The sample surface must be extremely clean for effective RHEED experiments. Contaminants on the sample surface interfere with the electron beam and degrade the quality of the RHEED pattern. RHEED users employ two main techniques to create clean sample surfaces. Small samples can be cleaved in the vacuum chamber prior to RHEED analysis. The newly exposed, cleaved surface is analyzed. Large samples, or those that are not able to be cleaved prior to RHEED analysis can be coated with a passive oxide layer prior to analysis. Subsequent heat treatment under the vacuum of the RHEED chamber removes the oxide layer and exposes the clean sample surface.
... Adsorptions occur only on well-defined sites of the sample surface (one per molecule) 2 ... the heat of adsorption at the solid sample surface 4.3 ... equivalent to the sample being surrounded by a liquid phase) Let us consider a given amount of solid sample in a controlled atmosphere ...
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—Henry David Thoreau (18171862)
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