Inducing multiferroicity in EuO thin films by epitaxial strain

50多年来，微电子设备的速度和存储容量大约每两年翻一番。然而，这种进步的继续已经变得越来越困难。生热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。自旋电子学是对传统技术的一项有前途的创新，它利用了固态系统中的电子自旋自由度。自旋晶体管潜在地提供具有减少的热耗散的高处理速度，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。为了开发这些器件，材料允许将自旋极化电流有效地注入半导体，并通过施加电场在室温下切换它们的磁化因此，我提出了一个研究计划，以实验研究是否可以使用外延应变将有前途的材料一氧化铕转化为新的状态，使得这种高度自旋极化的铁磁半导体也是多铁性的。另外，预计外延应变，以提高居里温度的EuO提供一个可能的路线，以更高的温度多铁性。此外，外延集成应变氧化铕薄膜在硅的可能性进行了研究。建议的研究计划不仅是感兴趣的自旋电子学应用，但也可能有助于更好地理解外延应变效应的EuO。该项目采用先进的分子束外延和原位监测技术。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和利用特定的商业上不可用的衬底材料。

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.