Molecular beam epitaxy and magnetotransport of manganese monosilicide layers on (111) silicon substrates

我们将发展分子束外延技术在Si(111)衬底上生长单硅化锰层，并对这些层的结构、磁性和磁输运性质进行表征。MnSi是一种磁性金属，具有立方B20晶体结构，没有反转对称性。这导致了复杂的磁输运行为和依赖于温度和外部磁场的丰富的磁相图。最有趣的相是由约20 nm周期的Skyrmion晶格组成，最近在体相MNSI中用中子散射观察到。我们的项目目标是外延MNSI和MNSI/Si层结构的生长。将进行晶体性质以及面内和跨面磁输运的基础研究。材料的加工将被开发，以便能够实现和研究具有与Skyrmion晶格相当的尺寸的结构。在这种硅基材料体系中，有序磁态和部分自旋极化电流的相互作用产生了新的自旋电子学效应。分子束外延可以生长出高质量的MnSi/Si(111)薄膜。需要通过初始固相外延工艺形成薄的MnSi种子层。这种种子层和适当的分子束外延条件能够使MnSi逐层生长，并防止其他硅化物相的形成。将对这些层进行表征和优化，以实现单晶度、平整度和低缺陷密度。外延硅帽层的异质外延旨在防止形成锰氧化物和界面缺陷。将开发一种用于隧道传输和尺寸小于100 nm的霍尔棒结构的电子束光刻工艺。将进行宏观和介观测试结构的磁测量和电子研究，并为未来高质量的MNSI/Si(111)自旋电子结构奠定基础。

We will develop methods for molecular beam epitaxy of Manganese monosilicide (MnSi) layers on Si(111) substrates and characterize the structural, magnetic and magnetotransport properties of these layers. MnSi is a magnetic metal with a cubic B20 crystal structure without inversion symmetry. This results in a complex magnetotransport behavior and a rich magnetic phase diagram which depends on temperature and external magnetic field. The most interesting phase, which consists of a Skyrmion lattice of about 20 nm period, has been recently observed by neutron scattering in bulk MnSi. Our project objectives are the growth of epitaxial MnSi and MnSi/Si layer structures. Fundamental studies of crystal properties and in-plane and cross-plane magnetotransport will be performed. Processing of the material will be developed so that structures with comparable dimensions to the skyrmion lattice can be realized and studied. The interaction of ordered magnetic states and partly spin-polarized current within nanostructures promise novel spintronic effects in this Si-based material system.MnSi/Si(111) layers of high crystal quality can be grown by MBE. A thin MnSi seed layer needs to be formed by an initial solid phase epitaxial process. This seed layer and adequate MBE conditions then enable layer-by-layer growth of MnSi and prevent the formation of other silicide phases. The layers will be characterized and optimized for single crystallinity, smoothness and low defect density. Heteroepitaxy of an epitaxial Si cap layer is intended to prevent formation of Mn oxides and interface defects. An e-beam lithography process for tunneling transport and Hall bar structures with sub-100nm dimensions will be developed. Magnetometry and electronic studies of macroscopic and mesoscopic test structures will be performed and form the foundation to future high quality MnSi/Si(111) spintronic structures.