Van der Waals Heteromaterials

非技术描述：层状材料由二维分子平面组成，它们彼此堆叠在一起，仅靠弱力就能结合在一起。虽然层之间的相互作用很弱，但最近的研究表明，它们在控制这些材料的性能方面是至关重要的。在自然界中，层状化合物具有相同的层组成。在这个项目中，研究团队将不同的层状材料与原子层精度相结合，从而创造出具有新颖性能的人工层状材料。具体来说，该团队正在深入了解不同层状材料之间的界面如何控制材料性能，这对纳米级材料的设计具有深远的意义。更好地理解层间相互作用可以发现具有多种应用的新材料，如超导或太阳能收集。该项目提倡增加少数族裔学生参与STEM研究，并将其纳入研究生在欧洲研究机构获得国际经验的活动中。技术描述：与块状材料相比，范德瓦尔斯材料中的量子约束和层间杂化强烈地改变了单层材料的性质。研究小组旨在了解这种弱层间相互作用如何改变人工范德华异质结构的性质，并探索如何利用这些改变来设计具有理想性能的材料。在这个项目中，范德华异质结构是通过在范德华衬底上直接生长层状材料来合成的。利用角度分辨光发射光谱和扫描隧道显微镜/光谱技术对层间相互作用引起的电子性质变化进行了表征。扫描探针技术也允许表征人工生长的纳米结构和横向界面。量子临界现象，如电荷密度波跃迁，预计将敏感地依赖于层间相互作用，因此正在研究金属材料中跃迁温度的调谐。在半导体材料中，带隙调谐作为层和/或不同材料界面的函数正在被研究。最后，在超高真空条件下，通过分子吸附、电荷转移掺杂或场效应，结合单层生长能力和新的纳米探针输运测量，探索了单层电子性能的改变。

Nontechnical Description: Layered materials consists of two-dimensional molecular-planes that are stacked on top of each other and held together by only weak forces. Although the interactions between layers are weak, it has been recently shown that they are critical in controlling the properties of these materials. In nature, layered compounds exhibit identical layer composition. In this project, the research team is combining diverse layered materials with atomic layer precision and thus creates artificially layered materials with novel properties. Specifically, the team is gaining insight how interfaces between dissimilar layered materials controls material properties and this has far reaching implications for designing materials at the nanoscale. Better understanding of interlayer interactions enables discovery of novel materials with applications as diverse as superconductivity or solar energy harvesting. The program advocates the increase of minority students in STEM research and is embedded in activities which allows graduate students to gain experience internationally at research facilities in Europe. Technical Description: Quantum confinement and interlayer hybridization in van der Waals materials strongly modify the properties of single layers compared to bulk materials. The research team aims to understand how such weak interlayer interactions modify the properties of artificial van der Waals heterostructures and explores how these modifications can be utilized for designing materials with desirable properties. In this project, van der Waals heterostructures are synthesized by direct growth of layered materials on van der Waals substrates. The variation of their electronic properties due to interlayer interactions are characterized by angle resolved photoemission spectroscopy and scanning tunneling microscopy/spectroscopy. Scanning probe techniques also allow the characterization of artificially grown nanostructures and lateral interfaces. Quantum critical phenomena, such as charge density wave transitions, are anticipated to be sensitively dependent on interlayer interactions and thus the tuning of transition temperatures is being studied in metallic materials. Band gap tuning as a function of layers and/or interfaces with dissimilar materials are being studied in semiconducting materials. Finally, modifications of single layer electronic properties by molecular adsorption, charge transfer doping, or field effect is explored by combining the capabilities of growing single layers with a new nanoprobe transport measurement under ultra-high vacuum conditions.