Observation of Surface Micro-Structures by Micro-Probe Reflection High-Energy Electron Diffraction

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Abstract
A new micro-probe reflection high-energy electron diffraction technique has been developed for observing micro-structures on crystal surfaces. In this technique, an electron beam of diameter 20 nm at a beam current of 8 nA and a beam angular divergence of 2 mrad has been achieved by using a field emission gun, making it possible to obtain bright, sharp diffraction patterns from surface micro-areas. A diffraction spot on a fluorescent screen is focused on an apperture by an optical lens; and part of the intensity is used as a signal to produce a scanning electron microscope image. This image is very sensitive to changes in surface crystallographic orientation, and can show areas in which the orientation change is of the order of 0.1 mrad. When the technique was used to observe Si(111) surfaces and metal-deposited Si(111) surfaces, image contrasts caused by screw dislocations, atomic steps and domain structures on the surfaces were obtained.