Buckling reversal of the Si(111) bilayer termination of 2-dimensional ErSi2 upon H dosing

E-ISSN： 1286-4854|38|5|359-364

ISSN： 0295-5075

Source： EPL (EUROPHYSICS LETTERS), Vol.38, Iss.5, 2010-03, pp. : 359-364

Disclaimer: Any content in publications that violate the sovereignty, the constitution or regulations of the PRC is not accepted or approved by CNPIEC.

Previous Menu Next

Abstract

Hydrogen-induced reconstruction of 2-dimensional (2D) $\rm ErSi_2$ epitaxially grown on Si(111) is studied by Auger-electron diffraction (AED) and low-energy electron diffraction (LEED). The intensity of the Er MNN Auger line is measured vs. polar angle along the $[1\,{-2}\,1]$ and $[{-1}\,2\,{-1}]$ azimuths for clean andH-saturated $(1\times 1)$ $\rm ErSi_2$ silicides. The atomic structure of clean2D silicide, previously established by AED as well as other techniques,consists of a hexagonal monolayer of Er located underneath a buckled Si layercomparable to the Si(111) substrate double layers. Moreover, for clean 2D $\rmErSi_2$ only the B-type orientation is observed, i.e. the buckled Sitop layer is always rotated by $180^\circ$ around the surface normal relativeto the relevant double layers of the substrate. After atomic H saturation, AEDreveals drastic changes in the silicide structure involving a major mostremarkable reconstruction of the Si bilayer termination. The latter is foundto switch from B-type to A-type orientation upon H dosing, i.e. H-saturated 2D $\rm ErSi_2$ exhibits a buckled Si top layer oriented in the sameway as the substrate double layers. A comparison with single scattering clustersimulations demonstrates that the latter phenomenon is accompanied by a largeexpansion of the Er-Si interlayer spacing close to 0.3 Å.