Focused ion beam (FIB) technique uses a focused beam of ions to scan the surface of aspecimen, analogous to the way scanning electron microscope (SEM) utilizes electrons. Recent developments in the FIB technology have led to beam spot size below 10 nm,which makes FIB suitable for nanofabrication. This project investigated thenanofabrication aspect of the FIB technique, with device applications perspective inseveral directions. Project work included construction of an in-situ FIB electricalmeasurement system and development of its applications, direct measurements ofnanometer scale FIB cuts and fabrication and testing of lateral field emission devices. Research work was performed using a number of materials including Al, Cr, SiO2, Si3N4and their heterostructures. Measurements performed included in-situ resistometricmeasurements, which provided milled depth information by monitoring the resistancechange of a metal track while ion milling it. The reproducibly of this method wasconfirmed by repeating experiments and accuracy was proven by atomic force microscopy(AFM). The system accurately monitored the thickness of 50 nm wide and 400 nm thick(high aspect ratio) Nb tracks while ion milling them. Direct measurements of low aspectratio nanometer scale FIB cuts were performed using AFM on single crystal Si,polycrystalline Nb and an amorphous material. These experiments demonstrated theimportance of materials aspects for example the presence of grains for cuts at this scale. Anew lateral field emission device (in the plane of the chip) was fabricated, as FIB offersseveral advantages for these devices such as control over sharpness and decrease in anodeto-cathode spacing. FIB fabrication achieved field emission tip sharpness below 50 nm andanode-to-cathode spacing below 100 nm. For determining the field emission characteristicsof the devices, a low current (picoampere) measurement system was constructed anddevices operated in ultra high vacuum (10-9 mbar) in picoampere range. One devicefabricated using a FIB sharpening process had a turn on voltage of 57 V.

This thesis investigates the potential of flat optics as a solution to the problem of bulky and expensive optical components in producing lightweight and wearable optoelectronic devices. The research addresses scalability challenges in structure fabrication, design of broadband operating devices, and increasing operational and transmission efficiency in the visible range. It focuses on the experimental part of the challenge. The study evaluates various design approaches, including inverse designs using optimization techniques as well as the use of machine learning algorithms. The thesis aims to explore a path toward high efficiency, wide bandwidth, functional response, and scalable fabrication in flat optics using semiconductor nanostructures. The results demonstrate the potential of using semiconductor nanostructures to engineer efficient, scalable, and broadband optical components in obtain light processing through flat surfaces.

Focused ion beam/scanning electron microscopy (FIB/SEM) is a tool commonly used for applications including preparation of site-specific transmission electron microscopy (TEM) samples, nanotomography, and electronic circuit edit. Another potential application is optical device prototyping; however, the ion beam itself has been shown to cause damage fatal to device operation. This thesis first includes several examples of FIB-fabricated optical devices that had limited functionality compared to simulation. Second, the underlying causes of ion beam-induced optical damage from gallium and xenon ion sources is characterized. Monte Carlo simulations of ion-solid interactions were confirmed using TEM analysis to measure the thickness of the damaged layer. For crystalline samples such as silicon, Raman response can be used as a measure of lattice damage. Using these techniques, it was found that optical damage from a gallium beam is more severe than from a xenon beam, and occurs in the form of lattice amorphization and implantation of beam ions. This damage hinders optical coupling by altering the physical and electronic structure of the sample. Consequently, the xenon PFIB is a better choice for optical device prototyping. / Thesis / Master of Science (MSc) / The second half of the 20th century saw the advent of nanotechnology, both in the context of understanding the structure of the natural world beyond the limit of light microscopy, as well as manipulating materials to create useful microscopic devices, including the computers ubiquitous in today’s life. One technology that has contributed to today’s nano-centric paradigm is the focused ion beam/scanning electron microscope (FIB/SEM). The FIB/SEM is used to machine materials with extreme precision for many diverse applications such as modifying microcircuits, three-dimensional (3D) nanotomography, or to prepare samples for other microscopy techniques. For some applications, however, damage to the sample from the ion beam can be fatal. New ion sources have become available in the past ten years that may cause less damage to samples, and thus open up new applications for FIB. This thesis includes first a description of a series of optical devices prototyped using FIB. This is followed by a comparison of the damage induced by the conventional liquid gallium ion source and new xenon plasma ion sources, and a discussion of the relative merits of the ion sources for optical device fabrication.

