Polar magneto-optical Kerr effect spectroscopy with a microscope arrangement for studies on 2D materials

• Published in: Review of scientific instruments Vol. 95; no. 8
• Main Authors: Das, Dibyasankar, Ghosh, Sandip
• Format: Journal Article
• Language: English
• Published: United States American Institute of Physics 01.08.2024
• Subjects: Circular polarization; Ellipsometry; Ellipticity; Excitons; Flakes; Kerr magnetooptical effect; Low temperature; Matrix methods; Spatial resolution; Spectrum analysis; Two dimensional materials
• ISSN: 0034-6748; 1089-7623; 1089-7623
• DOI: 10.1063/5.0209323

We describe a setup for magneto-optical Kerr effect (MOKE) spectroscopy suitable for Kerr rotation (ϕ) and ellipticity (η) measurement on microscopic samples, such as flakes of two-dimensional materials. A spatial resolution of ∼25 μm, limited by the demagnified monochromator exit slit image, was achieved. The use of mirrors allows for measurement in polar MOKE geometry with a conventional electro-magnet, without requiring holes in the magnet pole pieces. The microscope-like optics also has a 90° twisted periscope arrangement of two mirrors that helps transport light without change in its circular polarization state. A Jones matrix analysis of the setup brings out the influence of the beam-splitter on the measured signals. Its correction requires the ellipsometry parameters of the beam-splitter in transmission mode, which were measured separately. The working of the setup is tested by measuring the ϕ and η spectra of 2H-WS2 flakes at low temperature, verifying them using Kramers–Kronig analysis and extracting the Landé g-factor of the ground state exciton from them.