The influence of step geometry on the desorption characteristics of O2, D2, and H2O from stepped Pt surfaces.
The influence of step geometry on the desorption characteristics of O2, D2, and H2O from stepped Pt surfaces.
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DOI：
10.1063/1.3407434
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发表时间：
2010-05
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通讯作者：
M. J. T. C. van der Niet;Angela den Dunnen;L. Juurlink;M. Koper
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作者：
M. J. T. C. van der Niet;Angela den Dunnen;L. Juurlink;M. Koper
我们用程序升温脱附的方法比较了O（2）、D（2）和H（2）O在Pt（533）和Pt（553）表面的脱附特性。两个表面都由四个原子宽的（111）阶地组成，这些阶地被不同台阶几何形状的单原子台阶中断：分别为（100）和（110）。我们发现，解吸的影响显着的步骤网站和这些网站的几何形状的存在。一般来说，分子和原子被认为是更强烈地结合到台阶网站比梯田网站。我们从Pt（553）得到的D（2）脱附数据为这一普遍看法提供了一个反常的反例，因为该表面上的D原子似乎被平台位束缚得更强。我们还表明，这是不可能的，说一个先验的步骤几何将结合原子或分子更强：重组解吸O原子结合更强的（100）位，而H（2）O分子结合更强的（110）位。此外，受台阶存在影响的吸附原子或分子的量对于不同的物质是不同的，如从O（2）（O）的大约1：1.3、D（2）（D）的大约1：3和H（2）O的大约1：1的各种台阶：平台比中显而易见的。这表明，与氘相反，更多的氧原子和水分子受到台阶的影响，而不是仅仅根据几何参数所预期的。
We have compared the desorption characteristics of O(2), D(2), and H(2)O from the Pt(533) surface to the Pt(553) surface using temperature programmed desorption. Both surfaces consist of four atom wide (111) terraces interrupted by monoatomic steps of the different step geometries: (100) versus (110), respectively. We find that desorption is influenced significantly by the presence of step sites and the geometry of those sites. In general, molecules and atoms are thought to be bound more strongly to step sites than to terrace sites. Our D(2) desorption data from Pt(553) provide an anomalous counterexample to this common belief since D atoms on this surface appear to be bound stronger by terrace sites. We also show that it is not possible to say a priori which step geometry will bind atoms or molecules stronger: recombinatively desorbing O atoms are bound stronger to (100) sites, whereas H(2)O molecules are bound stronger to (110) sites. Furthermore, the amount of adatoms or molecules that are affected by the presence of steps varies for the different species, as is evident from the various step: terrace ratios of approximately 1:1.3 for O(2) (O), approximately 1:3 for D(2) (D), and approximately 1:1 for H(2)O. This indicates that, in contrast to deuterium, more oxygen atoms and water molecules are affected by the presence of steps than would be expected on geometrical arguments alone.