Some Quantification Problems in Parallel EELS Images

1990 ◽  
Vol 48 (2) ◽  
pp. 36-37
Author(s):  
G. Botton ◽  
G. L’Espérance ◽  
M.D. Ball ◽  
C.E. Gallerneault
Keyword(s):  
Electron Microscope ◽  
Imaging System ◽  
Signal To Noise Ratio ◽  
Scanning Transmission Electron Microscope ◽  
Acquisition Time ◽  
Thickness Variation ◽  
Transmission Electron ◽  
Distribution Of Elements ◽  
Scanning Transmission ◽  
Present Distribution

The recently developed parallel electron energy loss spectrometers (PEELS) have led to a significant reduction in spectrum acquisition time making EELS more useful in many applications in material science. Dwell times as short as 50 msec per spectrum with a PEELS coupled to a scanning transmission electron microscope (STEM), can make quantitative EEL images accessible. These images would present distribution of elements with the high spatial resolution inherent to EELS. The aim of this paper is to briefly investigate the effect of acquisition time per pixel on the signal to noise ratio (SNR), the effect of thickness variation and crystallography and finally the energy stability of spectra when acquired in the scanning mode during long periods of time.The configuration of the imaging system is the following: a Gatan PEELS is coupled to a CM30 (TEM/STEM) electron microscope, the control of the spectrometer and microscope is performed through a LINK AN10-85S MCA which is interfaced to a IBM RT 125 (running under AIX) via a DR11W line.

Resolution in the Scanning Transmission Electron Microscope

1972 ◽  
Vol 30 ◽  
pp. 454-455
Author(s):  
M. G. R. Thomson
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Spherical Aberration ◽  
Signal To Noise Ratio ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Objective Lens ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission

The variation of contrast and signal to noise ratio with change in detector solid angle in the high resolution scanning transmission electron microscope was discussed in an earlier paper. In that paper the conclusions were that the most favourable conditions for the imaging of isolated single heavy atoms were, using the notation in figure 1, either bright field phase contrast with β0⋍0.5 α0, or dark field with an annular detector subtending an angle between ao and effectively π/2.The microscope is represented simply by the model illustrated in figure 1, and the objective lens is characterised by its coefficient of spherical aberration Cs. All the results for the Scanning Transmission Electron Microscope (STEM) may with care be applied to the Conventional Electron Microscope (CEM). The object atom is represented as detailed in reference 2, except that ϕ(θ) is taken to be the constant ϕ(0) to simplify the integration. This is reasonable for θ ≤ 0.1 θ0, where 60 is the screening angle.

Identifying and Correcting Scan Noise and Drift in the Scanning Transmission Electron Microscope

2013 ◽  
Vol 19 (4) ◽  
pp. 1050-1060 ◽  
Author(s):  
Lewys Jones ◽  
Peter D. Nellist
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Electromagnetic Interference ◽  
Signal To Noise Ratio ◽  
Scanning Transmission Electron Microscope ◽  
Great Sensitivity ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Recorded Data

AbstractThe aberration-corrected scanning transmission electron microscope has great sensitivity to environmental or instrumental disturbances such as acoustic, mechanical, or electromagnetic interference. This interference can introduce distortions to the images recorded and degrade both signal noise and resolution performance. In addition, sample or stage drift can cause the images to appear warped and leads to unreliable lattice parameters being exhibited. Here a detailed study of the sources, natures, and effects of imaging distortions is presented, and from this analysis a piece of image reconstruction code has been developed that can restore the majority of the effects of these detrimental image distortions for atomic-resolution data. Example data are presented, and the performance of the restored images is compared quantitatively against the as-recorded data. An improvement in apparent resolution of 16% and an improvement in signal-to-noise ratio of 30% were achieved, as well as correction of the drift up to the precision to which it can be measured.

