The atomic structure of thin epitaxial erbium silicides on Si(111) substrates has been studied in situ by means of surface X-ray diffraction and medium-energy ion scattering. In the sub-monolayer range, a two-dimensional (2D) silicide is formed within a 1x1 unit cell, with the Er atoms occupying T4 sites and a Si bilayer on top which is 180º rotated with respect to the bulk (B-type). Silicide layers with a thickness of 3 monolayers exhibit a regular network of Si vacancies which release the compressive strain of the graphite-like Si layers between adjacent Er layers. This results in a √3 x √3 R30º unit cell, in which 3 out of 5 Si atoms are displaced towards the vacancy, and in which 3 Er atoms relax away from the vacancy.

Materials Research Society
B.G. Demczyk , E. Garfunkel , B.M. Clemens , E.D. Williams , J.J. Cuomo

Lohmeier, M, Huisman, W.J, ter Horst, G, Zagwijn, P.M, Nishiyama, A, Nicklin, C.L, … Vlieg, E. (1995). Atomic structure of ultrathin erbium silicides on Si(111). In B.G Demczyk, E Garfunkel, B.M Clemens, E.D Williams, & J.J Cuomo (Eds.), Evolution of ThinFilm and Surface Structure and Morphology (pp. 281–286). Materials Research Society.