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Published on: March 5, 2014
Caustic imaging of gallium droplets using mirror electron microscopy
S M Kennedy1, C X Zheng, W X Tang
1School of Physics, Monash University, Victoria 3800, Australia.
Abstract:
We discuss a new interpretation of mirror electron microscopy (MEM) images, whereby electric field distortions caused by surface topography and/or potential variations are sufficiently large to create caustics in the image contrast. Using a ray-based trajectory method, we consider how a family of rays overlaps to create caustics in the vicinity of the imaging plane of the magnetic objective lens. Such image caustics contain useful information on the surface topography and/or potential, and can be directly related to surface features. Specifically we show how a through-focus series of MEM images can be used to extract the contact angle of a Ga droplet on a GaAs (001) surface.

