MAX IV Laboratory, Lund University, Fotongatan 2, 22484 Lund, Sweden.
Department of Microtechnology and Nanoscience, Chalmers University of Technology, 412 96, Gothenburg, Sweden.
Phys Rev Lett. 2023 Feb 17;130(7):076203. doi: 10.1103/PhysRevLett.130.076203.
The long theorized two-dimensional allotrope of SiC has remained elusive amid the exploration of graphenelike honeycomb structured monolayers. It is anticipated to possess a large direct band gap (2.5 eV), ambient stability, and chemical versatility. While sp^{2} bonding between silicon and carbon is energetically favorable, only disordered nanoflakes have been reported to date. Here we demonstrate large-area, bottom-up synthesis of monocrystalline, epitaxial monolayer honeycomb SiC atop ultrathin transition metal carbide films on SiC substrates. We find the 2D phase of SiC to be almost planar and stable at high temperatures, up to 1200 °C in vacuum. Interactions between the 2D-SiC and the transition metal carbide surface result in a Dirac-like feature in the electronic band structure, which in the case of a TaC substrate is strongly spin-split. Our findings represent the first step towards routine and tailored synthesis of 2D-SiC monolayers, and this novel heteroepitaxial system may find diverse applications ranging from photovoltaics to topological superconductivity.
碳化硅的二维理论同素异形体在探索类石墨烯蜂窝状单层结构的过程中一直难以捉摸。预计它具有大的直接带隙（2.5 eV）、环境稳定性和化学多功能性。虽然硅和碳之间的 sp^{2}键合在能量上是有利的，但迄今为止只报道了无序的纳米薄片。在这里，我们展示了在 SiC 衬底上的超薄过渡金属碳化物薄膜上，大面积自下而上合成单晶、外延单层蜂窝状碳化硅。我们发现 2D 相的碳化硅几乎是平面的，在高温下（真空下高达 1200°C）稳定。二维-SiC 和过渡金属碳化物表面之间的相互作用导致了电子能带结构中的类狄拉克特征，在 TaC 衬底的情况下，这种特征强烈地自旋分裂。我们的发现代表了 2D-SiC 单层常规和定制合成的第一步，这种新型的异质外延系统可能在从光伏到拓扑超导的各种应用中找到。
