Author : Genevieve Clark
Publisher :
ISBN 13 :
Total Pages : 104 pages
Book Rating : 4.:/5 (18 download)
Book Synopsis Optics and Optoelectronics of Atomically Thin Magnets and Semiconductors by : Genevieve Clark
Download or read book Optics and Optoelectronics of Atomically Thin Magnets and Semiconductors written by Genevieve Clark and published by . This book was released on 2018 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the discovery of graphene, layered van der Waals materials have become one of the most active subjects of study. The array of available atomically thin materials has expanded rapidly beyond graphene, encompassing a wide variety of physical properties ranging from insulators like hexagonal boron-nitride, to semiconductors such as MoS2 and superconductors (ie NbSe2) to name a few. These materials are of significant fundamental interest, since they offer the first opportunity to study physical phenomena in a truly two-dimensional system, while showing layer-dependent emergent properties unavailable in any other class of materials. They also offer a potential answer to the increasing demand for nanostructured materials, as current electronic and magnetic devices approach the nanoscale, and devices based on quantum mechanical phenomena rise to the forefront of emerging technology. Here, I employ optical and optoelectronic characterization to study two different types of 2D materials - few-layer flakes of the layered magnetic insulator CrI3, and monolayer flakes of semiconducting WSe2. The first three chapters of this thesis focus on the isolation, characterization, and control of magnetism in mono- and few-layer flakes of CrI3. Bulk crystals of CrI3 are known to be ferromagnetic insulators with large predicted magnetocrystalline anisotropy, essential in order to stabilize low dimensional magnetic order against thermal fluctuations. Optical characterization of monolayer CrI3 reveals robust ferromagnetic behavior, while bilayer and trilayer flakes show layered antiferromagnetic behavior, with strong intra-layer ferromagnetism and antiferromagnetic inter-layer coupling. Van der Waals heterostructure devices based on bilayer CrI3 flakes allow gate-dependent control of magnetic behavior in bilayer CrI3 flakes. This work demonstrates both the first truly two-dimensional magnetic material and electrostatic control of magnetic phase in bilayer CrI3. In chapter four, I discuss the optical properties of both intrinsic and defect-bound excitons in monolayers of WSe2 scalably grown using chemical vapor deposition (CVD). While the majority of optical studies utilize exfoliated flakes of WSe2, this time-consuming and non-scalable process will limit future studies of this material. I discuss a scalable, direct method of monolayer growth that yields flakes with high optical quality, assessed using low-temperature optical characterization of the intrinsic excitons in this material. I then discuss the discovery of a new type of single photon emitter found in the monolayer flakes, thought to arise from single intrinsic excitons localized to defects within the layers. Finally, these two materials are combined to form spintronic devices based on van der Waals heterostructures of bilayer CrI3 and monolayer WSe2 described in chapter 5.
