With device scaling, the current optical lithography technique is reaching its technological limit to print small features. Extreme Ultra-Violet (EUV) lithography has shown promise to print extremely thin lines reliably and cost-effectively. Many challenges remain before introducing EUV to large scale manufacturing. The main challenge addressed in this study is particle removal from EUV mask surfaces (CrON1, CrON2, and fused silica) and thermal oxide (SiO₂). Effective pre-clean procedures were developed for each surface. As chemical cleaning methods fail to meet SEMATECH criteria, addition of megasonic energy to EUV mask cleaning baths is seen as a promising cleaning methodology. As the requirement to print fine lines needs to be met, all materials used in EUV mask fabrication either absorb the incident EUV wavelength light or reflect it. Therefore, the masks used in the industry will be reflective instead of the conventional transmissive masks. Also, for the same reason, no protective pellicle can be used leading to all the surfaces unprotected from particle contamination. To avoid the detrimental effect of the particle contamination, a cleaning study for nano-particle removal was performed. A dark field microscope was utilized to study the removal of gold nano-particles from surfaces. The cleaning procedures utilized H₂SO₄ and NH₄OH chemistries with and without megasonic irradiation. The cleaning variables were bath concentration, temperature, and megasonic power. The contamination variables were the gold nanoparticles charge and size, from 40nm to 100nm. For 100 nm negatively charged gold nano-particles deposited on a CrON1 surface, a 1:10 H₂SO₄:DI bath at boiling temperature (101°C) without megasonics gave high particle removal efficiency (PRE) values as did a 1:10 H₂SO₄:DI bath at 35°C with 100W megasonics. Comparison of removal of poly diallyl-dimethyl ammonium chloride (PDAC) coated and uncoated gold nano-particles deposited on a CrON1 surface using dilute H₂SO₄ baths indicated that the coated, positively charged nano-particles were more difficult to remove. PRE trends for different baths indicate surface dissolution (shown to be thermodynamically favorable) as the particle removal mechanism. However, experimental etch rates indicated minimal surface etching in a 10 minute bath. Increased surface roughness indicated possible local galvanic corrosion at particle sites. Low surface etching results meet SEMATECH requirements. During the fused silica surface cleaning study, particle charge (negative) and size (100 nm) of the contamination source and cleaning bath chemistry (NH₄OH) were kept constant. Low PREs were obtained at room temperature for all NH₄OH bath concentrations; however, high PREs were obtained at an elevated temperature (78°C) without megasonics and at room temperature in more dilute chemistries with megasonic power applied. Similar PRE trends were demonstrated for thermal SiO₂ surfaces. The experimental etch rates of the thermal SiO₂ agree with published values.

In recent years, polymer-inorganic nanoparticle compositions have been a subject of considerable interest in order to achieve desired chemical, physical properties and mechanical properties. In this study a polymer nanocomposites have been prepared by incorporating silica nanoparticles (~20 nm) as fillers into poly(ethylene oxide) matrix. The composites of poly(ethylene oxide) and silica nanoparticles were prepared by solution blending. The product composites were powders. The thermal properties of the composites were investigated using the Differential Scanning Calorimetry. The Nuclear Magnetic Resonance (13C solid state, T1ρ), Atomic Force Microscopy, X-ray diffraction and Fourier Transform Infrared Spectroscopy were used to investigate the effect of the nanoparticles on the polymer matrix. The results suggest that the silica nanoparticles were reasonably well dispersed in the PEO 35K. The dispersion was accompanied by slightly reduced the crystallinity. However, with increasing the SiO2 nanoparticles the aggregation Phenomenon appears. Moreover, with increase in the MW of the PEO to 100K the dispersion of the nanoparticles decreased and aggregation phenomenon is observed even at lower of SiO2 contents.

