J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
Chemistry. 2012 Oct 22;18(43):13877-84. doi: 10.1002/chem.201202114. Epub 2012 Sep 13.
The Raman spectra of two-layered graphene on a silicon substrate were studied in the temperature range from 298 to 1073 K in an inert atmosphere. Isotopic engineering was used to fabricate two-layer graphene specimens containing (13)C atoms in the top layer and (12)C atoms in the bottom layer, which allowed the behavior of each particular layer to be distinguished as a function of temperature. It is demonstrated that the top layer exhibits much lower Raman temperature coefficients than the bottom one for both the G and the G' modes. We suggest that the changes in the Raman spectra of graphene observed during thermal cycling are predominantly caused by a superposition of two effects, namely, the mechanical stress in graphene exerted by the substrate and the intrinsic changes in the graphene lattice caused by the temperature itself. The top graphene layer is proposed to be more relaxed than the bottom graphene layer and thus reflects almost exclusively the temperature variations as a freestanding graphene layer would.
在惰性气氛中，研究了硅衬底上双层石墨烯的拉曼光谱，温度范围从 298 到 1073 K。同位素工程用于制备双层石墨烯样品，顶层含有 (13)C 原子，底层含有 (12)C 原子，这使得可以区分每个特定层的行为随温度的变化。结果表明，对于 G 和 G' 模式，顶层的拉曼温度系数都明显低于底层。我们认为，在热循环过程中观察到的石墨烯拉曼光谱的变化主要是由两个效应的叠加引起的，即衬底对石墨烯的机械应力和温度本身引起的石墨烯晶格的固有变化。提出顶层石墨烯比底层石墨烯更松弛，因此几乎完全反映了自由-standing 石墨烯层的温度变化。
