NANOPATTERNING OF FREE-STANDING VAN DER WAALS HETEROSTRUCTURES USING CHARGED PARTICLES

Lateral confinement in two-dimensional (2D) transition metal dichalcogenides (TMDs) enables one-dimensional structures with tunable band structures, offering new opportunities in nanophotonics and optoelectronics. However, achieving such confinement with high spatial and depth resolution in stacked van der Waals heterostructures remains challenging. In this thesis, we demonstrate selective nanopatterning of free-standing hBN-encapsulated graphene and semiconducting TMDs using focused helium ion beams. By leveraging differences in electronic and nuclear stopping powers, we achieve layer-specific modification where the active layer (graphene or TMD) is altered while the surrounding hBN remains intact. Combining experimental nanopatterning, (S)TEM characterization, and SRIM-based ion–solid interaction simulations, we establish a framework for depth-selective irradiation. The resulting lateral confinement in TMDs enables nanoscale tuning of optical responses, probed via monochromated electron energy-loss spectroscopy (EELS). We further demonstrate confined excitonic and plasmonic resonators, showcasing a robust, top-down route to engineer functional nanophotonic elements within encapsulated 2D material systems.

Author dc:creator

• JAGADESH RANGARAJ

• Excitonic
• Plasmonic
• Characterization
• Nanopatterning
• Lateral confinement
• Selective

Licence

• https://scholarbank.nus.edu.sg/bitstreams/7ee1e73b-f643-4e1f-815a-a68f4863164a/download