A potential way to tune the electronic band structure of graphene is to intercalate foreign atoms in the interface between graphene and substrate. However, such an intercalate layer covered by graphene is difficult to directly study with microscopic probes, and relatively little is known about its crystal and electronic structures. In this work, we study epitaxial graphene on SiC(0001) intercalated by bismuth atoms by means of angle-resolved photoemission spectroscopy. We reveal the electronic band structure of Bi-intercalate layers, from which we could identify two distinct phases, one is metallic and the other is insulating. The metallic phase composed of closely packed Bi atoms shows nearly free electron bands that are repeated to follow the period of SiC(0001)-(1 $$\times $$ × 1). The lower coverage insulating phase shows characteristic flat bands in the period of SiC(0001)-( $$\sqrt{3} {\times } \sqrt{3}$$ 3 × 3 )R30 $$^\circ $$ ∘ with respect to the surface lattice constant of SiC(0001). Even though there exists such two distinct phases in the Bi intercalate layer, the doping level of graphene is found to vary rather continuously with the coverage of Bi. Based on the observed band structures and Bi 5 d core-level spectra, we suggest a structural model for the metallic and insulating phases of Bi-terminated SiC(0001).

中文翻译：

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石墨烯和碳化硅中双嵌入层的电子能带结构(0001)

调整石墨烯电子能带结构的一种潜在方法是在石墨烯和基板之间的界面中插入外来原子。然而，这种被石墨烯覆盖的嵌入层很难用微观探针直接研究，对其晶体和电子结构知之甚少。在这项工作中，我们通过角分辨光电子发射光谱研究了由铋原子插入的 SiC(0001) 上的外延石墨烯。我们揭示了双插层的电子能带结构，从中我们可以识别出两种不同的相，一种是金属相，另一种是绝缘相。由紧密堆积的 Bi 原子组成的金属相显示出几乎自由的电子带，这些带重复遵循 SiC(0001)-(1 $$\times $$ × 1) 的周期。下覆盖绝缘相在 SiC(0001)-( $$\sqrt{3} {\times } \sqrt{3}$$ 3 × 3 )R30 $$^\circ $$ ∘关于 SiC(0001) 的表面晶格常数。尽管在 Bi 嵌入层中存在这样两个不同的相，但发现石墨烯的掺杂水平随着 Bi 的覆盖而连续变化。基于观察到的能带结构和 Bi 5 d 核能级光谱，我们提出了一种双端接 SiC(0001) 金属相和绝缘相的结构模型。发现石墨烯的掺杂水平随着 Bi 的覆盖而连续变化。基于观察到的能带结构和 Bi 5 d 核能级光谱，我们提出了一种双端接 SiC(0001) 金属相和绝缘相的结构模型。发现石墨烯的掺杂水平随着 Bi 的覆盖而连续变化。基于观察到的能带结构和 Bi 5 d 核能级光谱，我们提出了一种双端接 SiC(0001) 金属相和绝缘相的结构模型。