Fabrication and process optimization for functional 3D periodic nanolattices

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2023-12

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This research focuses on the development and analysis of advanced nanolattices and three-dimensional (3D) nanostructures, showing their significance in nanophotonics, integrated circuits, lasers, optical systems, and various other applications. Nanolattices are characterized by their periodic lattice arrangement, hollow-core, and thin-shell elements, are fabricated using thin-film deposition on 3D polymer templates. These structures offer immense potential in mechanical, optical, and thermal applications, due to their unique properties. However, a major challenge in their fabrication is the residual polymer left within the nanolattice, which can impede their performance. To address this, the study investigates three different polymer template removal techniques, including oxygen plasma etching, solvent dissolution, and thermal desorption, to determine their effectiveness in eliminating residual polymer. The removal rates and effectiveness of each method are quantitatively analyzed using spectroscopic ellipsometry, a technique that precisely measures the effective refractive index and calculates the amount of residual polymer. The findings reveal that thermal treatment is the most effective in template removal, providing a path to enhance nanolattice fabrication for various applications. Additionally, the research utilizes a three-phase Maxwell–Garnett effective medium model to estimate the residual polymer in nanolattices. Parallelly, the research delves into the fabrication of 3D nanostructures, specifically opal structures, which are spatially aligned to an array of holes defined in the photoresist. This approach employs colloidal lithography to pattern a hexagonal array of holes, guiding the assembly of colloidal particles into 3D opal structures. This method ensures the alignment of the 3D opal structures with the 2D hole array, enhancing spatial-phase coherence and minimizing defects. The polymer patterns serve as a sacrificial template for atomic layer deposition, enabling the creation of free-standing nanolattices. These nanolattices are subsequently coated with a thick layer of titanium oxide, demonstrating their mechanical stability. The resulting structures boast high porosity, essential for creating low-index materials in nanophotonics. Additionally, the study incorporates nature-inspired nanostructures, employing biomimetic principles to enhance the functionality and efficiency of these materials. These nature-inspired designs, mimicking the structures found in natural organisms, provide solutions for light manipulation and structural resilience. These nanostructures, with controlled height and precise deposition, are ideal for applications in Bragg reflectors, nanophotonics, and optical multilayers, marking a significant advancement in the field of nanostructured materials. The study's findings on template removal, 3D nanostructure fabrication, and biomimetic design open new avenues for research and development in this rapidly evolving field, promising enhancements in the efficiency and functionality of nanostructured materials and devices.

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