LOW-TEMPERATURE P2MG (2 X-1) STRUCTURE OF ULTRATHIN EPITAXIAL-FILMS FE/CU(100)

The reconstructed low-temperature p2mg (2 x 1) phase of the epitaxial system Fe/Cu(100) is structurally investigated by means of low-energy electron diffraction (LEED). Special emphasis is also put on the determination of the number of iron layers both within the structural search by LEED as well as by AES, MEED and quartz crystal microbalance. We find best agreement for the investigated film for a thickness of about 6 ML, which corrects earlier results. Except for the top layer iron atoms reside in nearly ideal fcc positions given by the Cu lattice. The top layer is reconstructed such that adjacent close-packed iron rows are shifted antiparallel with respect to each other by 0.14 angstrom. This shift puts the first-layer spacing to 1.88 angstrom corresponding to an expansion of 6% (4%) with respect to the fcc-iron (copper) bulk spacing.