Interlayer excitons in advanced, CVD-based van der Waals heterostructures with controlled moiré wavelength

具有受控莫尔波长的先进 CVD 范德华异质结构中的层间激子

• 批准号: 443361515
• 负责人: Professor Dr. Tobias Korn
• 金额: --
• 依托单位: Institut für Experimentelle und Angewandte Physik
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/443361515?language=en
• 关键词: Interlayer; excitons; advanced; CVD; based

We propose to fabricate advanced transition metal dichalcogenide (TMDC) heterostructures (HS) with controlled moiré wavelength using TMDC monolayers (MLs) grown by chemical vapor Deposition CVD). This process yields large (>100 micrometer) ML flakes with well-defined triangular shape, directly locked to crystallographic orientation. It was recently demonstrated that removing them from the growth substrate and encapsulating them in hexagonal boron Nitride (hBN) yields low spectral linewidths comparable to exfoliated MLs. Therefore, these samples present a novel, abundant building block for HS. Additionally, we can control twist angles with great accuracy by simply measuring the orientation of the long, well-defined edges, instead of relying on the less precise and laborious second-harmonic-generation microscopy. We will study interlayer excitons (ILEs) in these advanced HS using various low-temperature spectroscopy techniques, including micro-photoluminescence, Faraday rotation and Kerr microscopy, to systematically determine the influence of the reciprocal space (mis-)alignment and the moiré-induced superlattice potential on ILE energy, photoluminescence lifetimes, valley polarization dynamics and diffusion. Since the abundance of CVD MLs removes an important bottleneck for fabrication, we also plan on building HS with higher complexity by integrating ferromagnetic layers, which will allow us to break valley degeneracy by proximity effects. In parallel, we will endeavor to further optimize the CVD growth techniques for direct, single-process growth of TMDC HS. In direct CVD growth, we can expect an epitaxial alignment of the two TMDCs, generating structures that are fundamentally different from any HS we can fabricate by deterministic stacking: directly grown epitaxial TMDC HS are free of moiré-related effects and thus provide an important reference. Additionally, we will introduce novel substrates for CVD growth, such as epitaxially grown hBN.

我们建议使用通过化学气相沉积CVD生长的TMDC单层（ML）来制造具有受控莫尔波长的先进过渡金属二硫属化物（TMDC）异质结构（HS）。该过程产生具有明确三角形形状的大（>100微米）ML薄片，直接锁定晶体取向。最近的研究表明，将它们从生长基底上移除并将它们封装在六方氮化硼 (hBN) 中，可以产生与剥离的 ML 相当的低光谱线宽。 因此，这些样品为 HS 提供了一种新颖、丰富的构建模块。此外，我们可以通过简单地测量明确的长边缘的方向来非常精确地控制扭转角度，而不是依赖不太精确且费力的二次谐波产生显微镜。我们将使用各种低温光谱技术（包括微光致发光、法拉第旋转和克尔显微镜）研究这些先进HS中的层间激子（ILE），以系统地确定倒易空间（错误）对准和莫尔引起的超晶格势对ILE能量、光致发光寿命、谷偏振动力学和扩散的影响。由于丰富的 CVD ML 消除了制造的一个重要瓶颈，我们还计划通过集成铁磁层来构建具有更高复杂性的 HS，这将使我们能够通过邻近效应打破谷简并性。 与此同时，我们将努力进一步优化 CVD 生长技术，以实现 TMDC HS 的直接、单工艺生长。在直接 CVD 生长中，我们可以预期两个 TMDC 会外延排列，产生与我们通过确定性堆叠制造的任何 HS 根本不同的结构：直接生长的外延 TMDC HS 没有莫尔相关效应，因此提供了重要的参考。此外，我们还将推出用于 CVD 生长的新型基板，例如外延生长的六方氮化硼。