Collaborative Research: Spintronics Without Spin Injection

CMOS技术的持续扩展受到各种方法的推动，包括基于自旋的电子（或“自旋电子学”），这是由于低功耗操作的潜在收益，以及实现新形式的非易失性芯片上数据存储的前景。然而，自旋电子器件通常表现出较差的磁阻值，除了在低温下，并且通常存在有关其可制造性的实际问题。因此，自旋电子学对技术和社会的全部潜在影响仍未实现。在复合氧化物上沉积的外延形成的石墨烯层中诱导高度自旋极化的能力是本研究的主要目标；一个将允许开发高性能，非易失性，基于自旋的设备，能够在室温以上工作。这种进步的社会和经济效益是巨大的，不仅允许继续使用更小、更便宜和更快的计算，而且还使大规模并行、低功耗和容错的计算机体系结构的发展成为可能。研究生将接受跨学科方面的培训，了解表面/界面化学，电荷和自旋输运以及器件物理之间的基本关系。这种指导还延伸到通过布法罗大学、内布拉斯加大学林肯分校和北德克萨斯大学现有的、经过验证的项目招收本科生和高中生。在新一代后cmos纳米电子学领域，自旋电子器件的技术挑战包括实现高保真的自旋极化载流子注入到非磁性半导体中，以及；实现磁性操纵的电气方案，同时不损害自旋电子学提供的可能的能量增益。该计划提供了一个解决方案，通过实现实用的、基于石墨烯的自旋电子器件，基于工业兼容的石墨烯生长方法，并在室温或高于室温下工作。这些器件的特点是在磁性/多铁性氧化物衬底上直接生长高质量的石墨烯，并将利用石墨烯通道中通过与衬底的相互作用诱导的自旋极化，从而消除了对铁磁电极有效自旋注入的需要。此外，器件将通过施加在绝缘氧化物上的电场来开关，从而确保低功耗运行。本项目结合了石墨烯/氧化物异质结形成的界面化学，其对石墨烯自旋极化的影响，以及自旋场效应晶体管的开发和测试。这些器件基于石墨烯/氧化物异质结的直接生长，包括Co3O4(111), Cr2O3（0001）和其他有序的多铁氧化物。目标是对表面化学如何影响自旋输运有一个基本的了解，并产生可制造的基于石墨烯的自旋电子器件，能够在室温以上的操作中表现出卓越的性能（MR200%）。

The continued scaling of CMOS technology is being driven by various approaches including spin-based electronics (or 'spintronics') due to potential gains in low-power operation, and by the prospect of realizing new forms of non-volatile, on-chip data storage. However, spintronic devices typically exhibit poor magnetoresistive values, except at cryogenic temperatures, and there are often practical issues regarding their manufacturability. Consequently, the full potential impact of spintronics on technology and society has remained unrealized. The ability to induce a high degree of spin polarization in epitaxially-formed graphene layers, deposited on complex oxides, is a major goal of this research; one that will allow the development of high performance, non-volatile, spin-based devices, capable of operating above room temperature. Social and economic benefits of such advances is huge, allowing not only the continuation of smaller, cheaper, and faster computing, but also making possible the development of massively-parallel, yet low-power and fault-tolerant, computer architectures. Graduate students will be trained in the interdisciplinary aspects of understanding fundamental relationships between surface/interface chemistry, charge and spin transport, and device physics. This mentoring also extends to the recruitment of undergraduate and high school students through existing, proven programs at the University of Buffalo, the University of Nebraska-Lincoln and at the University of North Texas.In the interest of a new generation of post-CMOS nanoelectronics, technological challenges of spintronic devices include achieving high-fidelity spin-polarized carrier injection into a nonmagnetic semiconductor, and; realization of electrical schemes for the manipulation of magnetism while not compromising the possible energy gains offered by spintronics. This program provides a solution by realizing practical, graphene-based spintronic devices, based on industry-compatible graphene growth methods and operating at or above room temperature. These devices feature directly-grown, high-quality graphene on magnetic/multiferroic oxide substrates, and will exploit the spin polarization induced in the graphene channel through its interaction with the substrate, thereby obviating the need for efficient spin injection from ferromagnetic electrodes. The devices will furthermore be switched by means of the electric field applied across insulating oxides, thereby ensuring low-power operation. This project combines studies of the interfacial-chemistry of graphene/oxide hetero-junction formation, its effects on graphene spin polarization, and the development and testing of spin-field effect transistors. These devices are based on the direct growth of graphene/oxide heterojunctions, including Co3O4(111), Cr2O3(0001), and other ordered multiferroic oxides. The goal is to have a fundamental insight into how surface chemistry impacts spin transport, and also to yield manufacturable graphene-based spintronic devices, capable of exhibiting superior per-formance (MR200%) in operation above room temperature.