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.

RDF Analysis of Ion-Amorphized SiO2 and SiC from Electron Diffraction using Post-Specimen Scanning in the Field-Emission Scanning Transmission Electron Microscope

1997 ◽  
Vol 504 ◽  
Author(s):  
David C. Bell ◽  
Anthony J. Garratt-Reed ◽  
Linn W. Hobbst
Keyword(s):  
Electron Microscope ◽  
Electron Diffraction ◽  
Field Emission ◽  
Transmission Electron Microscope ◽  
Spherical Aberration ◽  
Scanning Transmission Electron Microscope ◽  
Objective Lens ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission

ABSTRACTRadial density functions (RDFs) provide important information about short- and ntermediaterange structure of topologically-disordered materials such as glasses and irradiation-amorphized materials. We have determined RDFs for irradiation-amorphized SiO2, AIPO4 and SiC by energy-filtered electron diffraction methods in a field-emission scanning transmission electron microscope (FEG-STEM) equipped with a digital parallel-detection electron energy-loss spectrometer. Post-specimen rocking was used to minimize the effects of spherical aberration in the objective lens, which interfere with the acquisition of data collected by pre-specimen rocking. Useful energy-filtered data has been collected beyond an angular range defined by q = 2 sin(Θ/2)/λ = 25 nm−1

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.

Unique Features of a High Resolution Scanning Transmission Electron Microscope

1974 ◽  
Vol 32 ◽  
pp. 404-405
Author(s):  
J. W. Wiggins ◽  
M. Beer ◽  
D. C. Woodruff ◽  
J. A. Zubin
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Transmission Electron Microscope ◽  
Heavy Atom ◽  
Scanning Transmission Electron Microscope ◽  
Objective Lens ◽  
Optical Parameters ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission

A high resolution scanning transmission electron microscope has been constructed and is operating. The initial task of this instrument is to attempt the sequencing of DNA by heavy-atom specific staining. It is also suitable for many other biological investigations requiring high resolution, low contamination and minimum radiation damage.The basic optical parameters are: 20 to 100 KV acceleration potential, objective lens focal length of 1.0 mm. with Cs = 0.7 mm., and two additional lenses designated as condensor and diffraction lenses. The purpose of the condensor lens is to provide a parallel beam incident to the objective, and the diffraction lens produces an image of the back focal plane of the objective in the plane of an annular detector.

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.

Development of a Real-Time Elemental Mapping System in a Scanning Transmission Electron Microscope

2000 ◽  
Vol 6 (S2) ◽  
pp. 178-179
Author(s):  
K. Kaji Ueda ◽  
T. Aoyama ◽  
S. Taya ◽  
H. Tanaka ◽  
S. Isakozawa
Keyword(s):  
Electron Microscope ◽  
Real Time ◽  
Transmission Electron Microscope ◽  
Scanning Transmission Electron Microscope ◽  
Objective Lens ◽  
Elemental Mapping ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Mapping System ◽  
Scanning Transmission

The ability to obtain elemental maps in a transmission electron microscope (TEM) or scanning transmission electron microscope (STEM) is extremely useful in the analysis of materials, and semiconductor devices such as ULSI's and GMR heads. Hitachi has developed a new type of elemental mapping system, consisting of a STEM (Hitachi, HD-2000) equipped with a two-window electron energy filter. In-situ calculation of the energy-filtered signal makes it possible to observe real time elemental mapping images with nanometer resolution.Figure 1 shows a schematic of the elemental mapping system. In the STEM, electrons are generated from a cold field emission gun and accelerated to a potential of 200 kV. The electrons arc focused by the objective lens into a small probe (<1 nm), which is then rastered over the specimen using scanning coils. Transmitted electrons are collected by an energy filter, which is located beneath the specimen., and consists of quadrupole lenses, a magnetic prism spectrometer and two kinds of electron beam energy detectors.

scholarly journals Determination of Dy substitution site in Nd2−xDyxFe14B by HAADF-STEM and illustration of magnetic anisotropy of “g” and “f” sites, before and after substitution

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Syed Kamran Haider ◽  
Min-Chul Kang ◽  
Jisang Hong ◽  
Young Soo Kang ◽  
Cheol-Woong Yang ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Magnetic Anisotropy ◽  
Transmission Electron Microscope ◽  
Magnetic Moment ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Product Analysis ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission

AbstractNd2Fe14B and Nd2−xDyxFe14B (x = 0.25, 0.50) particles were prepared by the modified co-precipitation followed by reduction–diffusion process. Bright field scanning transmission electron microscope (BF-STEM) image revealed the formation of Nd–Fe–B trigonal prisms in [− 101] viewing zone axis, confirming the formation of Nd2Fe14B/Nd2−xDyxFe14B. Accurate site for the Dy substitution in Nd2Fe14B crystal structure was determined as “f” site by using high-angle annular dark field scanning transmission electron microscope (HAADF-STEM). It was found that all the “g” sites are occupied by the Nd, meanwhile Dy occupied only the “f” site. Anti-ferromagnetic coupling at “f” site decreased the magnetic moment values for Nd1.75Dy0.25Fe14B (23.48 μB) and Nd1.5Dy0.5Fe14B (21.03 μB) as compared to Nd2Fe14B (25.50 μB). Reduction of magnetic moment increased the squareness ratio, coercivity and energy product. Analysis of magnetic anisotropy at constant magnetic field confirmed that “f” site substitution did not change the patterns of the anisotropy. Furthermore, magnetic moment of Nd2Fe14B, Nd2−xDyxFe14B, Nd (“f” site), Nd (“g” site) and Dy (“f” site) was recorded for all angles between 0° and 180°.

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