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

该HBCU-UP奖项支持理论和计算研究，一方面模拟和预测新型量子点，另一方面在物理系内开发多学科计算物理程序。量子点被称为人造原子或分子，这取决于它们的大小和组成。它们的尺寸范围从1 - 100纳米的直径和原子的数量从数百到数万。虽然原子的组成和性质是由自然界预先确定的，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。创造新型纳米结构的机会数不胜数，这使得量子点成为研究基础物理和技术应用的丰富系统。该项目旨在融合两种不同的量子点，即等离子体量子点和稀磁量子点。等离子体材料基于被称为等离子体的固体中的电子的集体运动。这些材料的研究主要是在宏观尺度上用经典电磁理论进行的。十年前，在量子点表面发现了一种新的等离子体特性，称为局域表面等离子体。现有的经典物理学方法必须被量子力学所取代，以理解涌现现象。但是，为量子点这样的有限系统开发新的理论需要计算方法，因为有限性打破了通常用来解决周期系统问题的平移对称性。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。这些量子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，该项目将研究等离子体材料在掺杂少量磁性离子时的铁磁性。这些材料本身就对未来量子计算机和自旋电子学的应用感兴趣。最终，这两条轨道将结合起来，看看多功能新型材料的可能性。该奖项将支持建立一个计算物理程序。PI将与计算物理学家和计算机科学家合作，在德克萨斯州高级计算中心（TACC）提供类似项目的课程。 TACC的资源将用于培训高性能计算平台的学生。在他们的高年级，学生将研究问题的工作。课程和培训预计将为学生在高科技行业的工作做好准备，或继续他们的研究和计算经验进入研究生院。此外，该奖项将支持一名研究生。PI将参与社区大学和高中的推广计划，以增加计算物理课程的学生人数。技术摘要本提案旨在通过用磁性和非磁性掺杂剂共掺杂来设计多功能半导体氧化物量子点。该项目将有三个重点：1）半导体纳米等离子体氧化物：将利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）带间跃迁效应，ii）载流子的局部化，iii）配体和邻近效应，iv）小尺寸量子点的量子限制效应，和v）比由Drude-Lorentz模型很好地描述的贵金属纳米晶体的载流子更少的载流子。2）掺杂有TM的半导体氧化物量子点：由于合成中涉及大量的竞争参数，半导体氧化物中的铁磁性的演变通常是有争议的。将进行过渡金属掺杂的半导体氧化物量子点的电子和磁性结构的详细研究，该研究涵盖了掺入不同量的掺杂剂杂质、空位和晶体缺陷（如晶体）的宽参数空间。3）等离子体稀磁半导体氧化物量子点：在进行步骤1）和2）之后，将研究组合系统。 纳米等离子体激元氧化物将掺杂有稀量的过渡金属原子，并且稀释的磁性氧化物量子点掺杂有非磁性供体。将组合系统的电子和磁性结构与1）和2）的结果进行比较。这项研究将涉及一名研究生和介绍本科生的研究协议。在研究的同时，将启动一个计算物理轨道，将培养本科生在科学超级计算。计算物理学计划预计将增加物理专业的人数。PI还将参与社区大学和高中的外展计划。该奖项反映了NSF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。

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.