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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，其性质可以通过改变点的大小、形状或组成来改变。这项研究是关于理解这些排列成有序固体的量子点之间的相互作用，一旦量子点被组织成有序固体，称为超晶格，那么固体就会表现出新的光学和电子特性，这些特性是由量子点之间的相互作用产生的。通过改变量子点之间的耦合，可以控制量子点超晶格的性质。通过控制粒子之间的距离，用桥连接量子点，或者用另一种材料填充量子点之间的空间来改变电子耦合。本研究旨在制造更有序的量子点超晶格，以探索材料在太阳能电池、光电探测器和热电器件中的应用。然而，很难研究人们看不见的结构。为了克服这一障碍，将开发高分辨率扫描透射电子断层扫描与近原子直接空间成像的使用。这种新的高分辨率层析数据将提供足够的细节，在样品制造和产生的超晶格顺序之间提供反馈，从而使制造更完美的样品具有更大的超晶格域，更均匀分布的桥和更少的缺陷。新的高分辨率数据还将使新的理论方法能够模拟固体中量子点之间的相互作用，因此超晶格顺序的增加可以与光学和电子特性的特定变化联系起来。长期目标是从量子点中开发出足够完美的固体，使电荷迁移率提高约十倍。这项研究将通过在一个可公开下载的论坛上发布扫描传输电子断层扫描数据，并制作有关将在互联网上发布的材料的非技术教育视频，与公众分享。向服务不足的社区提供外展和教育将提供动手干培训。在超晶格中组织的胶体量子点（QDs）在中尺度尺度上表现出集体电子和激子行为。至于小程度的空间无序、表面化学缺陷和外延缺陷如何影响这种集体行为，以及如何制造更完美的超晶格结构的细节，目前还不清楚。该项目将使用分辨率为4-5 Å / 1000s量子点的层析成像来测量真实空间中这些小程度的结构紊乱。本研究的重点是改进成像技术以获得更高的分辨率，改进重建技术以增加图像体积。这些图像质量的改进将使所有量子点、瓶颈和缺陷的近原子映射成为可能，从而推动制造、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有助于改进制造，实现100%的颈部连通性和均匀性，超晶格晶粒尺寸至少为10 μ m，电荷迁移率接近50 cm2 V-1 s-1。改进的样品质量和高分辨率的三维实时空间成像将促进通过离域“迷你带”研究跳变与电荷输运的理论方法，并将通过变温霍尔效应测量进行验证。所提出的断层扫描突破了分辨率/体积的限制，实现了高空间分辨率的大中尺度样品的重建。预期的结果是多种超高分辨率层析成像，可以了解结构形成机制，改进制造，质量传输以形成QD-QD颈部，以及基于数据的空间分辨率，为现实的电子建模提供信息。研究目标是多管齐下的，重点是可以应用于其他量子点超晶格的制造设计规则，改进扫描透射电子断层扫描技术以提高层析成像的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中尺度建模。通过结合这些方法，本项目将纳米尺度结构、中观尺度秩序和块状材料特性联系起来。该奖项反映了美国国家科学基金会的法定使命，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。