A Model Based Iterative Reconstruction Algorithm For High Angle Annular Dark Field-Scanning Transmission Electron Microscope (HAADF-STEM) Tomography

2013 ◽  
Vol 22 (11) ◽  
pp. 4532-4544 ◽  
Author(s):  
S. V. Venkatakrishnan ◽  
L. F. Drummy ◽  
M. A. Jackson ◽  
M. De Graef ◽  
J. Simmons ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Reconstruction Algorithm ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
High Angle ◽  
Iterative Reconstruction Algorithm ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Stem Tomography

High-angle annular dark-field STEM imaging of doped semiconductor layers

1991 ◽  
Vol 49 ◽  
pp. 704-705
Author(s):  
D.D. Perovic ◽  
J.H. Paterson
Keyword(s):  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
High Angle ◽  
Axis Orientation ◽  
Undoped Material ◽  
Transmission Electron ◽  
Ultrathin Layers ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
P Type

With the development of crystal growth techniques such as molecular beam epitaxy (MBE), it is now possible to fabricate modulation-doped superlattices consisting of alternating ultrathin layers of n-and/or p-type material abruptly separated by undoped material. At sufficiently high dopant concentrations these abrupt layers may be imaged in cross section by electron microscopy. Pennycook et al. and Treacy et al. have used high angle annular dark-field (HAAD) imaging in the scanning transmission electron microscope (STEM) to image low levels of dopants (∼1 at. %) in semiconductors. This work is concerned with imaging boron and arsenic doped layers in silicon at levels « 1 at.%.Fig. 1 shows a HAAD image of a B-Si superlattice at the <110> zone-axis orientation taken at 100 kV using a VG HB501UX STEM. The bright vertical layers are the B-doped regions, containing ∼4 x 1020 B/cm3. The horizontal lines are due to beam instability while the image was recorded. Fig.2 shows a line scan across the same superlattice, recorded by scanning the beam across the specimen in a direction perpendicular to the layers.

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.

Theoretical considerations in lattice resolution high-angle annular dark-field imaging

1992 ◽  
Vol 50 (2) ◽  
pp. 1226-1227
Author(s):  
Adam Amali ◽  
Peter Rez
Keyword(s):  
Large Angle ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Theoretical Interpretation ◽  
High Angle ◽  
Dark Field Imaging ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Lattice Resolution

The highly coherent probe in the scanning transmission electron microscope(STEM) equipped with a with high angle annular dark field (HAADF) detector has become an important tool for high resolution work in the study of crystals.with potential for providing chemically sensitive information.The results of Pennycook and Boatner and the calculations of Kirkland et al clearly demonstrated that lattice resolution was possible using HAADF imaging.There has been other contributions since then.The theoretical interpretation of these images however remains controversial and other contributions have focussed on whether the imaging is coherent or incoherent.In the present work we analyse the various mechanisms that contribute to the large angle signal obtained in the HAADF detector.Bloch waves are used to describe the elastic dynamical scattering; and in the abscence of any strong Bragg reflections.the amplitude observed in the detector plane in the STEM may be represented by a simple convolution between the scattering function of the object and the probe.

Analytical High-Resolution TEM Study on Au/TiO2 Catalysts

1999 ◽  
Vol 589 ◽  
Author(s):  
T. Akita ◽  
K. Tanaka ◽  
S. Tsubota ◽  
M. Haruta
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Transmission Electron Microscope ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
High Resolution Tem ◽  
Electron Energy Loss

AbstractHRTEM(High-Resolution Transmission Electron Microscope), HAADF-STEM (High Angle Annular Dark Field Scanning Transmission Electron Microscope) and EELS(Electron Energy Loss Spectroscopy) techniques were applied for the characterization of Au/TiO2 catalysts. HAADFSTEM provides precise size distributions for Au particles smaller than ∼2nm in diameter. It was observed that many small particles under 2nm were supported on anatase TiO2 having a large surface area. The HAADF-STEM method was examined as a way to measure the shape of Au particles. EELS measurements were also used to examine the interface between Au and TiO2 support to study electronic structure effects.

ADF-STEM Imaging of Strained GaN0.045As0.955 Epitaxial Layers on (100) GaAs Substrates

2006 ◽  
Vol 982 ◽  
Author(s):  
X. Wu ◽  
M.D. Robertson ◽  
J.A. Gupta ◽  
J.-M. Baribeau ◽  
J.C. Bennett ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Gaas Substrate ◽  
Misfit Strain ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Gaas Substrates ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field

ABSTRACTThe annular dark field (ADF) image contrast of a 0.92% tensile strained GaN0.045As0.955 layer on GaAs substrate was studied with a scanning transmission electron microscope (STEM) as a function of ADF detector inner semi-angles ranging from 28 mrad to 90 mrad. The GaN0.045As0.955 layers were brighter than the surrounding GaAs for the values of ADF detector semiangle up to 65 mrad, and the measured contrast decreased with increasing ADF detector inner semi-angle. For a 37 nm thick specimen, the GaN0.045As0.955 intensity is about 13% higher than that of GaAs in the 28 mrad ADF detector inner semi-angle. Multislice simulations show that the displacement around substitutional N atoms plays an important role in the observed ADF-STEM contrast, while the contribution to the contrast due to misfit strain between GaN0.045As0.955 and GaAs is small.

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.

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