Van der Waals Heteromaterials

非技术描述：层状材料由两维分子平面组成，这些分子平面堆叠在一起，仅靠微弱的力保持在一起。尽管层之间的相互作用很弱，但最近的研究表明，层之间的相互作用在控制这些材料的性能方面是至关重要的。在自然界中，层状化合物表现出相同的层组成。在这个项目中，研究团队将各种具有原子层精度的层状材料结合在一起，从而创造出具有新颖性能的人工层状材料。具体地说，该团队正在获得不同层状材料之间的界面如何控制材料属性的见解，这对在纳米尺度上设计材料具有深远的影响。对层间相互作用的更好理解使发现具有超导或太阳能收集等多种应用的新材料成为可能。该计划倡导增加STEM研究中的少数族裔学生，并将其纳入允许研究生在欧洲的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，范德华材料中的量子限制和层间杂化强烈地改变了单层材料的性质。该研究小组的目标是了解这种弱的层间相互作用如何改变人造范德华异质结构的性质，并探索如何利用这些修改来设计具有理想性能的材料。在本项目中，通过在范德华衬底上直接生长层状材料来合成范德华异质结构。用角度分辨光电子能谱和扫描隧道显微镜/光谱表征了由于层间相互作用而引起的电子性质的变化。扫描探头技术还允许对人工生长的纳米结构和横向界面进行表征。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转变温度的调节。在半导体材料中，正在研究作为不同材料的层和/或界面的函数的带隙调谐。最后，通过将生长单层的能力与一种新的纳米探针在超高真空条件下的输运测量相结合，探索了通过分子吸附、电荷转移掺杂或场效应来改变单层电子性质。

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.