Cobalt grows initially on Cu(111) in the form of bilayer islands with the shape of triangles of alternate orientation. This is probably related to the initial stacking sequence of the Co layers. The islands do not coalesce upon further deposition and the resulting film, although epitaxial and crystalline to the extent tested by diffraction techniques, is, actually, granular. Thus, microscopic evidence is provided for the existence of an intrinsic defect, namely, twinned fcc crystallites and their associated grain boundaries, which may be the much sought cause of discrepancy on antiferromagnetic coupling data in Co/Cu(111) superlattices grown in ultrahigh vacuum.

• Received 19 February 1993

DOI:https://doi.org/10.1103/PhysRevB.47.13043