Renovation Center of Instruments for Science Education and Technology, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 560-0047, Japan.
J Chem Phys. 2012 Mar 7;136(9):094704. doi: 10.1063/1.3690019.
Steps are known to be often the active sites for the dissociation of O(2) molecules and the nucleation sites of oxide films since they provide paths for subsurface migration and oxygen incorporation. In order to unravel the effect of their morphology on the oxidation of Cu surfaces, we present here a detailed investigation of the O(2) interaction with Cu(511) and compare it with previous results for Cu(410), a surface exhibiting terraces of similar size and geometry but different step morphology. As for Cu(410) we find, by x-ray photoemission spectroscopy performed with synchrotron radiation, that Cu(2)O formation gradually starts above half a monolayer oxygen coverage and that the ignition of oxidation can be lowered to room temperature by dosing O(2) via a supersonic molecular beam at hyperthermal energy. The oxidation rate for Cu(511) comes out to be lower than for Cu(410) at normal incidence, about the same when the O(2) molecules impinge towards the ascending step rise, but higher when they hit the surface along trajectories even slightly inclined towards the descending step rise. These findings can be rationalized by a collision induced absorption mechanism.
台阶通常是 O(2)分子离解的活性中心和氧化物薄膜成核的位置，因为它们提供了亚表面迁移和氧掺入的途径。为了揭示其形态对 Cu 表面氧化的影响，我们在这里详细研究了 O(2)与 Cu(511)的相互作用，并将其与之前关于 Cu(410)的结果进行了比较，Cu(410)是一个具有相似大小和几何形状但台阶形态不同的表面。与 Cu(410)一样，我们通过使用同步辐射的 X 射线光电子能谱发现，Cu(2)O 的形成在超过半单层氧覆盖度时逐渐开始，并且通过超热分子束以超热能量注入 O(2)可以将氧化的引发降低到室温。对于 Cu(511)，正常入射时的氧化速率比 Cu(410)低，当 O(2)分子朝着上升台阶的上升方向撞击时，大致相同，但当它们沿着稍微朝向下降台阶上升方向倾斜的轨迹撞击表面时，氧化速率更高。这些发现可以通过碰撞诱导吸收机制来合理化。