Different types of plasmonic nanostructures are proposed and examined experimentally and theoretically, with a view towards sensing applications. First, a self-assembly approach was developed to create arrays of well-ordered glass-supported gold nanoparticles (AuNPs) with controllable particle size and inter-particle spacing. Then, a periodic array of gold nano-disks (AuNDs) supported by a Bragg reflector was proposed and examined in a search for Fano resonances in its optical response. Arrays of heptamer-arranged nanoholes (HNH) in a thin gold film were also proposed and explored theoretically and experimentally, revealing a very rich spectrum of resonances, several exhibiting a Fano lineshape. A commercial implementation of the vectorial finite element method (FEM) was used to model our plasmonic structures. Taking advantage of the periodic nature of the structures, a unit cell containing a single element was modelled. The transmittance, reflectance or absorbance spectra were computed, and the associated electromagnetic fields were obtained by solving the vector wave equations for the electromagnetic field vectors throughout the structures, subject to the applicable boundary conditions, and the applied source fields. The sensing performance of the structures, based on the bulk sensitivity, surface sensitivity and figure of merit (FOM) was calculated. First, a novel bottom-up fabrication approach was applied (by our collaborators) to form a periodic array of AuNPs with controllable size over large areas on SiO2 substrates. In this method, self-assembly of block copolymer micelles loaded with metal precursors was combined with a seeding growth route to create ordered AuNPs of desired size. It was shown that this new fabrication method offers a new approach to tune the AuNP size and edge-to-edge inter-particle spacing while preserving the AuNP ordering. The optical characteristics of the AuNP arrays, such as their size, interparticle spacing, localized surface plasmon resonance (LSPR) wavelength, and bulk sensitivity, were examined, numerically and experimentally. This proposed novel fabrication method is applicable for low-cost mass-production of large-area arrays of high-quality AuNPs on a substrate for sensing applications. Then, we proposed and examined the formation of Fano resonances in a plasmonic-dielectric system consisting of uncoupled gold nano-disk (AuND) arrays on a quarter-wave dielectric stack. The mechanism behind the creation of Fano resonances was explained based on the coherent interference between the reflection of the Bragg stack and the LSPPs of the AuNDs. Fano parameters were obtained by fitting the computational data to the Fano formula. The bulk sensitivities and figure of merit of the Fano resonances were calculated. This plasmonic structure supports Fano resonances with a linewidth around 9 nm which is much narrower than the individual AuND LSPP bandwidth ( 80 nm) and the Bragg stack bandwidth ( 100 nm). Supporting Fano resonances with such a narrow linewidth, the structure has a great potential to be used for sensing applications. Also, this metallic-dielectric nanostructure requires no near-field coupling between AuNDs to generate the Fano resonances. So, the AuNDs can be located far enough from each other to simplify the potential fabrication process. The optical properties of HNH arrays on an SiO2 substrate were investigated, numerically and experimentally. Helium focused ion beam (HeFIB) milling was applied (by Dr. Choloong Hahn) to fabricate well-ordered and well-defined arrays of HNHs. Transmittance spectra of the structures were obtained as the optical response, which exhibits several Fano resonances. Then, the mechanism behind the formation of the Fano resonances was explained, and the sensing performance of the structure was inspected by measuring the bulk sensitivities. This array of nanohole cluster is exciting because it supports propagating SPPs and LSPPs, and also Wood’s anomaly waves, which makes the optical response very rich in excitations and spectral features. Also, as a periodic array of sub-wavelength metallic nanoholes, the system produces extraordinary optical transmission - highly enhanced transmission through (otherwise) opaque metallic films at specific wavelengths, facilitating measurement acquisition in transmission.

Porous materials have garnered significant interest within scientific community mainly because of the possibility of engineering their pores for selective applications. Currently, much research has focused on improving the therapeutic indices of the active pharmaceutical ingredients engineered with nanoparticles. The main goal of this dissertation is to prepare targetable and biodegradable silica/organosilica nanoparticles for biomedical applications with a special focus on engineering particle pores. Herein, the design of biodegradable silica-iron oxide hybrid nanovectors with large mesopores for large protein delivery in cancer cells is described. The mesopores of the nanomaterials span 20 to 60 nm in diameter, and post-functionalization allowed the electrostatic immobilization of large proteins (e.g., mTFP-Ferritin, ~534 kDa). The presence of iron oxide nanophases allowed for the rapid biodegradation of the carrier in fetal bovine serum as well as magnetic responsiveness. The nanovectors released large protein cargos in aqueous solution under acidic pH or magnetic stimuli. The delivery of large proteins was then autonomously achieved in cancer cells via the silica-iron oxide nanovectors, which is thus promising for biomedical applications. Next, the influence of competing noncovalent interactions in the pore walls on the biodegradation of organosilica frameworks for drug delivery applications is studied. Enzymatically-degradable azo-bridged organosilica nanoparticles were prepared and then loaded with the anticancer drug doxorubicin (DOX). Controllable drug release was observed only upon the stimuli-mediated degradation of azo-bridged organosilica nanoparticles in the presence of azoreductase enzyme triggers or under hypoxia conditions. These results demonstrated that azo-bridged organosilica nanoparticles are biocompatible, biodegradable drug carriers and that cell specificity can be achieved both in vitro and in vivo. Overall, the results support the importance of studying self-assembly patterns in hybrid frameworks to better engineer the next generation of dynamic or “soft” porous materials.

