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，可以通过更改点的大小，形状或组成来改变其性能。这项研究是关于一旦将量子点组织成有序的固体（称为超晶格），这些量子点之间已排列为有序固体的这些量子点之间的相互作用，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性能。通过更改量子点之间的耦合来控制量子点超晶格的性能。通过控制颗粒之间的距离，将量子点与桥梁连接或通过用另一种材料在点之间的空间填充空间来改变电子耦合。这项研究旨在制造更多有序的量子点超晶格，以探索在太阳能电池，光电探测器和热电学等设备中利用的材料特性。但是，很难研究一个看不到的结构。为了克服这一障碍，将开发使用高分辨率扫描传输电子断层扫描与接近原子直接空间成像的使用。这种新的高分辨率层析成像数据将提供足够的详细信息，以提供样品制造和产生的超晶格顺序之间的反馈，以使具有更大的超级晶格域，更均匀分布的桥梁和较少缺陷的更完美的样品制造。新的高分辨率数据还将实现新的理论方法，以模拟固体中量子点之间的相互作用，以使超晶格顺序的增加可以与光学和电子性质的特定变化相关联。长期目标是从量子点开发固体，这些量子点足够完美，可以将电荷移动性提高约十倍。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层析成像数据并创建有关要在互联网上发布的材料的非技术教育视频，与公众共享。向服务不足的社区进行外展和教育将提供动手的STEM培训。在超级局部组织中组织的colloidal量子点（QD）已表现出整个中尺度维度的集体电子和令人兴奋的行为。尚不了解小度的空间疾病，表面化学缺陷和外延缺陷的细节会影响这种集体行为或如何制造更完美的超级晶格结构。该项目将使用以超过1000 QD的分辨率分辨率的层析成像成像来测量实际空间中这些小度的结构障碍。这项研究非常重视改进成像技术，以实现更高的分辨率并改善重建技术以增加图像量。这些对图像质量的改进将使所有QD，颈部和缺陷的原子图接近原子图，推动制造，结构控制以及对电子结构/特性关系的理解的改善。近原子分辨率成像的反馈将使颈部连接性和均匀性的目标能够改善制造，超级晶粒尺寸至少为10 µm，并且电荷迁移率接近50 CM2 V-1 S-1。改进的样品质量和高分辨率3D真实空间成像将有助于通过分离式“迷你频段”研究跳跃与电荷传输的理论方法，并将通过可变温度的霍尔效应测量值进行验证。提出的层析成像推动了分辨率/体积的限制，从而实现了具有高空间分辨率的大型中尺度样品的重建。预期的结果是多个超高分辨率的断层图，可为结构形成机理提供信息，改善制造，形成QD-QD颈部的质量传输以及空间分辨率，以根据数据为现实的电子建模提供信息。该研究目标是多渠道的，专注于制造设计规则，可以应用于其他QD超级局限器，改进的扫描传输电子断层扫描技术，以增强使用真实空间数据的分离式空间分辨率和数据解释以及对分离式传输的中尺度建模。通过结合这些方法，该项目在纳米级结构，中尺度秩序和批量材料属性之间建立联系。该奖项反映了NSF的法定任务，并使用基金会的知识分子优点和更广泛的影响审查标准，通过评估被认为是珍贵的支持。