Micro and Nano Fabrication of Structures for Light-Matter Interaction

Abstract

Nanofabrication encompasses processes and techniques used to create structures with features smaller than 100 nm, enabling precise design and manipulation of materials at the atomic and molecular level. Nanoscience and nanofabrication have made significant contributions to various industries, including electronics, materials science, and catalysis. A notable achievement in nanoscience has been the discovery and study of two-dimensional (2D) materials, which possess unique properties due to their weak atomic bonds and high surface-to-volume ratio. These materials offer flexibility, mechanical strength, high conductivity, and tunable optical properties. They have become essential tools for investigating optical phenomena at the atomic scale.This thesis focuses on optimizing sample preparation through controlled parameter modifications and subsequent characterization using techniques available at CIC nanoGUNE. The research combines fabrication techniques with 2D materials, primarily in the field of nanooptics, which explores the interaction between light and matter at the nanoscale. Techniques like mechanical exfoliation, atomic force microscopy, Raman spectroscopy, and various transfer methods are employed to obtain and manipulate thin layers of materials, including heterostructures. Sample fabrication involves lithographic techniques such as direct laser writing lithography and electronbeam lithography, allowing versatile and adaptable designs without the need for physical masks. Material deposition techniques like evaporation and sputtering, as well as material removal techniques like reactive ion etching and ion bombardment, are employed in the fabrication process.The potential of these techniques is demonstrated through the fabrication of samples on different substrates and exfoliated flakes, enabling detailed studies and collaborations. Challenges encountered in the fabrication process, such as the proximity effect in electron beam lithography and charge accumulation on insulating substrates, require optimization and specific approaches to overcome.The thesis also explores the application of 2D material techniques in the study of strain on hybrid perovskites, focusing on the tunability of their optical properties through mechanical strain. The research investigates the micro photoluminescence of 2D lead bromide HOIP sheets subjected to biaxial strain, revealing the emergence of distinct photoluminescence peaks at low temperatures. The findings highlight the potential of strain engineering for the design of optoelectronic and strain-based sensing devices using 2D HOIPs. Furthermore, the thesis explores the coupling regime in classical microcavities constructed using 2D materials, particularly hexagonal boron nitride (hBN). Strong coupling between molecular vibrations and microcavity modes has been extensively studied, while the coupling between phonons and microcavity modes offers intriguing possibilities. By exfoliating hBN and creating thin layers, the study demonstrates controllable achievement of strong coupling and even ultrastrong coupling with minimal amounts of phononic material. The findings indicate that phonon polaritons formed in classical cavities can modify the properties of polar crystals, presenting a versatile platform for investigating the coupling between photons and phonons.