Thesis advisor: Baldassare Di Bartolo / Thesis advisor: Pradip Bakshi / The search for multicolored light produced by some IR laser-excited luminescent nano-powders has revealed, for laser power exceeding a threshold value, the emission of white light (WL) with black-body characteristics. I am directing my research to the study of the physical parameters that may influence the threshold power of the laser and the efficiency of the WL emission. A typical compound that I will investigate will consist of nano-powders of SrZrO3 doped with Yb. The parameters of relevance may include Yb concentration, pressure, temperature, size of nano-crystals, exciting power and wavelength of the laser, dynamical parameters such as decay and build-up patterns. The aim of my research will be both theoretical and experimental: theoretical for I will try to uncover the mechanism of the WL production and experimental for the possible application as efficient light sources of systems similar to the ones that I will investigate (oxide nano-powders doped with lanthanide or transition metal ions). The “new” light sources in the market (fluorescence lights sources, and LED lamps) beat the Edison bulbs in efficiency, but they do not produce the black-body emission of the Edison bulbs that is most pleasing to the eye. The search for efficient black-body type of sources is still on and we want to be a part of it. / Thesis (PhD) — Boston College, 2021. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Physics.

A plasma arc erosion process can be used to create metal and metal oxide particles in the ultra-fine size range (<70 µm). An electric arc is struck between two metallic electrodes, submerged in water, melting the surface of the electrodes. When the arc collapses a high energy pressure wave strikes the molten surface of the electrode. When the pressure wave strikes the molten metal, small metallic particles are created from the molten metal and are immediately cooled in the water. Previous research developed a process that used a constant current power supply and electrode motion to create ultra-fine particles. This research improves upon previous research by using a pulsed power supply similar to those used in Electrical Discharge Machining (EDM). The pulsed power supply eliminates the need for electrode motion and improves the rate of particle production, provides control over size of the particles created, and reduces the amount of energy needed to produce the particles. The new process improves the maximum particle production rate from 3.6 g/hr to 14 g/hr, provides a method to control the mean diameter of the particles produced, and reduces the amount of energy needed from 200 kWh/kg(previous constant current process) to 10.6 kWh/kg(using the pulsed power supply).

