The so-called buffer layer (BL) is a carbon rich reconstructed layer formed during the sublimation of SiC (0001). The existence of covalent bonds between some of the carbon atoms in this layer and the underlying silicon atoms makes it different from epitaxial graphene. We report a systematical and statistical investigation of the BL signature and its coupling with epitaxial graphene by Raman spectroscopy. Three different kinds of BLs are studied: bare buffer layer obtained by direct growth (BL 0), interfacial buffer layer situated between graphene and SiC (c-BL 1) and the interfacial buffer layer without graphene above (u-BL 1). To obtain the latter, we develop a mechanical exfoliation of graphene by depositing and subsequently removing an epoxy-based resin or nickel layer. The observed BLs are ordered-like on the whole BL growth temperature range. BL 0 Raman signature may vary from sample to sample but also forms patches on the same terrace. u-BL 1 share similar properties with BL 0 , albeit with more variability. These BLs have a strikingly larger overall intensity than BL with graphene on top. The signal onset on the high frequency side upshifts upon graphene coverage, that cannot be explained by a simple strain effect. Two fine peaks situated at 1235 and 1360 cm-1 are present for epitaxial monolayer while absent for BL and transferred graphene. These findings point to a coupling between graphene and BL.

中文翻译：

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通过拉曼散射和石墨烯剥离解开的缓冲层不均匀性和与外延石墨烯的耦合

所谓的缓冲层（BL）是碳化硅（0001）升华过程中形成的富碳重构层。该层中的一些碳原子与下面的硅原子之间存在共价键，使其不同于外延石墨烯。我们通过拉曼光谱报告了 BL 特征及其与外延石墨烯耦合的系统和统计研究。研究了三种不同类型的 BL：通过直接生长获得的裸缓冲层 (BL 0)、位于石墨烯和 SiC 之间的界面缓冲层 (c-BL 1) 以及上面没有石墨烯的界面缓冲层 (u-BL 1)。为了获得后者，我们通过沉积并随后去除环氧基树脂或镍层来开发石墨烯的机械剥离。观察到的 BL 在整个 BL 生长温度范围内都是有序的。BL 0 拉曼特征可能因样品而异，但也会在同一平台上形成斑块。u-BL 1 与 BL 0 具有相似的特性，尽管具有更多的可变性。这些 BL 的整体强度比顶部有石墨烯的 BL 大得多。高频侧的信号开始随着石墨烯覆盖而上升，这不能用简单的应变效应来解释。外延单层存在两个位于 1235 和 1360 cm-1 的细峰，而 BL 和转移石墨烯不存在。这些发现表明石墨烯和 BL 之间存在耦合。高频侧的信号开始在石墨烯覆盖时上移，这不能用简单的应变效应来解释。外延单层存在两个位于 1235 和 1360 cm-1 的细峰，而 BL 和转移石墨烯不存在。这些发现表明石墨烯和 BL 之间存在耦合。高频侧的信号开始随着石墨烯覆盖而上升，这不能用简单的应变效应来解释。外延单层存在两个位于 1235 和 1360 cm-1 的细峰，而 BL 和转移石墨烯不存在。这些发现表明石墨烯和 BL 之间存在耦合。