis. Large, single layered arrays of the surface layer protein have been obtained for this purpose by means of extensive heating in high CaCl2, a procedure derived from that of Buckmire and Murray. Low dose, low temperature electron microscopy has been applied to the large arrays.As a first step, the samples were negatively stained with neutralized phosphotungstic acid, and the specimens were imaged at 40,000 magnification by use of a high resolution cold stage on a JE0L 100B. Low dose images were recorded with exposures of 7-9 electrons/Å2. The micrographs obtained (Fig. 1) were examined by use of optical diffraction (Fig. 2) to tell what areas were especially well ordered.

Electron microscopy of rabbit FC crystals

1983 ◽  
Vol 41 ◽  
pp. 730-731
Author(s):  
Robert A. Grant ◽  
Laura L. Degn ◽  
Wah Chiu ◽  
John Robinson
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
High Resolution Electron Microscopy ◽  
Molecular Replacement ◽  
X Ray ◽  
X Ray Crystallography ◽  
Resolution Electron ◽  
Replacement Technique ◽  
Hydrated Crystal ◽  
Molecular Structure Analysis

Proteolytic digestion of the immunoglobulin IgG with papain cleaves the molecule into an antigen binding fragment, Fab, and a compliment binding fragment, Fc. Structures of intact immunoglobulin, Fab and Fc from various sources have been solved by X-ray crystallography. Rabbit Fc can be crystallized as thin platelets suitable for high resolution electron microscopy. The structure of rabbit Fc can be expected to be similar to the known structure of human Fc, making it an ideal specimen for comparing the X-ray and electron crystallographic techniques and for the application of the molecular replacement technique to electron crystallography. Thin protein crystals embedded in ice diffract to high resolution. A low resolution image of a frozen, hydrated crystal can be expected to have a better contrast than a glucose embedded crystal due to the larger density difference between protein and ice compared to protein and glucose. For these reasons we are using an ice embedding technique to prepare the rabbit Fc crystals for molecular structure analysis by electron microscopy.

Quality films from carbon fiber evaporation for thorough coverage of TEM grids

1988 ◽  
Vol 46 ◽  
pp. 418-419
Author(s):  
N. Tempel ◽  
M. C. Ledbetter
Keyword(s):  
Electron Microscopy ◽  
High Resolution Electron Microscopy ◽  
Carbon Films ◽  
Low Noise ◽  
Vacuum Evaporation ◽  
High Yield ◽  
Good Adhesion ◽  
Noise Structure ◽  
Resolution Electron ◽  
Carbon Foils

Carbon films have been a support of choice for high resolution electron microscopy since the introduction of vacuum evaporation of carbon. The desirable qualities of carbon films and methods of producing them has been extensively reviewed. It is difficult to get a high yield of grids by many of these methods, especially if virtually all of the windows must be covered with a tightly bonded, quality film of predictable thickness. We report here a method for producing carbon foils designed to maximize these attributes: 1) coverage of virtually all grid windows, 2) freedom from holes, wrinkles or folds, 3) good adhesion between film and grid, 4) uniformity of film and low noise structure, 5) predictability of film thickness, and 6) reproducibility.Our method utilizes vacuum evaporation of carbon from a fiber onto celloidin film and grid bars, adhesion of the film complex to the grid by carbon-carbon contact, and removal of the celloidin by acetone dissolution. Materials must be of high purity, and cleanliness must be rigorously maintained.

High resolution electron microscopy of lanthanum phosphate crystals

1978 ◽  
Vol 36 (1) ◽  
pp. 274-275
Author(s):  
J. C. Wheatley ◽  
J. M. Cowley
Keyword(s):  
Electron Microscopy ◽  
Catalytic Activity ◽  
High Resolution ◽  
Petroleum Industry ◽  
High Resolution Electron Microscopy ◽  
Lanthanum Phosphate ◽  
Good Catalyst ◽  
Resolution Electron ◽  
Good Catalytic Activity ◽  
Physical And Chemical

Rare-earth phosphates are of particular interest because of their catalytic properties associated with the hydrolysis of many aromatic chlorides in the petroleum industry. Lanthanum phosphates (LaPO4) which have been doped with small amounts of copper have shown increased catalytic activity (1). However the physical and chemical characteristics of the samples leading to good catalytic activity are not known.Many catalysts are amorphous and thus do not easily lend themselves to methods of investigation which would include electron microscopy. However, the LaPO4, crystals are quite suitable samples for high resolution techniques.The samples used were obtained from William L. Kehl of Gulf Research and Development Company. The electron microscopy was carried out on a JEOL JEM-100B which had been modified for high resolution microscopy (2). Standard high resolution techniques were employed. Three different sample types were observed: 669A-1-5-7 (poor catalyst), H-L-2 (good catalyst) and 27-011 (good catalyst).

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