Multislice Simulation of Adf Stem Images

1987 ◽  
Vol 45 ◽  
pp. 188-191
Author(s):  
E. J. Kirkland ◽  
R. F. Loane ◽  
J. Silcox
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Scattering Amplitude ◽  
Signal To Noise Ratio ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Heavy Atoms ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field

The multislice method (e.g. Goodman and Moodie) of simulating bright field conventional transmission electron microscope (BF-CTEM) images of crystalline specimens can be extended to simulation of scanning transmission electron microscope (STEM) images of similar specimens in the annular dark field (ADF) mode. According to the reciprocity theorem (Pogany and Turner and Cowley) BF-CTEM would be equivalent to BF STEM with a point detector. Such a detector (STEM) however would yield an exceedingly small signal to noise ratio. Thus, STEM has found more use in the ADF mode (e.g. Crewe et al.) exploiting the large contrast arising from heavy atoms. In BF imaging (CTEM and STEM) the constrast is roughly proportional to the scattering amplitude f α Z3/4 whereas in DF (CTEM and STEM) imaging it is roughly proportional to the scattering cross σ α Z3/2 where Z is atomic number, a form that is advantageous foatom discrimination.

The High Resolution Scanning Transmission Electron Microscope

1974 ◽  
Vol 32 ◽  
pp. 316-317
Author(s):  
A. V. Crewe
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
High Vacuum ◽  
Scanning Transmission Electron Microscope ◽  
Ultra High Vacuum ◽  
Resolving Power ◽  
Imaging Characteristics ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
The Moment

The high resolution STEM is now a fact of life. I think that we have, in the last few years, demonstrated that this instrument is capable of the same resolving power as a CEM but is sufficiently different in its imaging characteristics to offer some real advantages.It seems possible to prove in a quite general way that only a field emission source can give adequate intensity for the highest resolution^ and at the moment this means operating at ultra high vacuum levels. Our experience, however, is that neither the source nor the vacuum are difficult to manage and indeed are simpler than many other systems and substantially trouble-free.

Development of 200 kV Scanning-Transmission Electron Microscope

1974 ◽  
Vol 32 ◽  
pp. 410-411
Author(s):  
H. Koike ◽  
S. Sakurai ◽  
K. Ueno ◽  
M. Watanabe
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Scanning Transmission Electron Microscope ◽  
The Other ◽  
Morphological Observation ◽  
Magnetic Domains ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Backscattered Electron ◽  
Increasing Demand

In recent years, there has been increasing demand for higher voltage SEMs, in the field of surface observation, especially that of magnetic domains, dislocations, and electron channeling patterns by backscattered electron microscopy. On the other hand, the resolution of the CTEM has now reached 1 ∼ 2Å, and several reports have recently been made on the observation of atom images, indicating that the ultimate goal of morphological observation has beem nearly achieved.

To What Extent are Inelastically Scattered Electrons Useful in the Stem?

1973 ◽  
Vol 31 ◽  
pp. 286-287 ◽  
Author(s):  
H. Rose
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Electron Correlation ◽  
Quantum Noise ◽  
Collection Efficiency ◽  
Scanning Transmission Electron Microscope ◽  
Electron Cloud ◽  
Scanning Time ◽  
Transmission Electron ◽  
Scanning Transmission

The scanning transmission electron microscope offers the possibility of utilizing inelastically scattered electrons. Use of these electrons in addition to the elastically scattered electrons should reduce the scanning time (dose) Which is necessary to keep the quantum noise below a certain level. Hence it should lower the radiation damage. For high resolution, Where the collection efficiency of elastically scattered electrons is small, the use of Inelastically scattered electrons should become more and more favorable because they can all be detected by means of a spectrometer. Unfortunately, the Inelastic scattering Is a non-localized interaction due to the electron-electron correlation, occurring predominantly at the circumference of the atomic electron cloud.

