Excellence in Research: First Principles Defect Engineering of Plasmonic Diluted Magnetic Semiconducting Oxide Nanocrystals

非技术概述这一HBCU-UP奖一方面支持理论和计算研究，以模拟和预测新的量子点，另一方面支持在物理系内发展一个多学科的计算物理计划。根据量子点的大小和组成，量子点被称为人造原子或分子。它们的直径从1-100纳米不等，原子数量从数百个到数万个不等。虽然原子的组成和性质是由自然预先确定的，但人造原子或分子的性质可以通过改变它们的大小和组成来操纵。创造新的纳米结构有无数的机会，这使得量子点成为研究基础物理和技术应用的丰富系统。该项目寻求合并两种不同类型的量子点，即等离子体量子点和稀磁量子点。等离子体材料是基于电子在固体中的集体运动，这种固体被称为等离子体。直到最近，这些材料还主要是用经典的电磁学理论在宏观尺度上进行研究。十年前，人们在量子点表面发现了等离子体激元的一种新特性，即定域表面等离子体激元。为了理解浮现现象，必须用量子力学取代经典物理学的现有方法。但是，为像量子点这样的有限系统开发新的理论需要计算方法，因为有限打破了通常用来解决周期系统问题的平移对称。PI将应用量子力学和半经典计算技术来研究一系列等离子体量子点。这些点有望在光子学和光电子学中得到应用。在一个单独的轨道上，该项目将研究当掺入稀释量的磁性离子时，铁磁性开始时的等离子体材料。这些材料本身对应用于未来的量子计算机和自旋电子学是有意义的。最终，这两个轨道将被结合在一起，以看到多功能新颖材料的可能性。该奖项将支持建立一个计算物理项目。PI将与计算物理学家和计算机科学家合作，仿照德克萨斯州先进计算中心(TACC)的类似计划提供课程。TACC的资源将用于对学生进行高性能计算平台的培训。在大四期间，学生们将致力于研究问题。课程设置和培训预计将为学生在高科技行业的工作做好准备，或者继续他们的研究和计算经验进入研究生院。此外，该奖项还将资助一名研究生。PI将参与社区大学和高中的外展项目，以增加计算物理课程的学生人数。技术总结这项提案旨在通过在半导体氧化物量子点中混合磁性和非磁性掺杂剂来设计多功能半导体氧化物量子点。该项目将有三个推力：1)半导体纳米等离子氧化物：将采用密度泛函理论和动力学蒙特卡罗技术进行第一性原理计算，以开发新的物理模型，这些模型可以解决：i)带间跃迁的影响，ii)载流子的局域化，iii)配体和邻近效应，iv)小尺寸量子点的量子限制效应，以及v)比贵金属纳米晶体的载流子更少的载流子，由Drude-Lorentz模型很好地描述。2)掺杂TMS的半导体氧化物量子点：由于合成过程中涉及到大量的竞争性参数，因此半导体氧化物中铁磁性的演化通常是有争议的。详细研究过渡金属掺杂半导体氧化物量子点的电子和磁性结构，包括不同数量的掺杂杂质、空位和晶格缺陷。3)等离子体稀磁半导体氧化物量子点：在步骤1)和步骤2)之后，将对组合系统进行研究。纳米等离子体氧化物将被掺入稀释量的过渡金属原子和稀磁氧化物量子点与非磁性施主。将组合体系的电子结构和磁性结构与1)和2)的结果进行比较。这项研究将包括一名研究生和向本科生介绍研究方案。与这项研究同步进行的是，将启动一条计算物理轨道，培训本科生进行科学超级计算。计算物理项目预计将增加物理专业的数量。PI还将参与社区大学和高中的外展计划。这一奖项反映了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。

Non-technical SummaryThis HBCU-UP award supports theoretical and computational research to simulate and predict novel quantum dots on the one hand and to develop a multidisciplinary computational physics program within the Department of Physics on the other. Quantum dots have been termed artificial atoms or molecules depending on their size and composition. They range in size from 1 – 100 nm in diameter and in numbers of atoms from hundreds to tens of thousands. While the composition and properties of atoms are predetermined by nature, the properties of artificial atoms or molecules can be manipulated by varying their size and composition. Myriad opportunities exist to create novel nanostructures, and this makes quantum dots a rich system for investigating fundamental physics as well as for technological applications.The project seeks to merge two different kinds of quantum dots, namely plasmonic quantum dots and diluted magnetic quantum dots. Plasmonic materials are based on collective motions of electrons in solids known as plasmons. These materials had been studied mostly on the macroscopic scale with classical electromagnetism theory until recently. A new property of plasmons known as localized surface plasmons was discovered on the surface of quantum dots a decade ago. The existing approach of classical physics has to be replaced with quantum mechanics in order to understand the emergent phenomena. But developing a new theory for a finite system such as a quantum dot requires computational methodology, since the finiteness breaks the translational symmetry often invoked to solve problems for periodic systems. The PI will apply quantum-mechanical as well as semi-classical computational techniques to study a range of plasmonic quantum dots. These dots are expected to have application in photonics and optoelectronics. On a separate track, the project will investigate the plasmonic materials for the onset of ferromagnetism when doped with a dilute amount of magnetic ions. These materials are of interest in their own right for applications to prospective quantum computers and spintronics at large. Eventually, the two tracks will be combined to see the possibility of a multifunctional novel material. The award will support the establishment of a computational physics program. The PI will work with computational physicists and computer scientists to offer courses modelled after a similar program at the Texas Advanced Computing Center (TACC). TACC resources will be used to train the students on high-performance computing platforms. During their senior year, the students will work on research problems. The course offerings and training are expected to prepare the students for jobs in high tech industry or to continue their research and computational experience into graduate school. In addition, the award will support a graduate student. The PI will be involved in outreach programs to community colleges and high schools to increase the number of students in the computational physics program.Technical SummaryThis proposal aims to design multifunctional semiconducting oxide quantum dots by co-doping them with magnetic and non-magnetic dopants. The project will have three thrusts:1) Semiconducting nanoplasmonic oxides: First-principles calculations with density functional theory and the kinetic Monte Carlo technique will be performed to develop new physical models that could address i) the effect of band-to-band transitions, ii) localization of carriers, iii) ligand and proximal effects, iv) quantum confinement effects for small-sized quantum dots, and v) fewer carriers than those of noble metal nanocrystals that are well described by the Drude-Lorentz model.2) Semiconducting oxide quantum dots doped with TMs: The evolution of ferromagnetism in semiconducting oxides is controversial in general because of the large number of competing parameters involved in the synthesis. A detailed study of the electronic and magnetic structures of transition-metal-doped semiconducting oxide quantum dots throughout a wide parameter space which covers the incorporation of varying amounts of dopant impurities, vacancies, and crystalline defects such as interstitials will be conducted.3) Plasmonic diluted magnetic semiconducting oxide quantum dots: After steps 1) and 2) have been undertaken, the combined system will be studied. The nanoplasmonic oxides will be doped with dilute amounts of transition metal atoms and the diluted magnetic oxide quantum dots with non-magnetic donors. Electronic and magnetic structures of the combined system will be compared to results from 1) and 2). The research will involve a graduate student and introduction of undergraduates to research protocols. In tandem with the research, a computational physics track will be launched that will train undergraduate students in scientific supercomputing. The computational physics program is expected to increase the number of physics majors. The PI will be also involved in outreach programs to community colleges and high schools.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.