Promising strategies for treating diseases and conditions like cancer, tissue necrosis from injury, congenital abnormalities, etc., involve replacing pathologic tissue with healthy tissue. Strategies devoted to the development of tissue to restore, maintain, or improve function is called tissue engineering. Engineering tissue requires three components, cells that can proliferate to form tissue, a microenvironment that nourishes the cells, and a tissue scaffold that provides mechanical stability, controls tissue architecture, and aids in mimicking the cell’s natural extracellular matrix (ECM). Currently, there is much focus on designing scaffolds that recapitulate the topology of cells’ ECM, in vivo, which undoubtedly wields structures with nanoscale dimensions. Although it is widely thought that sub-microscale features in the ECM have the greatest vii impact on cell behavior relative to larger structures, interactions between cells and nanostructures surfaces is not well understood. There have been few comprehensive studies elucidating the effects of both feature dimension and geometry on the initial formation and growth of the axons of individual neurons. Reconnecting the axons of neurons in damaged nerves is vital in restoring function. Understanding how neurons react with nanopatterned surfaces will advance development of optimal biomaterials used for reconnecting neural networks Here, we investigated the effects of micro- and nanostructures of various sizes and shape on neurons at the single cell level. Compulsory to studying interactions between cells and sub-cellular structures is having nanofabrication technologies that enable biomaterials to be patterned at the nanoscale. We also present a novel nanofabrication process, coined Flash Imprint Lithography using a Mask Aligner (FILM), used to pattern nanofeatures in UV-curable biomaterials for tissue engineering applications. Using FILM, we were able to pattern 50 nm lines in polyethylene glycol (PEG). We later used FILM to pattern nanowells in PEG to study the effect of the nanowells on the behavior preadipocytes (PAs). Results of our cell experiments with neurons and PAs suggested that incorporating micro- and nanoscale topography on biomaterial surfaces may enhance biomaterials’ ability to constrain cell development. Moreover, we found the FILM process to be a useful fabrication tool for tissue engineering applications. / text

The possibility to manipulate electromagnetic radiation, as well as mechanical and acoustic waves has been an engaging topic since the beginning of the 20th century. Nowadays, thanks to the progress in technologies and the evolution of fabrication processes, realizing artificial materials that are able to interact with the environment in a desired fashion has become reality. The interest in micro/nanostructured metamaterials involves different field of research, ranging from optics to biology, through optoelectronics and photonics. Unfortunately, realizing experimentally these materials became highly challenging, since the size of the nanostructures are shrinking and the precision of the design became crucial for their effective operation. Disorder is, in fact, an intrinsic characteristic of fabrication processes and harnessing it by turning its unexpected effects in decisive advantages represents one of the ultimate frontiers in research. In this work we combine ab-initio FDTD simulations, fabrication process optimization and experimental results to show that, introducing disorder in metamaterials could constitute a key opportunity to enable many interesting capabilities otherwise locked. This could open up the way to novel applications in several fields, from smart network materials for solar cells and photo-electrochemical devices to all dielectric, highly-tunable structural colors.

Thesis advisor: Michael J. Naughton / Thesis advisor: Michael J. Burns / Recent progress in the study of the brain has been greatly facilitated by the development of new measurement tools capable of minimally-invasive, robust coupling to neuronal assemblies. Two prominent examples are the microelectrode array, which enables electrical signals from large numbers of neurons to be detected and spatiotemporally correlated, and optogenetics, which enables the electrical activity of cells to be controlled with light. In the former case, high spatial density is desirable but, as electrode arrays evolve toward higher density and thus smaller pitch, electrical crosstalk increases. In the latter, finer control over light input is desirable, to enable improved studies of neuroelectronic pathways emanating from specific cell stimulation. Herein, we introduce a coaxial electrode architecture that is uniquely suited to address these issues, as it can simultaneously be utilized as an optical waveguide and a shielded electrode in dense arrays. / Thesis (PhD) — Boston College, 2017. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Physics.