A General Method for Spectrometer Design in the Scoff Approximation

1976 ◽  
Vol 34 ◽  
pp. 538-539
Author(s):  
J. R. Fields
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Energy Analysis ◽  
Incident Beam ◽  
Scanning Transmission Electron Microscope ◽  
Chemical Identification ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
General Method

The energy analysis of electrons scattered by a specimen in a scanning transmission electron microscope can improve contrast as well as aid in chemical identification. In so far as energy analysis is useful, one would like to be able to design a spectrometer which is tailored to his particular needs. In our own case, we require a spectrometer which will accept a parallel incident beam and which will focus the electrons in both the median and perpendicular planes. In addition, since we intend to follow the spectrometer by a detector array rather than a single energy selecting slit, we need as great a dispersion as possible. Therefore, we would like to follow our spectrometer by a magnifying lens. Consequently, the line along which electrons of varying energy are dispersed must be normal to the direction of the central ray at the spectrometer exit.

Background subtraction in STEM energy-loss mapping

1984 ◽  
Vol 42 ◽  
pp. 568-569
Author(s):  
R.D. Leapman ◽  
K.E. Gorlen ◽  
C.R. Swyt
Keyword(s):  
Energy Loss ◽  
Signal To Noise Ratio ◽  
Statistical Error ◽  
Scanning Transmission Electron Microscope ◽  
Reference Image ◽  
Inverse Power Law ◽  
Transmission Electron ◽  
Least Squares Fit ◽  
Scanning Transmission ◽  
Single Number

The determination of elemental distributions by electron energy loss spectroscopy necessitates removal of the non-characteristic spectral background from a core-edge at each point in the image. In the scanning transmission electron microscope this is made possible by computer controlled data acquisition. Data may be processed by fitting the pre-edge counts, at two or more channels, to an inverse power law, AE-r, where A and r are parameters and E is energy loss. Processing may be performed in real-time so a single number is saved at each pixel. Detailed analysis, shows that the largest contribution to noise comes from statistical error in the least squares fit to the background. If the background shape remains constant over the entire image, the signal-to-noise ratio can be improved by fitting only one parameter. Such an assumption is generally implicit in subtraction of the “reference image” in energy selected micrographs recorded in the CTEM with a Castaing-Henry spectrometer.

Secondary electron imaging of YBa2Cu3O7-x high-Tc superconductors in Scanning Transmission Electron Microscope

1989 ◽  
Vol 47 ◽  
pp. 684-685
Author(s):  
D. R. Liu ◽  
D. B. Williams
Keyword(s):  
Electron Microscope ◽  
Secondary Electron ◽  
Scanning Transmission Electron Microscope ◽  
Superconducting Phase ◽  
Contrast Imaging ◽  
High Tc ◽  
Bright Contrast ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Electron Imaging

The secondary electron imaging technique in a scanning electron microscope (SEM) has been used first by Millman et al. in 1987 to distinguish between the superconducting phase and the non-superconducting phase of the YBa2Cu3O7-x superconductors. They observed that, if the sample was cooled down below the transition temperature Tc and imaged with secondary electrons, some regions in the image would show dark contrast whereas others show bright contrast. In general, the contrast variation of a SEM image is the variation of the secondary electron yield over a specimen, which in turn results from the change of topography and conductivity over the specimen. Nevertheless, Millman et al. were able to demonstrate with their experimental results that the dominant contrast mechanism should be the conductivity variation and that the regions of dark contrast were the superconducting phase whereas the regions of bright contrast were the non-superconducting phase, because the latter was a poor conductor and consequently, the charge building-up resulted in high secondary electron emission. This observation has since aroused much interest amoung the people in electron microscopy and high Tc superconductivity. The present paper is the preliminary report of our attempt to carry out the secondary electron imaging of this material in a scanning transmission electron microscope (STEM) rather than in a SEM. The advantage of performing secondary electron imaging in a TEM is obvious that, in a TEM, the spatial resolution is higher and many more complementary techniques, e.g, diffraction contrast imaging, phase contrast imaging, electron diffraction and various microanalysis techniques, are available.

Sign in / Sign up

Export Citation Format

Share Document