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利用低能电子衍射、同步辐射光电子能谱和X射线光电子谱原位、系统地研究Ru(0001)单晶表面外延生长CeO2(111)薄膜表面形貌、电子结构、化学元素组成和热稳定性。在超高真空条件下和氧气氛(1.33×10-5Pa)中,在Ru(0001)单晶衬底表面上热蒸发金属Ce,反应生成的CeO2薄膜呈外延生长。结果表明,高覆盖度条件下,生成的CeO2(111)薄膜是连续的,且完全覆盖衬底,只有1.4×1.4结构的衍射花样。在4.5 nm完全氧化的CeO2(111)薄膜价带谱中,3~8 eV之间展宽的谱峰归属于O 2p能级,其中,4.1和6.5 eV位置的2个谱峰分别对应于O 2p轨道与Ce 4f0和Ce 5d轨道形成的杂化态峰。当样品表面升温到700℃时,4.1 eV处的Ce4+(4f0)峰略微减弱,并且在1.6 eV处出现了Ce3+(4f1)峰,说明样品表面已经有部分Ce4+转化成Ce3+,发生了还原反应。若进一步提升样品的退火温度,则CeO2的还原程度也越高。
The surface morphology, electronic structure, chemical element composition and thermal stability of CeO2 (111) thin film grown on Ru (0001) single crystal surface were studied systematically by using low energy electron diffraction, synchrotron radiation photoelectron spectroscopy and X-ray photoelectron spectroscopy. The metal Ce was thermally evaporated on the surface of the Ru (0001) single crystal substrate under an ultra-high vacuum and in an oxygen atmosphere (1.33 × 10 -5 Pa), and the CeO2 film was epitaxially grown. The results show that the CeO2 (111) films are continuous and cover the substrate completely with only 1.4 × 1.4 diffraction pattern under high coverage. In the 4.5 nm fully oxidized CeO2 (111) thin film, band broadening between 3 and 8 eV belongs to the O 2p level, where the two peaks at 4.1 and 6.5 eV correspond to O 2p Orbital of Ce 4f0 and Ce 5d orbitals. When the sample surface is heated to 700 ℃, the peak of Ce4 + (4f0) at 4.1 eV slightly weakens, and the peak of Ce3 + (4f1) appears at 1.6 eV, indicating that some Ce4 + has been converted to Ce3 + on the sample surface and a reduction reaction has occurred. If you further increase the annealing temperature of the sample, the higher the reduction of CeO2.