scholarly journals Modern Microscopy on the Light Side: TEM in the Trenches

1993 ◽  
Vol 1 (4) ◽  
pp. 6-10
Author(s):  
Stephen E. Rice
Keyword(s):  
Science Fiction ◽  
Great Promise ◽  
Electron Holography ◽  
Imaging Device ◽  
X Ray ◽  
Transmission Electron ◽  
Electron Microscopes ◽  
Light Side ◽  
Convergent Beam ◽  
Made In

Great strides have been made in the last decade in high resolution transmission electron microscopes (TEMs) which can also provide elemental information via energy dispersive X-ray analysis (EDX) or energy loss spectroscopy (EELS), and proponents of various TEM techniques make bold claims. Convergent beam elecjron diffraction and microdifff action shine as techniques for defect structure analysis and means for solving crystal structures. The spectroscopies can now be used to map chemical state information at a level which until recently might be encountered in science fiction. As a pure imaging device, electron holography holds great promise for providing Ehe ultimate (would you believe 0.1Å?) imaging resolution. Although conventional TEMs will never approach this, it appears that we are learning more and more about less and less, until we will soon know everything there is to know about nothing.

The relevance of local lattice parameter measurements using CBED

1988 ◽  
Vol 46 ◽  
pp. 1006-1007
Author(s):  
Hamish L. Fraser
Keyword(s):  
Materials Science ◽  
Lattice Parameter ◽  
Physical Situation ◽  
Thin Foils ◽  
Transmission Electron ◽  
Local Lattice ◽  
The Subject ◽  
Electron Microscopes ◽  
Convergent Beam ◽  
Made In

Since the development of transmission electron microscopes in which the electron beam may be caused to be incident on the sample in the form of a convergent probe, much work has been aimed at the use of convergent beam electron diffraction (CBED) in materials science. One of the techniques afforded by CBED permits the measurement of lattice parameters on a scale more or less defined by the diameter of the probe at the sample, and so a powerful means of determining local distortions has become available. While this technique appears to be very exciting, as is shown below, the necessary use of thin foils results in the possibility of surface relaxations modifying the stress fields of a given distortion, and this raises the question of the relevance of measurements made in thin foils to the physical situation in the bulk. This question is the subject of this paper.

Removing Substrate Background in TEM Microanalysis

1974 ◽  
Vol 32 ◽  
pp. 568-569
Author(s):  
John C. Russ ◽  
Nicholas C. Barbi
Keyword(s):  
Electrical Conductivity ◽  
Rapid Growth ◽  
Organic Film ◽  
Absolute Concentration ◽  
Background Signal ◽  
X Ray ◽  
Elemental Concentrations ◽  
Transmission Electron ◽  
Electron Microscopes ◽  
The Continuum

The rapid growth of interest in attaching energy-dispersive x-ray analysis systems to transmission electron microscopes has centered largely on microanalysis of biological specimens. These are frequently either embedded in plastic or supported by an organic film, which is of great importance as regards stability under the beam since it provides thermal and electrical conductivity from the specimen to the grid.Unfortunately, the supporting medium also produces continuum x-radiation or Bremsstrahlung, which is added to the x-ray spectrum from the sample. It is not difficult to separate the characteristic peaks from the elements in the specimen from the total continuum background, but sometimes it is also necessary to separate the continuum due to the sample from that due to the support. For instance, it is possible to compute relative elemental concentrations in the sample, without standards, based on the relative net characteristic elemental intensities without regard to background; but to calculate absolute concentration, it is necessary to use the background signal itself as a measure of the total excited specimen mass.

Transmission electron microscope studies in special ceramics

1978 ◽  
Vol 36 (1) ◽  
pp. 268-269
Author(s):  
A. Zangvil ◽  
L.J. Gauckler ◽  
G. Schneider ◽  
M. Rühle
Keyword(s):  
Phase Diagrams ◽  
Crystal Structures ◽  
Thin Foil ◽  
Limited Extent ◽  
Complex Materials ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Electron Microscopes ◽  
Lattice Resolution

The use of high temperature special ceramics which are usually complex materials based on oxides, nitrides, carbides and borides of silicon and aluminum, is critically dependent on their thermomechanical and other physical properties. The investigations of the phase diagrams, crystal structures and microstructural features are essential for better understanding of the macro-properties. Phase diagrams and crystal structures have been studied mainly by X-ray diffraction (XRD). Transmission electron microscopy (TEM) has contributed to this field to a very limited extent; it has been used more extensively in the study of microstructure, phase transformations and lattice defects. Often only TEM can give solutions to numerous problems in the above fields, since the various phases exist in extremely fine grains and subgrain structures; single crystals of appreciable size are often not available. Examples with some of our experimental results from two multicomponent systems are presented here. The standard ion thinning technique was used for the preparation of thin foil samples, which were then investigated with JEOL 200A and Siemens ELMISKOP 102 (for the lattice resolution work) electron microscopes.

