Optical modification of 2D materials

Two-dimensional layered materials, characterized by their atomic thickness and diverse properties, are a promising material platform for advancing many technological fields, including physics, quantum technologies and medicine. In the past twenty years, the family of two-dimensional materials has expanded and nowadays encompasses thousands of materials that range from insulators to conductors, with physical properties for applications across the range.

However, their industrial scale applications still face issues, mainly stemming from the difficulty of obtaining cost-effective and fast large-scale fabrication methods. Optical modification methods are processes that utilize the energy of light to drive fabrication and property modification processes, such as doping and patterning. They provide a great alternative to conventional fabrication methods as they are sustainable, fast, cheap, and can provide highly localized modification without the use of masks.

This thesis focuses on advancing the field of optical modification by exploring optical defect engineering of both monolayer and multilayer heterostructure transition metal dichalcogenides. Femtosecond laser irradiation is found to enhance the nonlinear optical responses of transition metal dichalcogenide flakes by resonances with defect states while also creating three-dimensional structures in the flake. On the other hand, continuous wave irradiation of transition metal dichalcogenide heterostructures is found to simultaneously modify both constituent materials at different rates, leading to enhanced photoluminescence and drastic changes in electrical properties.

These findings not only deepen our understanding of the interaction between light and two-
dimensional materials but also highlight the untapped potential of optical modification methods. By applying the results in practical applications, this work further establishes optical modification methods as a true alternative for scalable and sustainable technologies that harness the unique properties of two-dimensional materials for next-generation innovations.