Spinterface Engineering for Efficient Device Operation (SPEEDO)

分子自旋电子学是一个新兴的研究领域，它试图建立在传统自旋电子学（例如所有现代硬盘驱动器中的读头）和有机电子学（例如柔性显示器）的巨大成功的基础上，以生产诸如有机自旋晶体管，柔性存储器元件和自旋led等设备。有机半导体分子（OSCs）主要由C、H、N和O等轻元素组成，这意味着它们与电子自旋的相互作用非常弱——这是自旋电子技术除了电子电荷外还能操纵的基本性质。因此，osc被认为是很有前途的材料，用于希望通过与铁磁材料的界面传递自旋极化电子（自旋注入）或将它们从一个铁磁电极传输到另一个铁磁电极（自旋输运）的设备中。osc的其他有益特性包括其物理和化学柔韧性以及以低成本大量生产它们的能力。为了克服第一代有机器件表现出的不良和不可复制的性能，越来越清楚的是，需要更好地了解osc与支持它们的铁磁性衬底之间的相互作用。这种有机/铁磁界面或“spinterface”上的化学相互作用可能导致不良影响，如分子扭曲、自旋极化减少和杂化电子态的出现。该项目的目的是通过使用一束激发氦原子作为表面电子和磁性质的非常敏感的探针来提供这些缺失的知识。这种方法的表面灵敏度意味着它是研究分子在表面吸附的理想方法，使其应用于有机自旋电子学既新颖又及时。除了常见的OSCs，如C60和金属酞菁外，具有两层结构的更奇特的“双层”分子也将被研究。理论预测这些分子可以作为非常有效的自旋过滤器，但这需要实验证实。氦气技术还将使spinterface具有有利于设备性能的特性。例如，正如我们之前所展示的，简单原子（如H和B）的吸附可以钝化铁磁性材料（如Fe3O4）表面的电子状态，并恢复理想的体性质（如半金属性）。基于这些优化的自旋界面，原型器件如有机自旋阀和磁性隧道结将被制造出来，目的是展示增强的器件性能。一种新的方法真空键合工艺也将被开发，以允许高质量的接口被合并在两个器件电极。这开启了制备有机器件的可能性，其中顶部和底部电极都由铁磁性氧化物组成，这一概念迄今尚未得到令人满意的证明。

Molecular spintronics is an emerging research field that seeks to build on the enormous successes of conventional spintronics (e.g. read-heads in all modern hard disk drives) and organic electronics (e.g. flexible displays) to produce devices such as organic spin transistors, flexible memory elements, and spin LEDs. Organic semiconducting molecules (OSCs) are mainly composed of light elements such as C, H, N, and O which means that they interact very weakly with an electron's spin--this is the fundamental property that spintronic technologies manipulate in addition to electronic charge. As such, OSCs are considered promising materials for use in devices in which it is desirable to pass spin-polarised electrons across an interface with a ferromagnetic material (spin injection) or to transport them from one ferromagnetic electrode to another (spin transport). Other beneficial properties of OSCs include their physical and chemical flexibility and the ability to produce them at low cost in large quantities.To overcome the poor and irreproducible performance demonstrated by first-generation organic devices, it has become increasingly clear that a much better understanding of the interaction between OSCs and the ferromagnetic substrates that support them is needed. The chemical interaction at this organic/ferromagnetic interface, or 'spinterface', can lead to undesirable effects such as molecular distortion, a reduction in spin polarisation, and the appearance of hybridised electronic states. The aim of this project is to provide this missing knowledge by using a beam of excited helium atoms as a very sensitive probe of surface electronic and magnetic properties. The surface sensitivity of this approach means that it is ideal for studying the adsorption of molecules on surfaces making its application to organic spintronics both novel and timely. In addition to common OSCs such as C60 and the metal phthalocyanines, more exotic 'double-decker' molecules that have a two-layer structure will also be investigated. Theory predicts that these molecules could act as very efficient spin filters however this needs confirming experimentally.The helium technique will also enable spinterfaces to be engineered with properties that are beneficial to device performance. For example, as we have shown before, the adsorption of simple atoms such as H and B can passivate the electronic states found at the surface of a ferromagnetic material such as Fe3O4 and recover desirable bulk properties such as half-metallicity. Based on these optimised spinterfaces, prototypical devices such as organic spin valves and magnetic tunnel junctions will be fabricated with the aim of demonstrating enhanced device performance. A novel method vacuum bonding process will also be developed to allow high-quality interfaces to be incorporated at both device electrodes. This opens up the possibility of preparing organic devices in which both the top and bottom electrodes consist of ferromagnetic oxides, a concept that has not been satisfactorily demonstrated to date.