LOW ENERGY ELECTRON DIFFRACTION

The spot profile analysis low energy electron diffraction (SPA-LEED) instrument it is a LEED with the advantages of very high dynamic range and very high lateral (thus reciprocal space) resolution. It is thus particularly well suited for high resolution, high dynamic range measurements of LEED spot profiles for detailed analysis of the spot shape (hence its name), which allows to derive quantitative information on roughness, defects, etc. impossible to infer from other methods

The SPA-LEED combines two electrostatic deflection systems to bend the trajectories of the incoming electron beam (originating at the electron gun) on an S-shaped path onto the sample, as well as that of the diffracted electrons in the same fashion on the way back to a single electron detector.

The deflection of incoming and diffracted trajectory leads to a favorable Ewald construction with almost twice the length of the (k_f - k_i) vector and thus a larger accessible k_// range and less Ewald sphere curvature in comparison to an optical LEED instrument.

Our SPA-LEED is mounted on the Analysic chamber of the Modular facility for Oxide Deposition and Analysis. It is able to study the surface of in-situ grown film and it allows also the possibility of sample treatment in ultra high vacuum up to 900°C.