Abstract
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 monolayers (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 form a (2 × 2) superstructure after exposing the Pd-Ni-Pd(111) surface at 590 K to 350 L O2. The oxygen-induced segregation of Ni is consistent with predictions from density functional theory (DFT) calculations.
Original language | English (US) |
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Pages (from-to) | 56-64 |
Number of pages | 9 |
Journal | Surface Science |
Volume | 646 |
DOIs | |
State | Published - Apr 2016 |
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Surfaces and Interfaces
- Surfaces, Coatings and Films
- Materials Chemistry
Keywords
- Bimetallic surface
- DFT
- LEIS
- STM
- Subsurface monolayer
- Surface segregation