A plasmônica é a área que faz a junção entre fotônica e nanoestruturas. As implicações tecnológicas resultantes do acoplamento entre campos eletromagnéticos e oscilações eletrônicas em um material condutor fazem desta área uma das mais excitantes da óptica atualmente. Neste contexto, o objetivo deste trabalho é o projeto, fabricação e caracterização de nanoestruturas metálicas visando aplicações em óptica difrativa, incluindo filtros e lentes. Inicialmente, uma extensa revisão bibliográfica permitiu definir quais tipos de estruturas seriam abordadas, levando em conta tanto a capacidade computacional para fazer a modelagem numérica quanto a infraestrutura necessária na fabricação dos elementos. A primeira estrutura analisada foi um filtro óptico baseado em ressonância de modo guiado e ressonância plasmônica. Foram projetados e fabricados três filtros operando no azul, verde e vermelho. Resultados experimentais mostraram eficiência acima de 80% e largura de banda em torno de 20 nm, consideravelmente menor que os ~60 nm obtidos previamente na literatura considerando estrutura semelhante. Foi possível verificar as cores puras associadas à ressonância de modo guiado. Além disso, foi demonstrado como gerar as três cores primárias - azul, verde e vermelho - usando apenas o filtro vermelho. A segunda estrutura proposta consiste em uma lente tipo zonas de Fresnel integrada com um filme metálico. Resultados numéricos identificaram uma estrutura ressonante do tipo Fabry-Perot que possibilita uma redução dos lóbulos laterais gerada pela lente por um fator 3.0 na polarização TM e 4.8 na polarização TE. A estrutura foi fabricada usando litografia por nanoimpressão. Por fim, a terceira estrutura analisada foi um holograma binário baseado em metassuperfície, cuja célula básica é composta de um ressoador tipo nanorod. Foi proposta uma geometria na qual a diferença de fase entre os elementos é igual a π independente do comprimento de onda. Assim, o holograma pode operar em uma faixa espectral definida pela largura de banda transmitida. É descrito o inicio da fabricação do elemento usando litografia por feixe de elétrons. / Plasmonics is a field of study that merge photonics and nanostructures. The advanced technological implications makes it one of the most exciting field in Optics in current days. Therefore the objective of this study is the design and fabrication of metallic nanostructures aiming at applications in diffractive optics. Firstly, an extensive literature review allowed to define what types of structures would be addressed, taking into account both software simulations and the require infrastructure for the elements\' fabrication. The first analyzed structure was an optical color filter based on guided mode resonance and surface plasmon resonance. Three filters, operating in blue, green and red, were designed and fabricated using interferometric lithography. Experimental results show above 80% efficiency and ~20 nm bandwidth, which is significantly smaller than ~60 nm previously obtained in the literature with similar structures. It was possible to show the pure colors associated with the modal resonance. Furthermore, it was shown how to obtain the primary red, blue, and green colors using only the red filter. The second structure proposed consists of Fresnel zones plates integrated with a metallic film. Numerical results show a resonant structure which enables side lobe reduction by a factor 3.0 in the TM polarization and 4.8 in the TE polarization. This structure was fabricated using nanoimprint lithography. The third analyzed structure was a binary hologram based on metasurface whose basic cell is composed of a nanorod metallic resonator. The phase difference between two elements is equal to π, regardless of the wavelength; thus, the hologram operates in a spectral band defined by transmitted bandwidth. The first steps of its fabrication process using electron beam lithography are presented and described.

