STRUCTURE OF ULTRATHIN FILMS OF FE ON CU (111) AND CU (110)

A study of the growth of Fe on Cu{111} and on Cu{110} has been carried out with low-energy electron diffraction (LEED) and Auger electron spectroscopy. We find that on Cu{111}, Fe grows first pseudomorphically as gamma-Fe{111} to a thickness of about five layer equivalents (LE), and then forms six bcc Fe{110} domains rotationally related in the Kurdjumov-Sachs orientation. The pseudomorphic film has the same bulk interlayer spacing, within experimental error, as the Cu{111} substrate (2.08 +/- 0.03 angstrom) and a slightly contracted first interlayer spacing (2.03 +/- 0.03 angstrom). With increasing thickness more and more defects are introduced in the film, but a 13-LE film still produces a good LEED pattern. On Cu{110}, the Fe film grows also pseudomorphically, with the same bulk interlayer spacing as the substrate (1.27 angstrom) and a contracted first interlayer spacing (1.17 angstrom), but a precise structure analysis is not possible because the film has relatively large {111} facets. Defects and disorder increase with film thickness, so that the LEED pattern is practically obliterated when the thickness exceeds about 20 LE.