The surface of 6 to 7 monolayer thick fcc Fe films grown at room temperature on a Cu(100) substrate was characterized by scanning tunnelling microscopy and low energy electron diffraction. The scanning tunnelling microscopic images exhibited a p4g(2 x 2) structure at 5 and 80K, but not at 300K. low-energy electron diffraction, however, indicated an expansion of the interlayer distance and lateral distortions of similar magnitude at both 150 and 300K. No evidence for a significant change of the surface structure was detected by a low-energy electron diffraction spot profile analysis between 150 and 300K. The apparent absence of the reconstruction in the scanning tunnelling microscopic images at 300K was attributed to surface dynamics caused by domain boundary motion. The particular surface structure with bond angles and distances similar to bcc Fe suggested a driving force of the reconstruction which was similar to that operative in the fcc-to-bcc transition of bulk Fe. Dosing with less than 5 L H2 decorated the p4g(2 x 2) surface reconstruction, while higher hydrogen doses transformed the surface reconstruction to p(2 x 1).

Reconstruction of the Clean and H Covered “Magnetic Live Surface Layer” of Fe Films Grown on Cu(100). A.Biedermann, R.Tscheliessnig, C.Klein, M.Schmid, P.Varga: Surface Science, 2004, 563[1-3], 110-26