Collaborative Research: Quantum Transport in Self-Assembled Hybrid Superlattices

当两个半导体在一个周期性结构中结合在一起时，就会出现新的现象。这种半导体超晶格具有在体半导体晶体中没有观察到的性质。它们独特的性质导致了新的器件，如可调谐光学滤波器，红外光电探测器和量子级联激光器。超晶格的制造成本很高，需要超真空和细致的逐层组装。PI旨在发现一种基于混合钙钛矿的新型超晶格，这种材料具有有机和无机成分。混合钙钛矿可以被溶液处理，允许自发组装成层状纳米结构。它们的化学多样性可以彻底改变超晶格研究，使其具有各种性质的材料范围大大扩展。这项研究将使未来的超晶格器件具有可扩展性和成本效益。该项目还将为本科生和研究生提供跨学科培训，为他们提供STEM和工业职业所需的批判性思维和解决问题的技能。半导体超晶格是对凝聚态物理重要的量子异质结构，在先进的电子技术中具有应用。到目前为止，超晶格的成分仅限于无机半导体，如GaAs和AlGaAs。该项目将研究基于Ruddlesden-Popper卤化物钙钛矿的一类新的半导体超晶格中的量子输运。该项目将以迭代的方式进行理论和实验研究，以加速材料发现。第一原理密度泛函理论（DFT）计算将用于预测材料结构，并将通过结合紧束缚模型与DFT计算来模拟光学和电子性质。超晶格结构将通过溶液处理和自组装来制备，从而允许通过改变成分来容易地调整电子结构。设计策略，使用半导体有机配体，将创造新的能带工程的可能性。电光测量将用于识别半导体超晶格的特征，如电子能带。互补的电特性将被用来寻找量子传输的证据，使用光激发产生电荷载流子，而不会产生意外的影响掺杂。该项目将阐明二维钙钛矿超晶格的性质，将其行为与传统无机超晶格区分开来，并确定其光学和电子性质是否可以以可控的方式定制。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

New phenomena emerge when two semiconductors are brought together in a periodic structure. Such semiconducting superlattices have properties not observed in bulk semiconductor crystals. Their unique properties have led to novel devices such as tunable optical filters, infrared photodetectors, and quantum cascade lasers. Superlattices are expensive to make, requiring ultrahigh vacuum and meticulous layer by layer assembly. The PIs aim to discover a new type of superlattice based on hybrid perovskites, materials with both organic and inorganic components. Hybrid perovskites can be solution processed, allowing for spontaneous assembly into layered nanostructures. Their chemical diversity can revolutionize superlattice research with a vastly expanded range of materials with varied properties. This research will enable future superlattice devices that are scalable and cost-effective. This project will also provide interdisciplinary training to undergraduate and graduate students, providing them with critical-thinking and problem-solving skills needed for CAREERs in STEM and industry.Semiconducting superlattices are quantum heterostructures important to condensed matter physics and with applications in advanced electronic technologies. The constituents of the superlattices to date have been limited to inorganic semiconductors, such as GaAs and AlGaAs. This project will investigate quantum transport in a new class of semiconducting superlattices based on Ruddlesden-Popper halide perovskites. The project will employ theoretical and experimental studies in an iterative manner so as to accelerate materials discovery. First principle density functional theory (DFT) calculations will be used to predict materials structures and the optical and electronic properties will be modeled by combining tight-binding models with the DFT calculations. Superlattice structures will be prepared by solution processing and self-assembly, allowing for facile tuning of the electronic structure by varying constituents. The design strategy, using semiconducting organic ligands, will create new possibilities for band engineering. Electrooptical measurements will be used to identify signatures of semiconducting superlattices such as electronic minibands. Complementary electrical characterization will be used to search for evidence of quantum transport, using optical excitation to generate charge carriers without unintended effects arising from doping. The project will elucidate the properties of 2D perovskite superlattices, differentiate their behaviors from conventional inorganic superlattices, and determine if their optical and electronic properties can be tailored in a controllable manner.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.