Structure of ultrathin films of Fe on Cu{111} and Cu{110}

Abstract

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