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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排列成有序固体的这些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，那么固体就会显示出由于量子点之间相互作用而产生的新的光学和电子性质。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，通过用桥将量子点连接起来，或者用另一种材料填充量子点之间的空间，可以改变电子耦合。本研究旨在制备更有序的量子点超晶格，以探索材料的性质，并将其应用于太阳能电池、光电探测器和热电等器件。然而，人们很难调查看不到的结构。为了克服这一障碍，将开发使用近原子直接空间成像的高分辨率扫描透射式电子断层扫描。这种新的高分辨率层析成像数据将提供足够的细节来提供样品制备和所产生的超晶格有序之间的反馈，从而使得能够制备具有更大的超晶格磁区、更均匀分布的桥和更少的缺陷的更完美的样品。新的高分辨率数据还将使新的理论方法能够对固体中量子点之间的相互作用进行建模，以便超晶格有序的增加可以与光学和电子性质的特定变化联系在一起。长期目标是从足够完美的量子点开发固体，将电荷迁移率提高约十倍。这项研究将通过在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关于将在互联网上发布的材料的非技术性教育视频来与公众分享。对缺乏服务的社区的推广和教育将提供动手STEM培训。在超晶格中组织的胶体量子点(QD)在中尺度尺度上展示了集体电子和激子行为。关于微小的空间无序、表面化学缺陷和外延缺陷如何影响这种集体行为，或者如何制造更完美的超晶格结构的细节还不清楚。这个项目将使用分辨率为4-5ä的断层成像，超过1000个量子点来测量真实空间中这些小程度的结构无序。这项研究的重点是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体积。这些对图像质量的改进将使所有量子点、颈部和缺陷的近原子映射成为可能，推动在制造、结构控制和对电子结构/性质关系的理解方面的改进。近原子分辨率成像的反馈将使改进的制造成为可能，目标是100%的颈部连通性和均匀性，超晶格晶粒尺寸至少为10微米，电荷迁移率接近50cm2 V-1 S-1。改进的样品质量和高分辨率的3D真实空间成像将促进理论方法的发展，这些方法可以研究跳跃与电荷通过非定域“迷你带”的传输，并将通过变温霍尔效应测量进行验证。提出的层析成像突破了分辨率/体积的极限，实现了大尺度样品的高空间分辨率重建。预期的结果是多个超高分辨率断层图像，告知结构形成机制，改进的制造，质量传输，以形成QD-QD颈部，以及空间分辨率，以提供基于数据的现实电子建模。研究目标是多管齐下的，重点是可应用于其他量子点超晶格的制备设计规则，改进的扫描透射式电子层析技术以提高层析图像的空间分辨率和数据解释，以及使用真实空间数据对离域输运进行中尺度模拟。通过将这些方法结合在一起，该项目将纳米级结构、中级有序和大宗材料属性联系起来。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。