He Yunbin, Seitsonen Ari P, Over Herbert
Physikalisch Chemisches Institut, Justus-Liebig-Universität Giessen, Heinrich-Buff-Ring 58, 35392 Giessen, Germany.
J Chem Phys. 2006 Jan 21;124(3):034706. doi: 10.1063/1.2159489.
Ultrathin rhodium films with a thickness ranging from 1 to a few monolayers were deposited on a single-crystal Ru(0001) surface in order to investigate the oxidation behavior of ultrathin epitaxial films on a dissimilar substrate. It is found that rhodium grows on Ru(0001) initially layer by layer, adapting the in-plane lattice parameters of Ru(0001). When exposing Rh films to oxygen environment (approximately 4.8 x 10(6) L O2 exposure) at 660 K, 2-4 ML Rh films form a surface oxide composed of (9 x 9) O-Rh-O trilayers. Quite in contrast, oxidation of the 1 ML RhRu(0001) film leads to a poorly ordered oxide with a rutile structure reminiscent of RuO2(110) on Ru(0001). The oxidized 1 ML RhRu(0001) film contains much more oxygen than the oxidized thicker Rh films. Lower temperatures (535 K) and high doses of oxygen lead to a (1 x 1)-O overlayer on the 1 ML RhRu(0001) surface, whose atomic geometry resembles closely that of the (1 x 1)-O phase on clean Ru(0001).
为了研究超薄外延膜在异种衬底上的氧化行为，在单晶Ru(0001)表面沉积了厚度从1到几个单分子层的超薄铑膜。发现铑最初在Ru(0001)上逐层生长，适应Ru(0001)的面内晶格参数。当在660 K下将铑膜暴露于氧气环境（约4.8×10(6) L O2暴露量）时，2 - 4 ML的铑膜形成由(9×9) O - Rh - O三层组成的表面氧化物。相比之下，1 ML Rh/Ru(0001)膜的氧化导致形成一种有序性较差的具有金红石结构的氧化物，使人联想到Ru(0001)上的RuO2(110)。氧化后的1 ML Rh/Ru(0001)膜比氧化后的较厚铑膜含有更多的氧。较低温度（535 K）和高剂量的氧气会在1 ML Rh/Ru(0001)表面形成(1×1) - O覆盖层,其原子几何结构与清洁Ru(0001)上的(1×1) - O相非常相似。
