the resolution

[张辉]

Greetings,

I am a little bit confused about the resolution in the probe array section. Is it the step size to discretize the potential? why does it determine the scattering angle? and are there any principles to chose the value? Thank you very much.

Regards,

Hui

[Christoph Koch]

Hello,

 

The resolution of the probe array is indeed the pixel size (or step size) with which the wave function of the incident and propagating electron probe is being sampled. It determines the scattering angle, since the largest scattering angle that can be sampled by the probe array is inverse proportional to the pixel size. The smaller the pixel size, the finer the details you can sample, the larger the scattering angles that your diffraction patterns will contain.

In order to avoid aliasing artefacts, the scattering angle is limited to 2/3 of the Nyquist frequency times wavelength of the electron beam. This means that the maximum scattering angle theta_max is computed according to:

theta_max = 2/3*0.5*lambda/pixelSize = lambda/(3*pixelSize).

 

With best regards,

Christoph.

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[张辉]

Greetings Chris,

Thank you so much for your detailed explanations.

Regards,

Hui