Placing spins in semiconductors

采用钙钛矿晶体结构的金属卤化物半导体的显著光学和电子性质使它们成为太阳能电池和发光器件（例如，LED）。然而，在这些应用中表现出色的钙钛矿是不稳定的。因此，具有优异的光学和电子特性以及高密度磁自旋的金属卤化物基本上仍然未知。 通过该项目，在材料研究部的固态和材料化学以及电子和光子材料项目的支持下，斯坦福大学的Hema Karunadasa教授和她的研究小组提出了在溶液中形成的新磁性半导体的设计和合成。这些材料主要由金属离子和卤化物组成，预计将显示出源于a）磁性离子的自旋与B）自旋和导电电子之间相互作用的新现象。 该项目中设计的新材料可能在自旋电子学领域有很强的应用，其中磁自旋增加了对电子设备的额外控制程度，在下一代高速和低功耗信息技术中具有巨大的潜力。揭示这种材料的性质，可以从溶液中沉积成膜，可以大大降低这种应用的成本。此外，在这些材料中可以实现具有基本科学兴趣的新现象，包括a）即使在非常低的温度下也不能有序的磁自旋，导致奇异的自旋模式，B）对齐以产生永磁体的自旋，以及c）控制材料内电子流动的磁自旋。当地高中学生将通过暑期课程参与研究，PI将继续重新设计普通化学，以便在课程早期向本科生介绍材料化学。通过与弗吉尼亚州汉普顿大学的合作，将对该项目中开发的材料进行近红外和中红外发射评估。汉普顿大学和斯坦福大学的本科生将学习如何通过在金属卤化物中掺入磁性杂质来控制光。技术概述卤化物钙钛矿的显著光电性能使其成为光伏和磷光体应用的优异候选者。然而，为这些应用探索的常见钙钛矿是钙钛矿。因此，具有类似光电性质并含有高密度自旋的金属卤化物基本上仍然未知。自旋电子学在下一代高速、低功耗信息技术中具有巨大的潜力，如磁阻效应在高密度数据存储中的应用。揭示这种现象的材料，可以从溶液中沉积的薄膜可以大大降低成本的应用。该项目由材料研究部的固态和材料化学以及电子和光子材料项目支持，通过开发新的合成路线来解决这一挑战，以实现磁性半导体在溶液中的自组装。预计这些新材料将在金属卤化物中显示出前所未有的现象，这些现象来自自旋-自旋和自旋-载流子相互作用。具体目标是：1）设计在有机或无机组分中包含自旋的新金属卤化物结构，2）开发具有分散电子带和可调载流子浓度的磁性金属卤化物，3）表征这些新材料的磁性，电荷传输和光电性能。从根本上说，金属卤化物中的新现象也将成为目标，包括磁挫折，自旋极化，以及巡回电子和嵌入的磁性子晶格之间的耦合。高中学生将参加夏季研究计划，PI将继续重新设计大一化学，在课程的早期向学生介绍材料化学。通过与弗吉尼亚州汉普顿大学的合作，将对该项目中开发的材料进行中红外和近红外发射评估。汉普顿大学和斯坦福大学的本科生将研究如何开发用于光子学的含镧系元素的金属卤化物。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 summaryThe remarkable optical and electronic properties of metal-halide semiconductors, which adopt the perovskite crystal structure, make them excellent candidates as component materials in solar cells and light emitting devices (e.g., LEDs). Perovskites that excel in these applications, however, are nonmagnetic. Thus, metal-halides with excellent optical and electronic properties and a high density of magnetic spins remain essentially unknown. With this project, supported by the Solid State and Materials Chemistry and Electronic and Photonic Materials programs in the Division of Materials Research, Professor Hema Karunadasa and her research group at Stanford University propose the design and synthesis of new magnetic semiconductors that form in solution. These materials, composed primarily of metal ions and halides, are expected to display new phenomena stemming from interactions between a) the spins of magnetic ions and b) the spins and conducting electrons. The new materials designed in this project could have strong applications in the field of spintronics, where magnetic spins add an additional degree of control over electronic devices, has great potential in next-generation high-speed and low-power information technologies. Revealing such properties in materials that can be deposited from solution as films could dramatically cut costs of such applications. Further, new phenomena of fundamental scientific interest may be realized in these materials, including a) magnetic spins that cannot order, even at very low temperatures, leading to exotic spin patterns, b) spins that align to create permanent magnets, and c) magnetic spins that control the flow of electrons inside a material. Local high-school students will participate in the research through summer programs and the PI will continue redesigning general chemistry to introduce undergraduate students to materials chemistry earlier in the curriculum. Through a collaboration with Hampton University, Virginia, materials developed in this project will be assessed for near- and mid-IR emission. Undergraduates at Hampton University and Stanford University will learn how to control light through the incorporation of magnetic impurities in metal-halides. Technical summaryThe remarkable optoelectronic properties of halide perovskites have rendered them excellent candidates for photovoltaic and phosphor applications. The common perovskites explored for these applications, however, are nonmagnetic. Thus, metal-halides that possess comparable optoelectronic properties and contain a high density of spins remain essentially unknown. Spintronics has great potential in next-generation high-speed and low-power information technologies, for example, magnetoresistance has applications in high-density data storage. Revealing such phenomena in materials that can be deposited from solution as films could dramatically cut costs of such applications. This project, supported by the Solid State and Materials Chemistry and Electronic and Photonic Materials programs in the Division of Materials Research, is addressing this challenge by developing new synthetic routes toward the self-assembly of magnetic semiconductors in solution. These new materials are anticipated to display unprecedented phenomena in metal-halides, derived from spin-spin and spin-carrier interactions. Specific objectives of the proposed work are: 1) the design of new metal-halide architectures that contain spins in the organic or inorganic components, 2) the development of magnetic metal-halides with dispersive electronic bands and tunable carrier concentrations, 3) the characterization of magnetic, charge transport, and optoelectronic properties of these new materials. Fundamentally new phenomena in metal-halides will also be targeted, including magnetic frustration, spin polarization, and coupling between itinerant electrons and an embedded magnetic sublattice. High-school students will participate in summer research programs and the PI will continue to redesign freshman chemistry to introduce students to materials chemistry earlier in the curriculum. Through collaboration with Hampton University, Virginia, materials developed in this project will be assessed for mid- and near-IR emission. Undergraduates at Hampton University and Stanford University will study how to develop lanthanide-containing metal-halides for applications in photonics.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.