Atomically resolved phonon and photon spectroscopies of 2D material stackings

二维材料堆叠的原子分辨声子和光子光谱

• 批准号: 467613242
• 负责人: Professor Dr. Jörg Kröger
• 金额: --
• 依托单位: Fachgebiet Experimentalphysik I
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/467613242?language=en
• 关键词: Atomically; resolved; phonon; photon; spectroscopies

The project addresses double-layers of graphene and stackings of graphene and hexagonal boron nitride (h-BN) on metal surfaces – Ru(0001), Rh(111) and Pt(111). The first aim is the preparation of the bilayer structures in a surface science approach in order to ensure the presence of domains with different twist angles between the stacked two-dimensional materials. The rotation angle between the 2D lattices will be inferred from the analysis of the resulting moiré patterns by electron diffraction and scanning tunnelling microscopy. The second target consists in exploring electronic properties, phonon and photon excitations of these stacked hybrid materials with scanning tunnelling spectroscopy. The focus is on the potential dependence of the aforementioned properties on the twist angle. The planned approach allows the direct comparison of local phonon and photon excitations with the electronic structure. In addition, owing to the presence of twist angle domains on one and the same sample, the experiments will identify the dependence of the quantum properties on the twist angle without the necessity to change the sample. The unique opportunities of the scanning tunnelling microscope shall be used to explore the importance of Van Hove singularities for phonons in bilayer graphene. A possible energy reduction of specific phonon modes due to an enhanced electron-phonon correlation in terms of a Kohn anomaly will be scrutinized. There is a debate on the role of Van Hove singularities in the photon emission of bilayer graphene, where ooptical transitions between the singularities and strongly bound excitons induced by the singularitues compete with each other. The local photon emission from the tunnelling barrier depending on the moiré lattice site and on the twist angle shall elucidate the debate. Single defects in the h-BN lattice on graphene will be prepared using argon ion bombardment in order to study their optical properties as colour centers. To this end, spectroscopy of the local electroluminescence induced by the injected tunnelling current will be performed.

该项目涉及双层石墨烯以及金属表面--Ru(0001)、Rh(111)和Pt(111)上的石墨烯和六方氮化硼(h-BN)堆积。第一个目标是用表面科学的方法制备双层结构，以确保在堆叠的二维材料之间存在具有不同扭转角的磁区。2D晶格之间的旋转角将通过电子衍射和扫描隧道显微镜对所产生的莫尔图案的分析来推断。第二个目标是用扫描隧道光谱研究这些堆积杂化材料的电子性质、声子和光子激发。重点放在上述性质与扭转角度的潜在依赖关系上。计划中的方法允许直接将局域声子和光子激发与电子结构进行比较。此外，由于在同一样品上存在扭转角域，实验将在不改变样品的情况下确定量子性质与扭转角度的依赖关系。扫描隧道显微镜的独特机会将被用来探索双层石墨烯中声子的范霍夫奇点的重要性。我们将仔细研究由于Kohn反常而增强的电子-声子关联可能导致的特定声子模的能量降低。关于Van Hove奇点在双层石墨烯光子发射中的作用一直存在争议，奇点和由奇点引起的强束缚激子之间的光学跃迁相互竞争。隧道势垒的局域光子发射取决于莫尔晶格位置和扭转角度，这将阐明这一争论。利用Ar离子轰击制备石墨烯上h-BN晶格中的单缺陷，以研究其作为色心的光学性质。为此，将执行由注入的隧道电流诱导的局部电致发光的光谱。