Structures of ultra-thin Fe overlayers on a Rh(001) surface

• Published in: Surface science 1993-03, Vol.283 (1), p.338-343
• Main Authors: Egawa, Chikashi, Tezuka, Yasuyuki, Oki, Shoichi, Murata, Yoshitada
• Format: Article
• Language: English
• Subjects: Applied sciences; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Metals. Metallurgy; Physics; Solid surfaces and solid-solid interfaces; Surface and interface dynamics and vibrations; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thin film structure and morphology
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/0039-6028(93)91000-F

The structures of ultra-thin Fe overlayers grown on a Rh(001) surface have been investigated by low energy electron diffraction (LEED) and angle-resolved Auger electron spectroscopy (ARAES) for film coverages of 0–20 ML and in a wide temperature range of 100–1300 K. Deposition at 350 K formed a pseudomorphic (1 × 1) fcc (001) structure of Fe for film thicknesses of 1–5 ML. New subspots due to a (2√2 × √2)R45° superstructure appeared at 6 ML and became streaky at 8 ML. The main spots then splitted into four in the respective [110] direction corresponding to four faceted planes above 10 ML. The facet structure was observed in a wide coverage range of 10–20 ML. It is confirmed by ARAES that Fe films have an fcc structure over the whole coverage range. The deviation from the pseudomorphic structure above 6 ML is interpreted to be caused by the lattice mismatch (5.7%) between Fe and Rh in the fcc structure. Annealing of these Fe films up to 1300 K caused sequential LEED patterns of (1 × 1) with a high background (1–5 ML) or streaky along the [100] direction (6–8 ML), c(2 × 2) and finally the (1 × 1) structure. From the change in Auger intensities the c(2 × 2) structure observed above 1100 K corresponding to a surface Fe coverage of 0.5 remained after the desorption of Fe overlayers.