J. Phys. Chem. B 2000, 104, 1153 - 1175
Transmission Electron Microscopy
of Shape-Controlled Nanocrystals
and Their Assemblies
Z. L. Wang
電子顯微鏡學-Paper Survey
指導教授: 王聖璋 教授
學生: 張詠新
學號: MA10106
2.3. The White and Dark Spots in the
Image, Which Represent Atoms?
-To answer this question, one must examine the imaging conditions
If the specimen is so thin that the projected potential
satisfies |σVp| << 1
The second term is the interference result of the central
transmitted beam with the Bragg reflected beams.
2.3. The White and Dark Spots in the
Image, Which Represent Atoms?
The optimum shape of the lens transfer function tobj is a
narrow Gaussian-like function with a small tail
On the other hand, the form of the ts(x,y, △f) function
depends on the defocus of the objective lens; contrast reversal
is possible simply by changing the defocus of the objective lens.
The dynamic diffraction process is to solve the SchrÖdinger
equation under given boundary conditions
2.3. The White and Dark Spots in the
Image, Which Represent Atoms?
Theoretically simulated images for a decahedral Au particle at various orientations and
at focuses of (A) △f 42 nm and (B)△f 70 nm, illustrating the contrast reversal in the two
cases.
Thanks for your attention!
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