Towards Development of Indigenous Differential Spectroscopic Instruments

Abstract

Layered 2D semiconductors and magnets demonstrate novel excitonic physics. Their magnetic properties can be effectively studied at low fields using differential spectroscopy techniques such as Faraday effect and magneto-optic Kerr effect. The precision of these techniques can be further improved by the use of the Sagnac effect, which is only sensitive to magnetic effects. In this thesis, a broadband magneto-optic Kerr effect measurement technique, based on the Sagnac effect, is proposed on the basis of Jones matrix analysis. Its assembly and testing procedure is described. An effective technique to characterise candidate samples for Kerr spectroscopy is scanning photoluminescence microscopy. Improvements to the speed and resolution of an existing scanning photoluminescence microscope, used to characterise monolayer semiconductors are presented. Photoluminescence scans of tungsten disulphide flakes, highlighting monolayer regions, are demonstrated. In order to carry out these magneto-optic measurements over a wide spectral range, broadband LED light sources, and compact magnetometers are highly desirable. The design and construction of a broadband LED source, with emission from 400 nm to 1000 nm, is described. Its suitability for spectroscopic measurements, in terms of stability, is shown. Additionally, the design and construction of a compact, cost-efficient 0 T to 0.5 T magnetometer, and its interfacing with SCPI, is presented.