Kohlenstoffnanoröhren als eigenständige Modifikation des Kohlenstoffs sind zylindrische, aus mehreren Lagen Kohlenstoff aufgebaute Röhren, die über einen Hohlraum im Inneren verfügen. Bereits kurze Zeit nach ihrer Entdeckung, kam die Idee auf, Substanzen in diesen Hohlraum zu füllen. Durch den Einbau von Katalysatormaterial während der Synthese, ist bereits eine Vielzahl von Elementen als Füllmaterial zugänglich. Um jedoch nicht auf Elemente limitiert zu sein, die als Katalysator für die CNT-Synthese dienen, ist es möglich eine postsynthetische Füllung durchzuführen. Hier werden ungefüllte CNT geöffnet und anschließend, unter Ausnutzung der Kapillarkräfte, gefüllt. In der vorliegenden Arbeit wurden zunächst verschiedene Methoden zur Füllung untersucht. Neben lösemittelbasierten Methoden wurde mit Salzschmelzen, durch Gasphasentransport und durch Füllung mit einer kovalenten Präkursorverbindung gefüllt. Da metallische Partikel das Ziel waren, folgte im Anschluss an die Füllung mit Salzen, Salzlösungen, oder anderen Präkursoren jeweils eine Reduktion mit Wasserstoffgas bei erhöhten Temperaturen. Die Ergebnisse der Füllung wurden umfassend mittels Elektronenmikroskopie untersucht. Füllungsgrade wurden mittels Thermogravimetrie bestimmt. So konnten für zahlreiche Elemente eine geeignete Methode zur Füllung mit metallischen Partikeln entwickelt werden. Im Falle der Füllung mit Zinn konnte zudem gezeigt werden, dass ein Zusammenhang zwischen der Dauer der Füllreaktion und dem Anteil an drahtartigen Nanostrukturen in den CNT, sowie ein Zusammenhang zwischen der eingesetzten Lösungskonzentration und dem Füllungsgrad besteht. Im weiteren Verlauf der Arbeit wurde die Synthese von intermetallischen Partikeln in CNT untersucht. Hierbei dienten die Systeme Nickel-Zinn und Cobalt-Zinn, die als vielversprechende Materialien im Einsatz als Anodenmaterial in Lithium-Ionen-Akkumulatoren diskutiert werden, als Modellsysteme. Zunächst wurde gezeigt, dass es nicht möglich ist, aus einem Gemisch des Zinnsalzes und des jeweiligen anderen Salzes erfolgreich intermetallische Partikel herzustellen. Mittels Pulverröntgendiffraktometrie (XRD) und energiedispersiver Röntgenspektroskopie (EDX) konnte gezeigt werden, dass lediglich Zinnpartikel in den CNT vorhanden waren. Schließlich konnte mit dem Verfahren der sequentiellen Füllung eine erfolgreiche Synthese intermetallischer Nanostrukturen bewerkstelligt werden. Hierbei wird die CNT zuerst mit einer Lösung von Zinnchlorid gefüllt und schließlich reduziert. Anschließend erfolgt eine weitere Füllung mit einem Nickel- bzw. Cobaltsalz und einer nachfolgenden Reduktion. Während dieser zweiten Reduktion erfolgt die Bildung der intermetallischen Nanostrukturen in den CNT. Mittels XRD konnte gezeigt werden, dass tatsächlich intermetallische Strukturen in der Probe enthalten sind und dass man zudem durch das Verhältnis der beiden eingesetzten Elemente (Zinn zu Nickel bzw. Cobalt) Einfluss auf die vorherrschende intermetallische Verbindung nehmen kann. Durch EDX-Linienscans und Elementkarten, die am Transmissionselektronenmikroskop angefertigt wurden, konnte nachgewiesen werden, dass einzelne, in den CNT befindliche Partikel, tatsächlich aus den beiden Elementen Zinn und Nickel bzw. Cobalt bestehen und somit intermetallisch sind. Ein erster Test des erhaltenen Materials aus CNT und intermetallischen Nickel-ZinnVerbindungen als Anodenmaterial konnte bereits durchgeführt werden. Die gemessene Kapazität lag bereits im Bereich von Graphit, welches üblicherweise als Anodenmaterial verwendet wird, könnte jedoch durch Erhöhung des Anteils der intermetallischen Verbindung noch weiter gesteigert werden.

Alkaline fuel cells are a promising technology, with their sturdy design and many applications they are held back mostly by their cost. By introducing a catalyst, the activation energy of the cell can be reduced to an overcomable amount. Unfortunately, due to the high cost and sparse availability of the most used catalyst metal today, platinum, it has become apparent that a new suitable catalyst must be found in order to make the fuel cells economically feasible. Silver and palladium have been proposed as promising alternatives, sharing a majority of the traits but with a fraction of the cost. The original aim of this project was to study the performance of electrodes in an alkaline electrolyte loaded with different ratios of palladium and silver. However, due to the COVID-19 situation the project was not able to be completed and the aim of the project changed. The new aim was divided into two parts. The first one being to study how the initial concentration of silver ions affects the size of the obtained particles. This was achieved by a radiolysis-based method of synthesis in an aqueous solution. The second aim was to study the performance of the electrodes loaded with different amounts of silver and different average particle size. However, this part was not possible to conduct either. Therefore, results from a previous study performed by I. L. Soroka et al. was used for discussion. The results point towards a lower initial concentration achieving a smaller average particle size and a lower loading of catalyst on the electrode can be compensated by a smaller average particle size of the catalyst.

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