Dissertations / Theses on the topic 'Nanospheres Lithography'

Nanotechnology is one of the most innovative and multidisciplinary fields in modern research. Techniques to manipulate and control matter at the nanometric scale, giving the possibility to change the morphology and the physical and chemical properties are growing in number. At the nano scale, changing the morphology implies changing also the properties of matter: many properties are no longer intrinsic but they depend on the size, shape, and even on the environment. One of the most striking example is given by gold and silver colour when they are in the nanoparticle form. Gold, for example ould be vine-red or green, or bluish or black simply by changing the morphology of the particles. Appropriate manipulation of the matter could also give birth at new proprieties such as the transmission of light through holes much smaller that the light wavelength, allowing the possibility to control at a very intimate scale the propagation of light. It is clear that to exploit the great potential of nanotechnology it is important to have nanofabrication techniques that have a very precise control on the production of nanometric materials or materials with nanometric structures. There are many technologies that can produce structures with an outstanding resolution of just a few nanometer (Electron Beam Lithography, Focused Ion Beam). These technologies are ”serial” fabrication tool, they can produce one object at time and this means high costs and low throughput. On the other hand parallel technologies derive from the semiconductor industry and are mostly optical lithographic methods that are limited by the diffraction limit of light (200nm). In this thesis work the need for a nanofabrication tool that can allow the production of smaller nanostructures will be addressed by using a nanofabrication tool that meets the following criteria: • parallel processing • low cost • large area processing (cm2) • scalability • reproducibility • easy implementation We choose to exploit the ability of self aggregation of matter in ordered structures. In particular we exploited the tendency of spherical monodisperse nanoparticles to assemble in ordered, close packed structures known as colloidal crystals. One monolayer of such colloidal crystal is a very interesting structure because it has a well ordered array of pores among the particles that have a well defined size and shape, that could be tuned by simply changing the size of the self assembled colloidal particles. A simple and easy method to create and deposit on different substrate these self assembled monolayer of polystyrene nanoparticles will be presented. Monolayers will be used to synthesize arrays of monodisperse plasmonic nanoparticles with a very good control on their size and shape, allowing the tuning of the plasmonic proprieties on the desired application. We will use the array of plasmonic nanoparticles to realize molecular sensors and to amplify the Raman signal by the Surface Enhanced Raman Scattering effect. We will study the rise in temperature induced by illumination with a laser light resonant with the nanoparticle’s plasmonic transition. This information could be very interesting for the biological application of the nanoparticles arrays since temperature variation in such a very complex environment could have relevant effect. Moreover we will use these 2D colloidal crystal to synthesize different kinds of nanostructures like an array of holes in a metal film. This nanostructure is very interesting since the discovery of its ability to transmit light even if the hole size is much smaller than the light’s wavelength. A synthesis method based on self assembled nanospheres could be useful for the fabrication of such nanostructures because of its high flexibility in changing the nanoparticles size and so the array geometric parameters like hole size and the lattice period. Self assembled monolayers will be used as a template for the synthesis of nanostructured thin films of TiO2. Titania is a semiconductor of great technological interest in many different fields: catalysis, energy conversion, gas sensing. We will fabricate using the same technology two different nanostructured thin film: a macroporous thin films and a surface patterned with a nanobowl pattern. Finally we will demonstrate the use of self assembled monolayers coupled with a standard technology used in the semiconductor industry such the ion implantation. Nanometric patterns will be produced on Si wafers using the ordered monolayer as a mask for the ion beam.
