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

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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.