Ordered ultra-thin cerium oxide overlayers on Pt(111) single crystal surfaces studied by LEED and XPS

被引：135
|
作者：
Schierbaum, KD [1 ]
机构：
[1] Univ Tubingen, Inst Phys & Theoret Chem, D-72076 Tubingen, Germany
来源：
SURFACE SCIENCE | 1998年 / 399卷 / 01期
关键词：
catalysis; cerium oxides; growth; low-energy electron diffraction; platinum; surface defects; X-ray photoelectron spectroscopy;
D O I：
10.1016/S0039-6028(97)00808-X
中图分类号：
O64 [物理化学（理论化学）、化学物理学];
学科分类号：
070304 ; 081704 ;
摘要：
The preparation of ordered ultra-thin cerium oxide overlayers on nonreconstructed Pt(111) single crystal surfaces is reported. Thin electron-beam evaporated CeO2 layers (d=21 Angstrom) decompose during heating in ultra-high vacuum (UHV) at T=1000 K and form domains of ordered PtCe2 and PtCe3 surface alloys. They exhibit a (2x2)+(2x2)R30 degrees pattern in low-energy electron diffraction (LEED). Oxidation under thermodynamically controlled conditions (p(O2)=6x10(-5) mbar, T=1000 K) leads to a CeO2 layer (d=6.3 Angstrom) which forms a (1.4x1.4) superstructure on Pt(111) 1x1. X-ray photoemission spectra (XPS) reveal a high concentration of Ce3+ ions. Deconvolution yields a deviation, x, of 0.21 from ideal stoichiometry. The deviation is lower (x=0.14) for an increased layer thickness (d=24 Angstrom) whilst the CeO2-x remains ordered with unchanged epitaxial relationships with respect to Pt(111). (C) 1998 Elsevier Science B.V.
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页码：29 / 38
页数：10
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