Hydrogen-induced reconstruction of 2-dimensional ErSi2 epitaxially grown on Si(111) was studied by Auger electron diffraction and low-energy electron diffraction. The intensity of the Er MNN Auger line was measured vs. polar angle along the [1¯21] and [¯12¯1] azimuths for clean and H-saturated (1 x 1) ErSi2 silicides. The atomic structure of clean 2D silicide, previously established by Auger electron diffraction as well as other techniques, consisted of an hexagonal monolayer of Er located underneath a buckled Si layer comparable to the Si(111) substrate double layers. Moreover, for clean 2D ErSi2 only the B-type orientation was observed, i.e. the buckled Si top layer was always rotated by 180° around the surface normal relative to the relevant double layers of the substrate. After atomic H saturation, Auger electron diffraction revealed drastic changes in the silicide structure involving a major most remarkable reconstruction of the Si bilayer termination. The latter was found to switch from B-type to A-type orientation upon H-dosing, i.e. H-saturated 2D ErSi2 exhibited a buckled Si top layer oriented in the same way as the substrate double layers. A comparison with single scattering cluster simulations demonstrated that the latter phenomenon was accompanied by a large expansion of the Er-Si interlayer spacing close to 0.3Å.

Buckling Reversal of the Si(111) Bilayer Termination of 2-Dimensional ErSi2 upon H Dosing. P.Wetzel, C.Pirri and G.Gewinner: Europhysics Letters, 1997, 38[5], 359-64