标题： 在SiC(0001)上的单层和（扭曲）多层石墨烯的外延生长 显示英文标题

标题： Epitaxial growth of mono- and (twisted) multilayer graphene on SiC(0001)

摘要： 为了充分利用石墨烯或其他二维材料的扭曲双层结构，精确控制堆叠层之间的扭转角度至关重要，因为这一参数决定了异质结构的特性。 在此背景下，已报道了一种使用硼嗪作为表面活性分子在SiC(0001)表面上的生长方法，导致形成了高质量的外延石墨烯层，这些层以非常规方式取向，即与基底晶格对齐（G-$R0^\circ$）[Bocquet等人，Phys. Rev. Lett. 125, 106102 (2020)]。 由于G-$R0^\circ$层位于一个缓冲层上，也称为零层石墨烯（ZLG），该层相对于SiC基底旋转了$30^\circ$，并且仍然与其共价键合，因此将ZLG-$R30^\circ$与基底解耦可能导致高质量的扭曲双层石墨烯（tBLG）。 在这里，我们报告了在硼嗪气氛中退火过程中升高温度以实现ZLG-$R30^\circ$的解耦。 虽然这会将ZLG-$R30^\circ$转化为G-$R30^\circ$并从而产生tBLG，但高温下的生长过程不再自我限制，导致表面被不同厚度的石墨烯多层结构覆盖。 我们发现ZLG上有20%的tBLG覆盖率，而在其余表面上，tBLG则位于一个或多个额外的石墨烯层上。 为了仅实现tBLG的完全覆盖，可能通过用合适的原子进行插层等其他解耦方法会更有利。 显示英文摘要

摘要： To take full advantage of twisted bilayers of graphene or other two-dimensional materials, it is essential to precisely control the twist angle between the stacked layers, as this parameter determines the properties of the heterostructure. In this context, a growth routine using borazine as a surfactant molecule on SiC(0001) surfaces has been reported, leading to the formation of high-quality epitaxial graphene layers that are unconventionally oriented, i.e., aligned with the substrate lattice (G-$R0^\circ$) [Bocquet et al. Phys. Rev. Lett. 125, 106102 (2020)]. Since the G-$R0^\circ$ layer sits on a buffer layer, also known as zeroth-layer graphene (ZLG), which is rotated $30^\circ$ with respect to the SiC substrate and still covalently bonded to it, decoupling the ZLG-$R30^\circ$ from the substrate can lead to high-quality twisted bilayer graphene (tBLG). Here we report the decoupling of ZLG-$R30^\circ$ by increasing the temperature during annealing in a borazine atmosphere. While this converts ZLG-$R30^\circ$ to G-$R30^\circ$ and thus produces tBLG, the growth process at elevated temperature is no longer self-limiting, so that the surface is covered by a patchwork of graphene multilayers of different thicknesses. We find a 20% coverage of tBLG on ZLG, while on the rest of the surface tBLG sits on one or more additional graphene layers. In order to achieve complete coverage with tBLG only, alternative ways of decoupling the ZLG, e.g., by intercalation with suitable atoms, may be advantageous.