Maria Barra Ph.D. Thesis Defense: Micro and Nano Fabrication of Structures for Light-Matter Interaction

Who: Maria Barra, Pre-doctoral Researcher, Nanodevices

Place: CFM Auditorium

Date: Thursday, 21 September 2023, 12:00

Nanofabrication includes those 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 and materials science. A notable achievement 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 a essential platform for investigating optical phenomena at the atomic scale. This thesis focuses on optimization of sample preparation using techniques available at CIC nanoGUNE. The research combines fabrication techniques with 2D materials, primarily in the field of nanooptics. Techniques like mechanical exfoliation, atomic force microscopy or Raman spectroscopy, are employed to obtain and characterize thin layers of materials, and the preparation of heterostructures. Sample fabrication involves lithographic techniques such as direct laser writing lithography and electron beam lithography, allowing versatile and adaptable designs. The potential of these techniques is demonstrated through the fabrication of samples on different substrates and exfoliated flakes.

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 coupling regime in classical microcavities constructed using 2D materials, particularly hexagonal boron nitride (hBN), is also explored. 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. 

 

Supervisors: Luis Hueso and Rainer Hillenbrand.

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