Surface Properties of Spintronic Materials Probed Using a Spin-Polarised Metastable Helium Beam

Since the isolation of graphene in 2004, there has been an increasing drive to tailor this and other 2D materials for spintronic applications due to their unique electronic properties. Analysis of the surface Fermi-level spin polarisation of 2D materials is crucial in designing spintronic devices, and characterising this property requires extremely surface sensitive techniques. One such approach, metastable de-excitation spectroscopy (MDS), involves the use of helium atoms prepared in the 23S state to analyse the surface density of states. This thesis presents the first set of results from an extension to this technique known as spin-polarised metastable emission electron microscopy (SPMEEM), in addition to detailed studies of several materials systems relevant to the development of spintronic devices.

After an introduction and review of how 2D materials are potential candidates for spintronics, a detailed description of MDS is given in Chapter 3 with Chapter 4 outlining other experimental approaches and systems used throughout this project. Chapter 5 reports a detailed study of domain structures at the surface of Fe3O4(001) probed using SPMEEM. The use of SPMEEM to observe the spin reorientation transition in Fe3O4(001) is also outlined. Chapter 6 explores how graphene grown on silicon carbide could be modified for spintronic applications through the adsorption of hydrogen and intercalation of heavy metallic species. Chapter 7 presents results from a study of the organic semiconducting molecule 6T on manganite (LSMO) substrates, a system of interest in organic spintronics. Finally, the thesis concludes with a chapter on conclusions and future work.