Reduction of Specimen Contamination in Electron-Beam Instruments

1976 ◽  
Vol 34 ◽  
pp. 576-577
Author(s):  
G. Lehmpfuhl ◽  
P. J. Smith
Keyword(s):  
Electron Beam ◽  
Cold Trap ◽  
Beam Diameter ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Hydrocarbon Molecules ◽  
Electron Microscopes ◽  
Combination Of Methods ◽  
Convergent Beam ◽  
Very High

Specimens being observed with electron-beam instruments are subject to contamination, which is due to polymerization of hydrocarbon molecules by the beam. This effect becomes more important as the size of the beam is reduced. In convergent-beam studies with a beam diameter of 100 Å, contamination was observed to grow on samples at very high rates. Within a few seconds needles began forming under the beam on both the top and the underside of the sample, at growth rates of 400-500 Å/s, severely limiting the time available for observation. Such contamination could cause serious difficulty in examining a sample with the new scanning transmission electron microscopes, in which the beam is focused to a few angstroms.We have been able to reduce the rate of contamination buildup by a combination of methods: placing an anticontamination cold trap in the sample region, preheating the sample before observation, and irradiating the sample with a large beam before observing it with a small beam.

Convergent-beam electron diffraction at high spatial resolution

1992 ◽  
Vol 50 (2) ◽  
pp. 1152-1153 ◽  
Author(s):  
J W Steeds
Keyword(s):  
Electron Diffraction ◽  
High Temperature Superconductors ◽  
Bloch Wave ◽  
Convergent Beam Electron Diffraction ◽  
Beam Electron ◽  
Energy Filtering ◽  
Small Probe ◽  
Transmission Electron ◽  
Electron Microscopes ◽  
Convergent Beam

That the techniques of convergent beam electron diffraction (CBED) are now widely practised is evident, both from the way in which they feature in the sale of new transmission electron microscopes (TEMs) and from the frequency with which the results appear in the literature: new phases of high temperature superconductors is a case in point. The arrival of a new generation of TEMs operating with coherent sources at 200-300kV opens up a number of new possibilities.First, there is the possibility of quantitative work of very high accuracy. The small probe will essentially eliminate thickness or orientation averaging and this, together with efficient energy filtering by a doubly-dispersive electron energy loss spectrometer, will yield results of unsurpassed quality. The Bloch wave formulation of electron diffraction has proved itself an effective and efficient method of interpreting the data. The treatment of absorption in these calculations has recently been improved with the result that <100> HOLZ polarity determinations can now be performed on III-V and II-VI semiconductors.

Current Status of Solid-State X-Ray Systems

1985 ◽  
Vol 43 ◽  
pp. 158-161
Author(s):  
Martin Peckerar ◽  
Anastasios Tousimis
Keyword(s):  
Solid State ◽  
Electric Fields ◽  
Spectral Lines ◽  
Current Status ◽  
Mobile Charge ◽  
Electron Hole ◽  
X Ray ◽  
Sensing Systems ◽  
Transmission Electron ◽  
Electron Microscopes

Solid state x-ray sensing systems have been used for many years in conjunction with scanning and transmission electron microscopes. Such systems conveniently provide users with elemental area maps and quantitative chemical analyses of samples. Improvements on these tools are currently sought in the following areas: sensitivity at longer and shorter x-ray wavelengths and minimization of noise-broadening of spectral lines. In this paper, we review basic limitations and recent advances in each of these areas. Throughout the review, we emphasize the systems nature of the problem. That is. limitations exist not only in the sensor elements but also in the preamplifier/amplifier chain and in the interfaces between these components.Solid state x-ray sensors usually function by way of incident photons creating electron-hole pairs in semiconductor material. This radiation-produced mobile charge is swept into external circuitry by electric fields in the semiconductor bulk.

