Surface potentials of (111), (110) and (100) oriented CeO2−x thin films
Surface potentials of (111), (110) and (100) oriented CeO2−x thin films
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DOI：
10.1016/j.apsusc.2016.03.091
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发表时间：
2016-07
影响因子：
6.7
通讯作者：
Hans F. Wardenga;A. Klein
中科院分区：
文献类型：
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作者：
Hans F. Wardenga;A. Klein
用射频磁控溅射法从未掺杂的CeO 2靶上制备了CeO 2薄膜。(111)分别在Al 2 O3（0001）/Pt（111）、MgO（110）/Pt（110）和SrTiO 3：Nb（100）衬底上制备了（110）和（100）取向的薄膜。用X射线衍射分析验证了外延生长。通过原位光电子能谱分析了薄膜的电离势、功函数、费米能级位置和表面Ce 3+浓度与晶体取向、沉积条件和还原性和氧化性气氛中的沉积后处理的关系。我们观察到一个非常高的变化的功函数和电离势超过2 eV的所有表面取向，而费米能级变化仅为0.3 eV的能隙内。功函数一般随Ce ~（3+）表面浓度的增加而降低，但即使在强氧化处理后，仍保持较高的Ce ~（3+）浓度。这与表面下氧空位的存在有关。
Differently oriented CeO2thin films were prepared by radio frequency magnetron sputter deposition from a nominally undoped CeO2target. (111), (110) and (100) oriented films were achieved by deposition onto Al2O3(0001)/Pt(111), MgO(110)/Pt(110) and SrTiO3:Nb(100) substrates, respectively. Epitaxial growth is verified using X-ray diffraction analysis. The films were analyzed byin situphotoelectron spectroscopy to determine the ionization potential, work function, Fermi level position and Ce3+concentration at the surface in dependence of crystal orientation, deposition conditions and post-deposition treatment in reducing and oxidizing atmosphere. We observed a very high variation of the work function and ionization potential of more than 2 eV for all surface orientations, while the Fermi level varies by only 0.3 eV within the energy gap. The work function generally decreases with increasing Ce3+surface concentration but comparatively high Ce3+concentrations remain even after strongly oxidizing treatments. This is related to the presence of subsurface oxygen vacancies.