Show simple item record

dc.rights.licenseRestricted to current Rensselaer faculty, staff and students. Access inquiries may be directed to the Rensselaer Libraries.
dc.contributorWang, G.-C. (Gwo-Ching), 1946-
dc.contributorShi, Jian
dc.contributorUllal, Chaitanya
dc.contributorSundararaman, Ravishankar
dc.contributor.authorValdman, Lukas
dc.date.accessioned2021-11-03T09:21:03Z
dc.date.available2021-11-03T09:21:03Z
dc.date.created2021-01-21T12:36:30Z
dc.date.issued2020-08
dc.identifier.urihttps://hdl.handle.net/20.500.13015/2587
dc.descriptionAugust 2020
dc.descriptionSchool of Engineering
dc.description.abstractElectron orbiting around its core produces orbital magnetic moment. Each electron also has its own intrinsic angular momentum, that is, spin. The overall magnetic moment is a combination of the orbital and spin magnetic moments. In a magnetic material, there is a tendency to align the magnetic moments along a direction of the applied external magnetic field. Novel magnetic materials are fundamental to the next technological advancements. Spintronics or spin electronics opens door to new devices exploiting the electron’s spin property in addition to the charge degree of freedom. The potential applications include data storage, data processing and magnetic sensing. There is not only a need for novel magnetic materials with its Curie temperature above 300 K, but also for appropriate characterization tools allowing to study the emerging magnets.
dc.description.abstractThe magneto-optical effects can serve to effectively probe the spintronic materials due to the strong interaction between photons and electrons’ spin. This is demonstrated by observation of Faraday transmission and Kerr reflection effects in materials exhibiting the magnetic ordering. First part of this thesis focuses on utilization of the magneto-optical Kerr effect (MOKE) for construction and testing of MOKE microscope working in the Longitudinal mode. Recording of hysteresis loops from a continuous Ni(001) film and a continuous polycrystalline Ni film confirmed the successful operation of the microscope. Furthermore, discontinuous magnetic materials can be investigated with the MOKE microscope with its spatial resolution of 5 μm. In addition, the probing area was decreased from 0.8 mm to about 10 μm, enabling to collect a weak magnetic signal from ultrathin flakes as small as 10 μm.
dc.description.abstractVanadium disulfide (VS2) is a transition metal dichalcogenide predicted by density functional theory to possess magnetic behaviour at room temperature. The intrinsic magnetic ordering is thickness dependent, when the ultrathin VS2 is ferromagnetic and the bulk VS2 is paramagnetic. The ultrathin H-phase VS2 is a direct band gap semiconductor, making it a potential candidate in the field of spintronics. The second part of this thesis describes the synthesis and characterization of vanadium disulfide ultrathin flakes. Chemical vapor deposition-based growth recipe was developed producing ultrathin flakes with aspect ratio in the range of ~ 6×10^3, one of the largest reported in the literature. The thinnest flakes were two single layers thick and less than 2 μm large, as detected with atomic force microscopy. The (001) out-of- plane orientation was confirmed by X-ray diffraction. The chemical composition of our samples was investigated by energy dispersive spectroscopy and the V to S ratio was determined to be 1.28 to 2, indicating a vanadium rich phase. Finally, the MOKE microscope was employed to study the predicted room temperature ferromagnetism. While the microscope was able to locate particular VS2 ultrathin flakes, overcoming the major bottleneck of previous magnetic studies, no hysteresis loops were recorded. This may be caused by the incorrect stoichiometry, inability to grow large coverage of one to few monolayers thick VS2 and atmosphere contamination.
dc.language.isoENG
dc.publisherRensselaer Polytechnic Institute, Troy, NY
dc.relation.ispartofRensselaer Theses and Dissertations Online Collection
dc.subjectMaterials engineering
dc.titleConstruction of moke microscope for magnetic studies of vanadium disulfide flakes
dc.typeElectronic thesis
dc.typeThesis
dc.digitool.pid180255
dc.digitool.pid180256
dc.digitool.pid180257
dc.rights.holderThis electronic version is a licensed copy owned by Rensselaer Polytechnic Institute, Troy, NY. Copyright of original work retained by author.
dc.description.degreeMS
dc.relation.departmentDept. of Materials Science and Engineering


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record