Il campo delle nanotecnologie è uno dei più innovativi e multidisciplinari della ricerca moderna. Sempre pi`u numerose diventano le tecniche per manipolare la materia su scala nanometrica, modificando così le proprietà fisico, chimiche e morfologiche a livelli mai raggiunti prima. Alla nano scala la manipolazione morfologica è accompagnata dal cambiamento delle proprietà che smettono di essere intrinseche della materia ma diventano dipendenti da altri fattori come la forma, la dimensione e l’ambiente in cui le nanostrutture sono immerse. Uno dei casi più eclatanti è il colore dell’oro e dell’argento quando sono sottoforma di particelle nanometriche. L’oro, ad esempio, può essere di colore rosso-vino, verde, blu e nero, semplicemente cambiando la forma o l’ambiente attorno ad esso. Manipolando la materia opportunamente possono comparire nuove proprietà come la trasmissione della luce attraverso aperture che sono molto più piccole della lunghezza d’onda della luce, dando la possibilità di ottenere il controllo della propagazione della luce ad un livello molto intimo. Si può capire quindi come per poter sfruttare le enormi potenzialità offerte dalle nanotecnologie sia importante avere tecnologie di fabbricazione che permettano un preciso controllo nella produzione di oggetti nanometrici o con strutture nanometriche. Le tecnologie al momento disponibili che permettono di creare strutture con precisione molto elevata (pochi nanometri) sono tecnologie ”seriali” come l’Electron Beam Lithography o il Focused Ion Beam. Queste tecniche sono limitate alla produzione di un oggetto alla volta e quindi comportano costi elevati e lunghi tempi. Le tecnologie ”parallele” derivano dall’industria dei semiconduttori e sono tecniche litografiche che hanno come limite la risoluzione della luce utilizzata ( 200nm). In questo lavoro di tesi si cercherà di dare risposta alla domanda di tecniche di fabbricazione di strutture nanometriche utilizzando una tecnica che abbia le seguenti caratteristiche: • quickness • low cost • ability to synthesize very small nanostructures • reproducibility • easy implementation Si è scelto di utilizzare la capacità della materia di organizzarsi spontaneamente in strutture ordinate. In particolare si è sfruttata la tendenza di nanoparticelle sferiche di polistirene ad impaccarsi in strutture compatte ed ordinate costituendo dei ”cristalli colloidali”. Un singolo strato di nanosfere autoassemblate è una struttura interessante perchè presenta dei pori tra le particelle di forma e dimensioni ben definite, che possono essere modificate cambiando le dimensioni delle sfere che costituiscono il cristallo bidimensionale. Verrà illustrato un metodo semplice e rapido per ottenere questi monostrati di particelle ordinate e per poterli depositare su vari substrati. Questi cristalli bidimensionali verranno utilizzati per depositare una matrice ordinata di nanoparticelle plasmoniche, con un ottimo controllo sulla loro forma e dimensioni, consentendo di realizzare particelle con proprietà su misura per l’applicazione desiderata. Verranno anche studiate applicazioni di queste nanoparticelle come sensori di molecole e per amplificare il segnale Raman grazie all’effetto SERS. Verrà inoltre studiato l’aumento di temperatura di queste nanoparticelle quando vengono illuminate da un laser risonante con la loro risonanza di plasma di superficie. Per applicazioni spettroscopiche applicate a sistemi biologici il cambiamento di temperatura può avere effetti rilevanti in un ambiente complesso come quello biologico. In seguito verrà dimostrato come questi cristalli colloidali bidimensionali possono essere utilizzati per creare altre classi di nanostrutture, come ad esempio una matrice di buchi nanometrici in un film metallico. Queste strutture sono studiate da quando è stato scoperta la loro capacità di far trasmettere attraverso strutture che sono molto minori del limite di diffrazione per le lunghezze d’onda trasmesse. Una sintesi che si basa sulle nanosfere autoassemblate può essere interessante per queste strutture grazie alla sua intrinseca flessibilità. Si possono infatti cambiare in modo molto semplice i parametri geometrici che caratterizzano la matrice di buchi quali le dimensioni dei buchi e il periodo degli stessi. Un’altra tipologia di nanostrutture che verrà realizzata sono film sottili nanostrutturati di TiO2. La titania è un semiconduttore di grande interesse tecnologico in molti campi diversi: dalla catalisi, alla conversione di energia ai sensori di gas. Verranno fabbricati, con la stessa tecnologia, dei film con una porosità ordinata e delle superfici nanostrutturate con un motivo a incavi. Infine verrà dimostrata la possibilità di utilizzare i cristalli colloidali 2D accoppiati con una tecnologia molto utilizzata dall’industria dei semiconduttori quale l’impiantatore ionico. Pattern nanometrici verranno realizzati su silicio utilizzando le nanoparticelle autoassemblate come maschera per il fascio ionico.

