Publication Date

Spring 2026

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Physics and Astronomy

Advisor

Christopher Smallwood; Ehsan Khatami; Hiu Yung Wong

Abstract

Atomically thin semiconductors and moir’e heterostructures provide an important platform for studying quantum phenomena shaped by reduced dimensionality, interlayer coupling, strain, and local structure. In MoS2, the transition from bulk to monolayer form changes the material from an indirect to a direct band gap, while stacked and strain-engineered systems can produce spatially varying moir’e potentials on nanometer length scales. Because these effects are highly localized, conventional far-field optical spectroscopy is often limited in its ability to resolve them directly. This thesis explores superresolution vibrational spectroscopy as a route toward probing local behavior in atomically thin semiconductors and moir’e heterostructures. Far-field Raman spectroscopy is first used to characterize exfoliated MoS2 samples and examine phonon modes that reflect material structure and local properties. The work then motivates the use of tip-enhanced Raman spectroscopy to achieve improved spatial resolution for nanoscale spectroscopic studies. Tip-enhanced Raman spectroscopy is implemented using a combined atomic force microscopy and Raman system. A carbon nanotube test sample is used to evaluate the spatial performance of the technique before applying it to low-dimensional semiconductor systems. From measured line profiles, an effective spatial resolution of approximately 18 nm is obtained, demonstrating a substantial improvement over diffraction-limited Raman spectroscopy. Overall, this work establishes an experimental foundation for using superresolution Raman spectroscopy to study atomically thin semiconductors and moir’e heterostructures, with the broader goal of resolving how local structure influences vibrational and optical behavior in engineered quantum materials.

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