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A STRUCTURAL STUDY OF PD/CU(100) SURFACE ALLOYS

TitleA STRUCTURAL STUDY OF PD/CU(100) SURFACE ALLOYS
Publication TypeJournal Article
Year of Publication1995
AuthorsPope, TD, Vos, M, Tang, HT, Griffiths, K, Mitchell, IV, Norton, PR, Liu, W, Li, YS, Mitchell, KAR, Tian, ZJ, Black, JE
JournalSurface Science
Volume337
Pagination79-91
Date PublishedAug
Type of ArticleArticle
ISBN Number0039-6028
Keywords(MEIS), ABSORPTION FINE-STRUCTURE, ADSORPTION, CU(100), DIFFRACTION, GROWTH, HYDROGEN, ION-SCATTERING, LOW ENERGY ELECTRON DIFFRACTION (LEED), LOW-ENERGY ELECTRON, MEDIUM ENERGY ION SCATTERING, molecular dynamics, RECONSTRUCTION, SPECTROSCOPY, surface structure, THERMAL DESORPTION, ULTRATHIN PD FILMS
Abstract

The structures formed by one-half and one monolayer (ML) of Pd evaporated onto Cu(100) at 300 K were studied by low energy electron diffraction (LEED), medium energy ion scattering (MEIS), thermal desorption spectroscopy (TDS), and embedded atom method (EAM) calculations. In the half monolayer case, the LEED I(E) curves are consistent with the established c(2 x 2) surface alloy model. The MEIS data, however, suggest that a fraction of the Pd (similar to 1/4) is in ’’second layer’’ sites, in agreement with previous LEIS, TDS and XPS forward scattering measurements. The EAM simulations support the formation of alloy islands, providing a mechanism for the covering of some Pd atoms. As the deposition proceeds, however, this island formation is indicated to occur preferentially over clean copper. In the one monolayer case, a p(2 x 2)-p4g LEED pattern is observed. Analysis of the I(E) curves suggests that this arises from (100) Pd packed above the c(2 x 2) alloy. EAM calculations confirm the stability of this model. Evidence from MEIS and TDS, however, shows that the one monolayer surface as prepared in this work is inhomogeneous. c(2 x 2) and Cu rich surface domains exist in addition to those having the p4g Pd/c(2 x 2)PdCu structure.

URL<Go to ISI>://A1995RQ74900017