Transmission Electron Microscopy of Shape-Controlled Nanocrystals and Their Assemblies 指導教授 : 王聖璋 教授 學生 : 張詠新 學號 : MA10106 電子顯微鏡學 -Paper Survey J. Phys. Chem. B 2000, 104, Z. L. Wang

2.3. The White and Dark Spots in the Image, Which Represent Atoms? If the specimen is so thin that the projected potential satisfies |σVp| << 1 -To answer this question, one must examine the imaging conditions 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 t obj 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 Schr Ö dinger equation under given boundary conditions

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 The White and Dark Spots in the Image, Which Represent Atoms?

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