Author : Michael Jonathon Newburger
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (133 download)
Book Synopsis Measurement and Manipulation of Spins and Magnetism in 2D Materials and Spinel Oxides by : Michael Jonathon Newburger
Download or read book Measurement and Manipulation of Spins and Magnetism in 2D Materials and Spinel Oxides written by Michael Jonathon Newburger and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advancements in spintronics rely on materials which exhibit stable magnetization or long-lived spin states that can be easily manipulated or probed. One class of two-dimensional (2D) materials, the monolayer transition metal dichalcogenides (TMDs) have gained significant interest due to their large spin-orbit coupling which leads to the existence of inequivalent, spin-split valleys in the band structure and predictions of long-lived spin-valley lifetimes. Furthermore, the TMDs exhibit unique optical selection rules which allow for selective control and manipulation of spin and valley polarization by helicity of light. In addition, due to their weak van der Waals coupling, these materials can be easily picked up and stacked into heterostructures with other 2D or three dimensional (3D) materials without the need to match lattice constant or growth conditions. Here, the strength of one material can surmount the weaknesses of another system, and such heterostructures have been utilized to control exciton diffusion, enhance spin/valley lifetimes, and even induce proximity spin-orbit coupling and ferromagnetism. In this thesis, we focus on measuring the spin/valley dynamics in TMD monolayers and heterostructure devices. Using time-resolved Kerr rotation (TRKR) microscopy, we observe long-lived (>5 ns) spin/valley lifetimes and a complex spatial dependence of spin/valley density in monolayer WS2 flakes. Comparisons to photoluminescence (PL) microscopy allow us to elucidate the roles that resident carriers and dark trion formation play in this spatial dependence and the stabilization of spin-valley lifetime. We extend these techniques to heterostructure devices of monolayer WSe2 and graphene where we reveal an ultrafast quenching of spin-valley signal at the WSe2/graphene heterojunctions. Complementary measurements of PL and photoconductivity demonstrate an efficient, electron dominated charge transfer into graphene, from which we conclude that the quenching of the spin-valley signal is due to charge mediated spin transfer into graphene. Additionally, we explore the growth of complementary magnetic materials by molecular beam epitaxy. Specifically, we demonstrate growth of MgAl0.5Fe1.5O4 (MAFO), a low damping, ferrimagnetic insulator which is an ideal candidate for the demonstration of proximity effects in 2D materials. We find that highly crystalline films of MAFO can be grown by MBE and utilize alternating layer epitaxy to alter the distribution of Fe in the crystal lattice, from which we observe a significant change in the saturation magnetic moment.
