St. Petersburg State University , 7/9 Universitetskaya nab., St. Petersburg, 199034, Russia.
Ioffe Physical Technical Institute , St. Petersburg, 194021, Russia.
ACS Nano. 2017 Jun 27;11(6):6336-6345. doi: 10.1021/acsnano.7b02686. Epub 2017 May 18.
Regardless of the widely accepted opinion that there is no Raman signal from single-layer graphene when it is strongly bonded to a metal surface, we present Raman spectra of a graphene monolayer on Ni(111) and Co(0001) substrates. The high binding energy of carbon to these surfaces allows formation of lattice-matched (1 × 1) structures where graphene is significantly stretched. This is reflected in a record-breaking shift of the Raman G band by more than 100 cm relative to the case of freestanding graphene. Using electron diffraction and photoemission spectroscopy, we explore the aforementioned systems together with polycrystalline graphene on Co and analyze possible intercalation of oxygen at ambient conditions. The results obtained are fully supported by Raman spectroscopy. Performing a theoretical investigation of the phonon dispersions of freestanding graphene and stretched graphene on the strongly interacting Co surface, we explain the main features of the Raman spectra. Our results create a reliable platform for application of Raman spectroscopy in diagnostics of chemisorbed graphene and related materials.
尽管普遍认为当单层石墨烯与金属表面强烈结合时，它不会产生拉曼信号，但我们呈现了单层石墨烯在 Ni(111)和 Co(0001)衬底上的拉曼光谱。碳与这些表面的高结合能允许形成晶格匹配的(1 × 1)结构，其中石墨烯被显著拉伸。这反映在拉曼 G 带的惊人位移上，与自由-standing 石墨烯相比，超过了 100 cm。使用电子衍射和光电子能谱，我们一起探索了上述系统以及 Co 上的多晶石墨烯，并分析了在环境条件下可能的氧插入。拉曼光谱完全支持所得到的结果。通过对自由-standing 石墨烯和在强烈相互作用的 Co 表面上拉伸的石墨烯的声子色散进行理论研究，我们解释了拉曼光谱的主要特征。我们的结果为拉曼光谱在化学吸附石墨烯和相关材料的诊断中的应用提供了可靠的平台。