X-ray mapping without STEM

1994 ◽  
Vol 52 ◽  
pp. 508-509
Author(s):  
Judith M. Brock ◽  
Max T. Otten
Keyword(s):  
Life Science ◽  
Materials Science ◽  
Chemical Elements ◽  
Full Description ◽  
Scanning System ◽  
Elemental Distribution ◽  
X Ray ◽  
Transmission Electron ◽  
Distribution Of Elements ◽  
Made In

A knowledge of the distribution of chemical elements in a specimen is often highly useful. In materials science specimens features such as grain boundaries and precipitates generally force a certain order on mental distribution, so that a single profile away from the boundary or precipitate gives a full description of all relevant data. No such simplicity can be assumed in life science specimens, where elements can occur various combinations and in different concentrations in tissue. In the latter case a two-dimensional elemental-distribution image is required to describe the material adequately. X-ray mapping provides such of the distribution of elements.The big disadvantage of x-ray mapping hitherto has been one requirement: the transmission electron microscope must have the scanning function. In cases where the STEM functionality – to record scanning images using a variety of STEM detectors – is not used, but only x-ray mapping is intended, a significant investment must still be made in the scanning system: electronics that drive the beam, detectors for generating the scanning images, and monitors for displaying and recording the images.

In-Situ Growth and Polygonization of Epitaxial Passive Oxide Films on Nanoparticles of Iron

2001 ◽  
Vol 7 (S2) ◽  
pp. 1234-1235
Author(s):  
K.K. Fung ◽  
X.X. Zhang ◽  
Y.S. Kwok ◽  
Boxiong Qin
Keyword(s):  
Shell Morphology ◽  
Iron Core ◽  
X Ray Diffraction ◽  
X Ray ◽  
Gas Condensation ◽  
Transmission Electron ◽  
Image Position ◽  
Convergent Beam ◽  
Oxidation And Corrosion

Over the years, the study of the oxidation of nanoparticles of iron by transmission electron microscopy (TEM), Mossbauer spectroscopy and X-ray diffraction has established that nanoparticles of iron have a core-shell morphology in which the iron core is enclosed by shell of polycrystalline shell of ultrasmall γ-Fe2O3 and Fe3O4 crystallites. Recently, passivated nanoparticles of iron prepared by gas condensation of plasma evaporated vapor in Tianjin University exhibit remarkable resistance to further oxidation and corrosion in air and water. We have showed by TEM that these nanoparticles of iron are protected by a 4 nm epitaxial shell of γ-Fe2O3. The epitaxial orientation relationship, established by convergent beam electron diffraction from a nanoparticle, is as follows:The [001] diffraction pattern of the oxide is rotated by 45° about a cubic axis relative to that of iron.

Aberration-corrected HRTEM of the Incommensurate Misfit Layer Compound (PbS)1.14NbS2

2007 ◽  
Vol 1026 ◽  
Author(s):  
Magnus Garbrecht ◽  
Erdmann Spiecker ◽  
Wolfgang Jäger ◽  
Karsten Tillmann
Keyword(s):  
Spherical Aberration ◽  
Atomic Scale ◽  
Transition Metal Dichalcogenide ◽  
Layer Compound ◽  
X Ray ◽  
Medium Voltage ◽  
Transmission Electron ◽  
Interesting Class ◽  
Electron Microscopes ◽  
Set Up

AbstractThe development of tunable spherical aberration (Cs) imaging correctors for medium-voltage transmission electron microscopes (TEM) offers new opportunities for atomic-scale in-vestigations of materials. A very interesting class of microstructures regarding a variety of dif-ferent physical properties are the transition metal dichalcogenide misfit layer compounds exhibit-ing a high density of incommensurate interfaces due to their stacked nature. In the present study, the benefits coming along with the set-up of negative CS imaging (NCSI) conditions (in TEM) are demonstrated by means of different examples regarding local inhomogeneities in (PbS)1.14NbS2 crystals that can not be dissected in such detail by averaging x-ray techniques.

scholarly journals Surface Modified Ni Nanoparticles Produced by the Electrical Explosion of Wire

2015 ◽  
Vol 233-234 ◽  
pp. 513-516 ◽  
Author(s):  
A.P. Safronov ◽  
Galina V. Kurlyandskaya ◽  
S.M. Bhagat ◽  
I.V. Beketov ◽  
A.M. Murzakaev ◽  
...  
Keyword(s):  
Room Temperature ◽  
Electrical Explosion ◽  
Resonant Absorption ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cell Parameters ◽  
Transmission Electron ◽  
Average Size ◽  
Surface Modified ◽  
Made In

Spherical nickel nanoparticles were prepared by the electrical explosion of wire. The as-prepared nanoparticles were modified immediately after fabrication at room temperature in order to provide tunable surface properties with focus on the development of composites filled with nanoparticles. Following liquid modificators were used: hexane, toluene and the solution of polystyrene in toluene. In one case the surface modification by carbon was made in gas phase as a result of hydrocarbon injection. The average size of the nanoparticles was about 50 nm and unit cell parameters were close to 0.351 nm. Detailed characterization was done by X-ray diffraction, transmission electron microscopy, and magnetization measurements. Sphericity was also checked using microwave resonant absorption.

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