Collaborative Research: Quantum Transport in Self-Assembled Hybrid Superlattices

当两个半导体以周期性结构结合在一起时，就会出现新的现象。这种半导体超晶格具有在大块半导体晶体中没有观察到的性质。它们的独特性质导致了新型器件的出现，如可调谐滤光器、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，需要超高真空和一层层细致的组装。PI的目标是发现一种基于混合钙钛矿的新型超晶格，这种材料既有有机成分，也有无机成分。杂化钙钛矿可以进行溶液处理，允许自发组装成层状纳米结构。它们的化学多样性可以极大地扩展具有不同性质的材料的范围，从而为超晶格研究带来革命性的变化。这项研究将使未来的超晶格器件成为可扩展和经济高效的。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和先进电子技术应用非常重要的量子异质结构。到目前为止，超晶格的成分仅限于无机半导体，如砷化镓和铝砷镓。这个项目将研究一类基于Ruddlesden-Popper卤化物钙钛矿的新型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，以加快材料发现。首先，我们将使用主密度泛函理论(DFT)计算来预测材料的结构，并将紧束缚模型与DFT计算相结合来模拟材料的光学和电学性质。超晶格结构将通过溶液处理和自组装来制备，允许通过改变成分来轻松地调节电子结构。使用半导体有机配体的设计策略将为带状工程创造新的可能性。电光测量将用于识别电子迷你频带等半导体超晶格的特征。互补的电学特性将被用来寻找量子输运的证据，利用光激发产生电荷载流子，而不会因为掺杂而产生意想不到的影响。该项目将阐明2D钙钛矿超晶格的性质，区分它们与传统无机超晶格的行为，并确定它们的光学和电学特性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智力优势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.