Simulation of HAADF-STEM Images

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Simulation of HAADF-STEM Images

Many theoretical models for HAADF-STEM images were initially developed for crystalline materials. The space travelled by the fast electron beam in STEM can be divided into three processes: from the source to the specimen; inside the specimen; and from the specimen to the detector. In the modeling, only the overall effects on the wave functions entering and exiting the specimen are taken into account.

In STEM analysis, the effect of the beam–specimen interaction in modifying the probe wave function into the sample exit wave function can be modeled using either the Bloch wave approach [1,2] or a multislice approach. [3,4]

Table 2581. Techniques of simulation of ADF-STEM images.

Techniques	Characteristics	Reference
TDS (thermal diffuse scattering) scattering	Thermal vibrations in a crystalline solid scatter intensities out of the Bragg diffracted beams to form a diffuse background in the diffraction pattern.	[5,6]
Debye–Waller factor	An extra Debye–Waller factor can be added to the cross section of TDS (thermal diffuse scattering) scattering to simulate the effect of a random strain field.	[5,6]
Multislice	Divides the sample into a sequence of thin layers and then propagates the electron beam perpendicular to each layer. The variation of image and diffraction intensities with sample thickness can be simulated

[1] Nellist P, Pennycook SJ. Ultramicroscopy 1999;78:111–24.
[2] Peng Y, Nellist PD, Pennycook SJ. J Electron Microsc 2004;53:257–66.
[3] Kirkland EJ, Loane RF, Silcox J. Ultramicroscopy 1987;23:77–96.
[4] Cowley JM, Moodie AF. Acta Crystallogr 1957;10:609–19.
[5] C. R. Hall and P. B. Hirsch, Proc. R. Soc. London, Ser. A 286, 158 (1965).
[6] John M. Cowley, Diffraction Physics, 3rd revised ed. (North Holland, Amsterdam, 1995), p. 157.

Practical Electron Microscopy and Database

An Online Book, Second Edition by Dr. Yougui Liao (2006)

Simulation of HAADF-STEM Images