THE STRUCTURE OF THIN EPITAXIAL FE FILMS ON CU(100) IN THE TRANSITION RANGE FCC-]BCC

The structure of epitaxial layers of Fe on Cu(100) is investigated in the coverage range near 10 monolayers where a structural transition from fcc(100) to bcc(110) proceeds in the film with increasing coverage. By measurement and full dynamical analysis of low energy electron diffraction intensities we demonstrate that the resulting bcc(110) structure of the film is fully unstrained and exhibits practically po multilayer relaxation. So it is structurally identical to the (110) surface of bulk iron samples. For the transition range we show that fcc(100) and bcc(110) domains coexist on the surface. Also, we give arguments that the surface reconstruction found earlier for the fcc(100) phase may be understood as a precursor for the transition to bcc(110).