O interesse por aplicações que utilizam efeitos de plásmons poláritons de superfície (SPP) vem crescendo, pois as ondas SPPs apresentam enorme potencial no desenvolvimento de filtros e biossensores ópticos. A sensibilidade da ressonância de plásmons em nanoestruturas permite o estudo em tempo real de variações mínimas em índice de refração, solutos e antígenos. Neste trabalho foram aplicadas técnicas de nanofabricação (litografia por feixe de elétrons e íons) para o desenvolvimento de estruturas plasmônicas e sua posterior caracterização. As estruturas foram utilizadas para verificar propriedades de absorção e fluorescência em moléculas opticamente ativas - Porfirina e Rodamina 6G. As estruturas - conjuntos de fendas e matrizes de buracos circulares com diversos períodos - foram fabricadas em um filme fino de ouro (Au) sobre substrato de vidro (Borofloat 33 - Schott), usando um feixe de íons de Gálio (FEI Quanta Quanta 3D 200i). A transmissão óptica foi estudada na região de 400nm a 900nm (VIS-NIR). Os resultados experimentais foram comparados com simulações computacionais. O estudo da absorção molecular da porfirina foi conduzido observando-se a variação na intensidade da transmissão. Ao alterar a concentração da porfirina sobre as estruturas, foi possível caracterizar a curva de absortividade ε(λ) da porfirina para concentrações entre 100 μg/ml e 500 μg/ml em quantidades mínimas de analito (20 μl). A técnica de microscopia confocal foi empregada no estudo da fluorescência da Rodamina 6G diluída num filme fino de PMMA sobre as estruturas. Ao avaliar a fluorescência da Rodamina 6G na reflexão das estruturas, observou-se o efeito de quenching devido a emissão de plásmons. Os resultados obtidos poderão ser utilizados de apoio a trabalhos futuros, desenvolvidos em plasmônica aplicada a biossensores. / The interest in applications that use the effects of surface plasmon polaritons (SPP) has been increasing. SPPs waves have an enormous potential for the construction of optical filters and biosensors. The sensitivity of plasmon resonance in nano-structures allows studying in real-time minimal variations in the refractive index, solutes and antigens. In this work, we have studied nanofabrication techniques (electron and ion beam lithography) and the characterization of plasmonic structures. Plasmonic effects were used as biosensors of absorption and fluorescence in optically active molecules - Porphyrin and Rhodamine 6G. The structures - sets of slits and arrays of circular holes with different periods - were manufactured in gold (Au) thin film on a glass substrate (Borofloat 33 - Schott) using a galium ion beam equipment (FIB FEI Quanta Quanta 3D 200i). Optical transmission was studied in the region of 400 nm to 900 nm (VIS-NIR). The characterization of structures was realized used the Ocean Optics USB-2000 spectrometer. The experimental results were compared to computer simulations. The study of molecular absorption of porphyrin was conducted by observing the variation in intensity of transmission. By changing the porphyrin concentration in the structures, it was possible to characterize the porphyrin absorptivity curve ε(λ) in concentrations between 100 μg/ml and 500 μg/ml in minimum amounts of analyte (20 μl). Confocal microscopy was used to study the fluorescence of Rhodamine 6G on plasmonic structures. The plasmon quenching effect was observed in the evaluation of the fluorescence of Rhodamine 6G in the reflection of the structures. The results will support future works linking plasmonics and biosensors.

"“One-dimensional” nanostructures like nanotubes and nanorods hold great potential for a wide variety of applications. In particular, one-dimensional nanostructures may be able to provide many significant advantages over traditional spherical particles for drug delivery applications. Recent studies have shown that long, filamentous particles circulate longer within the body than spherical particles, giving them more time to reach the target area and deliver their payload more efficiently. In addition, studies investigating the diffusion of drugs through nanochannels have shown that the drug diffusion profiles can be controlled by varying the nanochannel diameter when the drug diameter and nanochannel diameter are close in size. The combination of increased circulation time and controllable drug release profiles give onedimensional nanostructure great potential for future drug release applications. To fully realize this potential, a simple, low cost, and versatile fabrication method for one-dimensional nanostructures needs to be developed and exploited. The objective of this work is to demonstrate the versatility of template-assisted nanofabrication methods by fabricating a variety of unique protein and polymer one-dimensional nanostructures. This demonstration includes the adaptation of two different template-assisted methods, namely layer-by-layer assembly and template wetting, to fabricate glucose oxidase nanocapsules with both ends sealed, segmented polystyrene and poly(methyl methacrylate) nanorods, and poly(L-lactide)-poly(methyl methacrylate) core-shell nanowires with adjustable shell layer thicknesses. The unique nanostructure morphologies that were achieved using our novel fabrication methods will open the arena for future research focused on process control and optimization for specific applications."

