Inducing multiferroicity in EuO thin films by epitaxial strain

五十多年来，微电子的器件速度和存储容量大约每两年翻一番。然而，继续这一进步已变得越来越困难。产生热量和基本量子力学限制的问题最终需要微电子技术的根本改变。传统技术最有希望的创新之一是自旋电子学，即在固态系统中使用电子自旋自由度。自旋晶体管潜在地提供了高处理速度和较低的散热，并且固有地具有非易失性存储器。因此，从长远来看，它们可能成为取代传统晶体管的候选者。对于这些器件的开发，允许有效地将自旋极化电流注入到半导体中并通过施加电场(多铁性)在室温下切换其磁化强度的材料可能是非常重要的。因此，我提出了一个研究计划，以实验研究有前途的材料Eu能否通过外延应变转变为一种新的状态，使这种高度自旋极化的铁磁半导体也具有多铁性。此外，外延应变还有望提高EuO的居里温度，为更高温度的多铁性提供了可能的途径。此外，还应研究在硅中外延集成应变EuO薄膜的可能性。所提出的研究计划不仅对自旋电子学的应用感兴趣，而且有助于更好地从根本上理解EuO中的外延应变效应。该项目采用了先进的分子束外延和现场监测技术。最重要的是，这包括具有原子层精度的薄膜生长、角度分辨光电子能谱，以及使用商业上无法获得的特定衬底材料。

For more than fifty years, device speeds and storage capacities in microelectronics have doubled approximately every two years. Continuation of this advancement, however, has become more and more difficult. The problems of heat generation and fundamental quantum mechanical limitations ultimately require a radical change in microelectronic technology. One of the promising innovations to conventional technology is spintronics, the use of the electron spin degree of freedom in solid-state systems. Spin-transistors potentially offer high processing speeds with reduced heat dissipation and inherently possess non-volatile memory. Therefore, in the long run, they could become candidates to replace conventional transistors. For the development of these devices, materials allowing for the effective injection of spin-polarized currents into semiconductors and switching their magnetization at room-temperature by applying electric fields (multiferroics) could be of high importance.Therefore, I propose a research program to investigate experimentally whether the promising material europium monoxide can be transformed into a novel state using epitaxial strain, rendering this highly spin-polarized ferromagnetic semiconductor also multiferroic. The epitaxial strain is additionally expected to enhance the Curie temperature of EuO providing a possible route to higher-temperature multiferroics. Furthermore, possibilities to epitaxially integrate strained EuO films in silicon shall be investigated. The proposed research program is not only of interest for spintronic applications, but could also contribute to a better fundamental understanding of epitaxial strain effects in EuO. The project employs advanced molecular beam epitaxy and in-situ monitoring techniques. Most importantly, this includes film growth with atomic layer precision, angle-resolved photoemission spectroscopy and utilization of specific, commercially not available substrate materials.