Stability of Pt-Modified Cu(111) in the Presence of Oxygen and Its Implication on the Overall Electronic Structure
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- 作者：Henrik 脰berg ; Toyli Anniyev ; Aleksandra Vojvodic ; Sarp Kaya ; Hirohito Ogasawara ; Daniel Friebel ; Daniel J. Miller ; Dennis Nordlund ; Uwe Bergmann ; Mathias P. Ljungberg ; Frank Abild-Pedersen ; Anders Nilsson ; Lars G. M. Pettersson
- 刊名：The Journal of Physical Chemistry C
- 出版年：2013
- 出版时间：August 15, 2013
- 年：2013
- 卷：117
- 期：32
- 页码：16371-16380
- 全文大小：457K
- 年卷期：v.117,no.32(August 15, 2013)
- ISSN：1932-7455
文摘
The electronic structure and stability of Cu(111)-hosted Pt overlayers with and without the presence of atomic oxygen have been studied by means of core-level spectroscopy and density functional theory (DFT). Because of lattice mismatch, Pt(111) overlayers grown on Cu(111) are compressively strained, and hard X-ray photoelectron spectroscopy together with Pt L3-edge X-ray absorption spectroscopy (XAS) reveals a pronounced downshift of the Pt d-band owing to the increased overlap of the d-orbitals, an effect also reproduced theoretically. Exposure to oxygen severely alters the surface composition; the O鈥揅u binding energy largely exceeds that of O鈥揚t, and DFT calculations predict surface segregation of Cu atoms. Comparing the adsorbate electronic structure for O on unstrained Pt(111) with that of O on Pt-modified Cu(111) using O K-edge XAS and X-ray emission spectroscopy salient differences are observed and calculations show that Cu-segregation to the topmost layer is required to reproduce the measured spectra. It is proposed that O is binding in a hollow site constituted by at least two Cu atoms and that up to 75% of the Pt atoms migrate below the surface.