Co ultra-thin films on Pt(111) and Co-Pt alloying: a LEED, Auger and synchrotron x-ray diffraction study

Citation
R. Baudoing-savois et al., Co ultra-thin films on Pt(111) and Co-Pt alloying: a LEED, Auger and synchrotron x-ray diffraction study, J PHYS-COND, 11(43), 1999, pp. 8355-8375
Citations number
47
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science
Journal title
JOURNAL OF PHYSICS-CONDENSED MATTER
ISSN journal
09538984 → ACNP
Volume
11
Issue
43
Year of publication
1999
Pages
8355 - 8375
Database
ISI
SICI code
0953-8984(19991101)11:43<8355:CUFOPA>2.0.ZU;2-Q
Abstract
Co ultra-thin Alms deposited on Pt(111) are analysed in detail, using LEED, Auger spectroscopy and x-ray diffraction. The growth is quasi layer-by-lay er up to about 3 ML. Co grows as islands, in incoherent epitaxy with the Pt substrate; the corresponding satellites are observed even for coverages as low as 0.12 ML. The Co in-plane parameter is very close to its own bulk va lue. For thicker films, deposited at room temperature, face centerd cubic ( fcc), twin fee and hexagonal close packed (hcp) fractions are present. Using x-ray diffraction, we followed in real-time the transformations of th e deposited film upon annealing. The role of the Co film structure (which d epends on the film thickness) is predominant. For 'thick' films (greater th an or equal to 6 ML) a sharp transition occurs around 670 K: below this tem perature, the film is mainly hcp so that it allows little Pt incorporation, while above it turns to a very homogeneous fee alloy of composition close to Pt60Co40. Segregation phenomena were analysed and found similar to those occurring at the surface of the corresponding bulk alloys.