Depuis les années 2000, le développement de la spectroscopie Raman à exaltation de pointe (TERS) a permis l’accès de manière extrêmement localisée aux propriétés structurales et moléculaires à la surface de la matière et à des analyses physico-chimiques combinées. La technologie TERS associe les techniques de microscopie à sonde locale - ici le microscope à force atomique (AFM) - avec le champ proche optique. Elle bénéficie en particulier de la génération, à la surface métaux nobles, de plasmons de surface à l’origine d’exaltation d’ondes électromagnétiques pouvant être confinées dans un volume sub-longueur d'onde à l'extrémité des sondes AFM-TERS. Aujourd'hui le principal verrou technologique en TERS est la conception des sondes AFM en termes de reproductibilité à échelle nanométrique, et de fabrication en série. Ce travail de thèse effectué dans le cadre d’une thèse CIFRE (HORIBA Scientific) a eu pour but de concevoir un nouveau type de sonde AFM-TERS répondant aux exigences de performances et de fabrication actuelles. Pour atteindre cet objectif, une étude de simulation numérique a conduit à proposer une nanostructuration métallique de l’extrémité d’un levier AFM, afin de conduire à une exaltation électromagnétique optimisée. Un procédé de nano- et micro-fabrication a été développé au sein de la plateforme de micro et nano-fabrication de l'IEMN, combinant lithographie électronique et optique, évaporation métallique et gravure sur wafers silicium. Il permet la réalisation en série de sondes AFM dont chaque extrémité est composée d'une nano-antenne métallique de taille sub-longueur d'onde, composée d'un nanodisque supportant un nanocône. La méthode de fabrication proposée permet un contrôle des réponses plasmoniques en termes d’amplification du champ et d’accordabilité de la résonance, qui sont la clé des performances en spectroscopie Raman à exaltation de pointe. Une étude sur l’évaporation inclinée lors du procédé de nano-fabrication développé par lithographie électronique a également été réalisé dans le but de contrôler la forme des nanoparticules – de forme conique à cylindrique avec des parois poreuses -- isolées ou en réseaux denses. Les simulations numériques suggèrent que de tels objets peuvent être des candidats potentiels pour le TERS ou le SERS (spectroscopie Raman à exaltation de surface). / Since the start of the 2000s the evolution of tip-enhanced Raman spectroscopy (TERS) has enabled the simultaneous measurement of localized structural, molecular, and physicochemical properties. TERS technology combines scanning probe microscopy -- atomic force microscopy (AFM) -- with near field optical microscopy. The combined technique is referred to as AFM-TERS. The technique harnesses and exploits the generation of surface plasmons on metal surfaces. These plasmons lead to the generation of confined electromagnetic waves in a sub-wavelength volume at the very tip of the AFM-TERS probe. The main technological challenge today is the design and optimization of an AFM-TERS probe having nanometer-sized dimensions -- and the controlled, reproducible batch fabrication of such structures. The objective of the work presented in this PhD thesis was to design, fabricate, and characterize a new type of AFM probe capable of bettering the current state-of-the-art performances. The PhD was carried out in collaboration with HORIBA and funded partly by a French ‘CIFRE’ grant. In order to meet these objects, comprehensive numerical modelling led to the design of an optimized metal nanostructuring having maximum electromagnetic exaltation -- placed at the extremity of a silicon-based AFM cantilever. A new combined micro and nano fabrication process was developed to achieve this -- to be performed using the existing equipment found in the IEMN cleanroom. The process encompasses techniques such as masking using electron beam (ebeam) lithography and UV photolithography, thermal evaporation of metals and ‘lift-off’ techniques, and highly-controlled dry etching of small silicon mesas structures and deep etching for MEMS cantilever releasing. The process enables the batch-fabrication manufacture of AFM-TERS probes containing matter on the millimeter scale (the silicon probe support), the micrometer scale (the silicon cantilever), and the nanometer scale (the combined metallic disk and cone having sub-wavelength dimensions). This method allows nanostructuring on the optical/plasmonic behavior of TERS probes, the key factor which will lead to higher performance in TERS. Finally, a further study concerning the inclined evaporation of metallic nanostructures via an ebeam-derived lithographic shadow mask was performed in order to control the size and shape of the nanostructuring. The study proved this approach to be feasible. Furthermore, numerical modelling of such structures suggests that they are potential original candidates for both TERS and SERS (surface-enhanced Raman spectroscopy).