This work investigates the interaction of silicon with ruthenium, extending from Si-defect centers in ruthenium bulk to the adsorption of Si on the Ru(0001) surface. Using density functional theory (DFT) we calculate the interaction energies of up to 2 monolayers (MLs) of Si with this surface, uncovering the initial formation of ruthenium silicide (Ru_xSi_y). Our results demonstrate that Si readily forms substitutional defects (Si_Ru) in bulk ruthenium. These defects are further stabilized on the Ru(0001) surface, resulting in a distinct propensity for forming Ru–Si_Ru mixed layers – which can thus be described by stoichiometry Ru_xSi_y. Overlayers of surface-adsorbed Si adatoms and Ru_xSi_y mixed layers are iso-energetic at 0.5 ML, with the latter becoming increasingly energetically favored at higher Si coverages. We further examine the influence of Ru_xSi_y formation with respect to oxide formation, focusing on coverage-dependent energy differences. Our results show Ru_xSi_y layers are energetically favored with respect to the forming oxide for silicon and oxygen coverages above 1.1 ML, respectively. In addition, the formation of Ru_xSi_y and the subsequent oxidation of Ru and Ru_xSi_y were also investigated experimentally using in situ XPS. This confirmed the DFT prediction, with negligible oxide formation on the Ru_xSi_y sample, whereas the unprotected Ru surface showed extensive RuO₂ formation under the same conditions. Our study not only enhances the understanding of Ru surface chemistry but also suggests a straightforward computational approach for screening the oxidation resistance of surface coatings.

中文翻译：

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RuxSiy 对 Ru（0001） 的覆盖依赖性稳定性：DFT 和 XPS 的比较研究


这项工作研究了硅与钌的相互作用，从钌块体中的 Si 缺陷中心延伸到 Ru（0001） 表面对 Si 的吸附。使用密度泛函理论 （DFT），我们计算了多达 2 个单层 （ML） 的硅与该表面的相互作用能，揭示了钌硅化物 （Ru_xSi_y） 的初始形成。我们的结果表明，Si 很容易在块状钌中形成取代缺陷 （Si_Ru）。这些缺陷在 Ru（0001） 表面上进一步稳定，导致形成 Ru-Si_Ru 混合层的独特倾向——因此可以用化学计量法 Ru_xSi_y 来描述。表面吸附的 Si 吸附原子和 Ru_xSi_y 混合层的外层在 0.5 ML 时具有等能，后者在较高的 Si 覆盖率下越来越受到能量青睐。我们进一步研究了 Ru_xSi_y 形成对氧化物形成的影响，重点关注覆盖依赖性的能量差异。我们的结果表明，对于硅和氧覆盖率高于 1.1 ML，Ru_xSi_y 层在能量上分别受到能量青睐。 此外，还使用原位 XPS 实验研究了 Ru_xSi_y 的形成以及随后的 Ru 和 Ru_xSi_y 的氧化。这证实了 DFT 预测，Ru_xSi_y 样品上的氧化物形成可以忽略不计，而未受保护的 Ru 表面在相同条件下显示出广泛的 RuO₂ 形成。我们的研究不仅增强了对 Ru 表面化学的理解，还提出了一种简单的计算方法来筛选表面涂层的抗氧化性。