Near atomistic tomographic imaging of PbX quantum-dot superlattices for improved electronic and structural order

PbX 量子点超晶格的近原子断层扫描成像可改善电子和结构秩序

基本信息

批准号：
2005210
负责人：
Adam Moule
金额：
$ 60.38万
依托单位：
University of California-Davis
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2020
资助国家：
美国
起止时间：
2020-07-01 至 2024-06-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2005210&HistoricalAwards=false
关键词：
Near atomistic tomographic imaging PbX

项目摘要

Quantum dots are very small particles whose properties can be changed by changing the size, shape, or composition of the dot. This research is about understanding the interactions between these quantum dots that have been arranged into ordered solids Once the quantum dots are organized into ordered solids, called a super-lattice, then the solids exhibit new optical and electronic properties that arise from the interaction between the quantum dots. The properties of the quantum dot super-lattices are controllable by changing the coupling between the quantum dots. The electronic coupling is changed by controlling the distance between particles, by connecting the quantum dots with bridges, or by filling in the spaces between the dots with another material. This research seeks to fabricate more ordered quantum dot super-lattices to explore materials properties with utilization in devices like solar cells, photodetectors, and thermoelectrics. However, it is hard to investigate structures that one cannot see. To overcome this roadblock, the use of high-resolution scanning transmission electron tomography with near-atomic direct-space imaging will be developed. This new high-resolution tomographic data will provide sufficient detail to provide feedback between sample fabrication and resulting superlattice order to enable the fabrication of more perfect samples with larger super-lattice domains, more evenly distributed bridges, and fewer defects. The new high-resolution data will also enable new theoretical approaches to model the interaction between quantum dots in the solid so that increases in super-lattice order can be tied to specific changes in the optical and electronic properties. The long-term goal is to develop solids from quantum dots that are perfect enough to increase the charge mobility by about ten times. This research will be shared with the public by publishing the scanning transmission electron tomography data on a publicly downloadable forum and creating non-technical educational videos about the materials to be published on the internet. Outreach and education to underserved communities will provide hands-on STEM training.Colloidal quantum-dots (QDs), organized in a super-lattice, have demonstrated collective electronic and excitonic behavior across mesoscale dimensions. The specifics of how small degrees of spatial disorder, surface chemical defects, and epitaxial defects affect this collective behavior or how to fabricate more perfect super-lattice structures are not understood. This project will use tomographic imaging with a resolution of 4-5 Å over 1000s of QDs to measure these small degrees of structural disorder in real space. This research has a strong emphasis on improving the imaging technique to enable higher resolution and to improve the reconstruction technique to increase the image volume. These improvements to the image quality will enable near atomic mapping of all QDs, necks, and defects, driving improvement in fabrication, structural control, and understanding of electronic structure/property relationships. The feedback of near atomic resolution imaging will enable improved fabrication with the goals of 100% neck connectivity and uniformity with super-lattice grain sizes of at least 10 µm and charge mobility approaching 50 cm2 V-1 s-1. The improved sample quality and high-resolution 3D real-space imaging will facilitate theoretical approaches that can study hopping vs. charge transport through delocalized “mini-bands” and will be validated by variable-temperature Hall-effect measurements. The proposed tomography pushes the limits of resolution/volume achieving reconstructions of large mesoscale samples with high spatial resolution. The expected outcome is multiple ultra-high-resolution tomograms that inform the structure formation mechanism, improved fabrication, mass transport to form QD-QD necks, and spatial resolution to inform realistic electronic modeling based on data. The research goals are multi-pronged with focus on fabrication design rules that can be applied to other QD super-lattices, improved scanning transmission electron tomography techniques to enhance tomogram spatial resolution and data interpretation, and mesoscale modeling of delocalized transport using real spatial data. By combining these approaches this project connects between nanoscale structure, mesoscale order, and bulk materials properties.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.

量子点是非常小的粒子，可以通过改变点的大小、形状或成分来改变其特性。这项研究旨在了解这些排列成有序固体的量子点之间的相互作用。固体，称为超晶格，然后固体表现出由量子点之间的相互作用产生的新的光学和电子特性。量子点超晶格的特性可以通过改变量子之间的耦合来控制。通过控制粒子之间的距离、用桥连接量子点或用另一种材料填充点之间的空间来改变电子耦合。这项研究旨在制造更有序的量子点超晶格来探索材料。然而，为了克服这一障碍，需要使用近原子直接空间的高分辨率扫描透射电子断层扫描。这种新的高分辨率断层扫描数据将提供足够的细节，以在样品制造和最终的超晶格顺序之间提供反馈，从而能够制造出具有更大超晶格域、更均匀分布的桥和更少缺陷的更完美的样品。新的高分辨率数据还将启用新的理论方法来模拟固体中量子点之间的相互作用，从而使超晶格有序度的增加可以与光学和电子特性的特定变化联系起来。发展该研究将通过在可公开下载的论坛上发布扫描透射电子断层扫描数据并制作有关材料的非技术教育视频来与公众分享。将在互联网上发布。对服务不足的社区的宣传和教育将提供实践 STEM 培训。以超晶格组织的胶体量子点 (QD) 已经展示了跨中尺度的集体电子和激子行为。目前尚不清楚小程度的空间无序、表面化学缺陷和外延缺陷如何影响这种集体行为或如何制造更完美的超晶格结构，该项目将使用分辨率为 4-5 的断层扫描成像。超过 1000 个量子点来测量真实空间中这些小程度的结构紊乱。这项研究重点关注改进成像技术以实现更高的分辨率，并改进重建技术以增加图像质量。将要实现所有量子点、颈部和缺陷的近原子映射，推动制造、结构控制和对电子结构/性质关系的理解的改进。近原子分辨率成像的反馈将能够改进制造，以实现 100% 颈部连接和超晶格晶粒尺寸至少为 10 µm 且电荷迁移率接近 50 cm2 V-1 s-1 的均匀性，改进的样品质量和高分辨率 3D 实空间成像将有助于理论方法。可以通过离域“迷你带”研究跳跃与电荷传输，并将通过可变温度霍尔效应测量进行验证，突破了分辨率/体积的限制，实现了具有高空间分辨率的大型介观样品的重建。结果是多个超高分辨率断层图，可提供结构形成机制、改进制造、形成 QD-QD 颈部的质量传输，以及提供基于数据的实际电子建模的空间分辨率。多管齐下，重点关注可应用于其他量子点超晶格的制造设计规则，改进的扫描透射电子断层扫描技术以增强断层扫描空间分辨率和数据解释，以及使用真实空间数据进行离域传输的介观建模。该项目将纳米级结构、介观有序和散装材料特性联系起来。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。