Collaborative Research: Combined transport and scanning probe study of twisted van der Waals devices

许多半导体器件依赖于创建由多个层组成的异质结构以实现其期望的功能。 传统的半导体异质结构由于不同层之间的晶格匹配的要求而在可利用的材料的选择方面受到限制。 然而，原子级薄的材料有能力克服这一限制，通过创建货车德瓦尔斯异质结构实现的一层一层堆叠的方法。 这将允许在这些异质结构中创建更宽范围的电子特性。 此外，它们具有额外的自由度，即不同层之间的扭曲角，这在层之间产生长波长莫尔图案。 这种莫尔图案调制电子特性，并可以产生相关状态，如超导性或磁性。 在这个项目中，我们将使用MX2形式的半导体过渡金属二硫族化物，其中M是过渡金属，X是硫族元素，以创建新的布尔逻辑器件，其中层间的扭曲角控制电子特性。 该项目将开发新的制造技术，表征新的电子特性，然后基于这些新开发的异质结构实现逻辑器件。 拟议的计划将通过促进量子材料和器件跨学科领域的发展，在亚利桑那大学和德克萨斯大学奥斯汀分校创造新的教育和研究机会。特别是，拟议的研究符合NSF量子飞跃的大理念：通过开发有潜力实现新量子技术的材料系统和设备来领导下一次量子革命。 这项研究计划将着重培养研究生和本科生，从而为他们的工业或学术生涯做好准备。这项合作计划将通过异质结构设计、逐层制造、扫描探针显微镜和电输运测量来设计和表征具有平坦能带的货车德瓦尔斯异质结构器件。 该项目将集中在二维半导体过渡金属二硫属化物的同质双层异质结构与控制层之间的扭曲角。 由于相邻层之间的扭转角，长波长莫尔图案形成，其修改异质结构的电子性质，并且可以导致平坦的能量-动量色散。 这些平带具有大的态密度和小的带宽，使得相互作用效应将主导它们的动能。 在这种情况下，电子效应变得高度相关，我们将利用这些特性来创建新的设备。 我们特别要实现以下三个目标：（1）门可调TMD双层和三层异质结构的开发和表征，（2）通过静电门控、扭曲和应变控制产生新的相关态，（3）约瑟夫森结场的实现该奖项反映了NSF的法定使命，并已被认为是值得通过使用评估的支持，基金会的学术价值和更广泛的影响评审标准。

Many semiconductor devices rely on creating heterostructures consisting of multiple layers to enable their desired functionality. Traditional semiconductor heterostructures are limited in the choice of materials that can be utilized because of requirements of lattice matching between the different layers. However, atomically thin materials have the ability to overcome this limitation through the creation of van der Waals heterostructures realized in a layer-by-layer stacking approach. This will allow a much wider range of electronic properties to be created in these heterostructures. Furthermore, they have an additional degree of freedom which is the twist angle between different layers, which gives rise to a long wavelength moiré pattern between the layers. This moiré pattern modulates the electronic properties, and can give rise to correlated states such as superconductivity or magnetism. In this project, we will use semiconducting transitional metal dichalcogenides of the form MX2 where M is a transition metal, and X is a chalcogen to create novel Boolean logic devices where the twist angle between layers controls the electronic properties. The proposed project will develop new fabrication techniques, characterize the novel electronic properties, and then implement logic devices based on these newly developed heterostructures. The proposed program will create new educational and research opportunities at University of Arizona and The University of Texas at Austin by fostering the growth of the interdisciplinary area of quantum materials and devices. In particular, the proposed research aligns with the NSF Big Idea of Quantum Leap: Leading the Next Quantum Revolution by developing material systems and devices that have the potential to enable new quantum technologies. This proposed research prog-ram will strongly emphasize the training of graduate and undergraduate students, thus preparing them for industrial or academic careers.This collaborative proposal will engineer and characterize van der Waals heterostructure devices with flat bands through heterostructure design, layer-by-layer fabrication, scanning probe microscopy, and electrical transport measurements. The project will be focused on homobilayer heterostructures of two-dimensional semiconducting transition metal dichalcogenides with controlled twist angle between the layers. Due to the twist angle between adjacent layers, a long wavelength moiré pattern develops which modifies the electronic properties of the heterostructure and can lead to an energy-momentum dispersion that is flat. These flat bands have a large density of states and small bandwidth such that interaction effects will dominate over their kinetic energy. In this regime, the electronic effects become highly correlated and we will exploit these properties for the creation of novel devices. In particular, we will accomplish the following three aims: (1) Development and characterization of gate tunable TMD homobilayer and trilayer heterostructures, (2) Creation of novel correlated states through electrostatic gating, twist and strain control, and (3) Realization of Josephson junction field-effect transistors for Boolean logic applications.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.