Composition, structure and stability of surfaces formed by Ni deposition on Pd(111)

SURFACE SCIENCE

卷:646

Article

Fu, Jie¹  Yang, Xiaofang^1,2,4  Menning, Carl A.²  Chen, Jingguang G.³  Koel, Bruce E.¹ 

[1] Princeton Univ, Dept Chem & Biol Engn, Princeton, NJ 08544 USA

[2] Univ Delaware, Dept Chem Engn, Catalysis Ctr Energy Innovat, Newark, DE 19716 USA

[3] Columbia Univ, Dept Chem Engn, New York, NY 10027 USA

[4] Brookhaven Natl Lab, Dept Chem, Upton, NY 11973 USA

关键词: Bimetallic surface;    Subsurface monolayer;    Surface segregation;    STM;    LEIS;    DFT;   

DOI  :  10.1016/j.susc.2015.05.026

来源: Elsevier

【 摘 要 】

Surface composition and structure of deposited Ni ultrathin films grown on a Pd(111) surface and their thermal stability have been studied using Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), low energy ion scattering (LEIS) and scanning tunneling microscopy (STM). In experiments where up to 2 mono layers (ML) of Ni was deposited onto Pd(111) at 300 K, the initial film growth followed a non-ideal layer-by-layer growth mode, in which the majority of the surface was covered by a single atomic layer of Ni, but the second Ni layer started to appear before the first layer was completed. Annealing the Ni/Pd(111) surface to 600 K caused Ni interdiffusion into subsurface layers and the outermost surface was mainly Pd. This structure, designated as Pd-Ni-Pd(111), was not stable in the presence of surface oxygen. Ni segregated to the topmost surface layer to forth a (2 x 2) superstructure after exposing the Pd-Ni-Pd(111) surface at 590 K to 350 L O-2. The oxygen-induced segregation of Ni is consistent with predictions from density functional theory (DFT) calculations. (C) 2015 Elsevier B.V. All rights reserved.

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