A novel localized surface plasmon resonance (LSPR) sensor that differentiates between background refractive index changes and surface-binding of a target analyte (e.g. a target molecule, protein, or bacterium) is presented. Standard, single channel LSPR sensors cannot differentiate these two effects as their design allows only one mode to be coupled. This novel technique uses two surface plasmon modes to simultaneously measure surface binding and solution refractive index changes. This increases the sensitivity of the sensor. Different channels or modes can be created in sensors with the introduction of gold nanospheres or gold nanorods that act as receptor mechanisms. Once immobilization was achieved on gold nanospheres, the technique was optimized to achieve the same immobilization for gold nanorods to get the expected dual mode spectrum. Intricate fabrication methods are illustrated with using chemically terminated self assembled monolayers. Then the fabrication process advances from chemically silanized nanoparticles, on to specific and systematic patterns generated with the use of Electron Beam Lithography. Comparisons are made within the different methods used, and guidelines are set to create possible room for improvement. Some methods implemented failed, but there was a lot to learn from these unsuccessful outcomes. Finally, the applications of the dual mode sensor are introduced, and current venues where the sensors can be used in chemical and biological settings are discussed.

Thesis advisor: Zhifeng Ren
Thesis advisor: Krzysztof Kempa
Many different techniques are available to create nanopatterns in nanoscale devices. However, a few are flexible and inexpensive enough to be practical in the nanotechnology. Here, we study the nanosphere lithography (NSL) based on a self-assembly of microspheres. Using this technique, we have developed various patterns in metallic films, ranging from honeycomb arrays of "quasi-triangles" to circular holes. These various patterns have been used subsequently either as nano-optical structures directly, with remarkable optical and plasmonic properties, or as substrates for further nano-processing. In one such nano-processing, the "quasi-triangle" patterns were used as a catalyst for carbon nanotube growth. The resulting aligned arrays of carbon nanotubes were employed in nanocoax solar cells. In another nano-processing, the arrays were used as masks for electrodeposition. In addition to the nano processing and measurements, we have employed the FDTD computer simulations, to develop a full understanding of the nano-optical and plasmonic properties of the developed structures
Thesis (PhD) — Boston College, 2011
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Physics

Magnetic nanostructures have widespread applications in many areas of physics and engineering, and nanosphere lithography has recently emerged as promising tool for the fabrication of such nanostructures. The goal of this research is to explore the magnetic properties of a thin film of ferromagnetic material deposited onto a hexagonally close-packed monolayer array of polystyrene nanospheres, and how they differ from the magnetic properties of a typical flat thin film. The first portion of this research focuses on determining the optimum conditions for depositing a monolayer of nanospheres onto chemically pretreated silicon substrates (via drop-coating) and the subsequent characterization of the deposited nanosphere layer with scanning electron microscopy. Single layers of permalloy (Ni80Fe20) are then deposited on top of the nanosphere array via DC magnetron sputtering, resulting in a thin film array of magnetic nanocaps. The coercivities of the thin films are measured using a home-built magneto-optical Kerr effect (MOKE) system in longitudinal arrangement. MOKE measurements show that for a single layer of permalloy (Py), the coercivity of a thin film deposited onto an array of nanospheres increases compared to that of a flat thin film. In addition, the coercivity increases as the nanosphere size decreases for the same deposited layer. It is postulated that magnetic exchange decoupling between neighboring nanocaps suppresses the propagation of magnetic domain walls, and this pinning of the domain walls is thought to be the primary source of the increase in coercivity.

This dissertation focuses on four research topics: self-assembly of colloidal nanoparticles, surface modifications of the properties of ionically self-assembled multilayer films, surface enhanced Raman spectroscopy of functionalized gold nanoparticles, and two photon uncaging in gel. Those techniques are used for development of novel nanofabrication methods for top-down and bottom-up assembly of nanostructures, by modifying the properties of nanopatterned surfaces with photoactive ligands, and other technologies. First I describe the development of an improved method for nanosphere lithography, a variation of the convective self-assembly technique. The method exhibited high reproducibility and yielded high quality monolayer crystals by withdrawing a meniscus of liquid polystyrene spheres solution and subsequent evaporation of the solvent. The monolayer crystal was used as an evaporation mask to create surface arrays of gold nanotriangular particles. Metal nanoparticles, with sharp features or narrow gaps, exhibit strong plasmonic properties. I took advantage of those properties to attempt to create patchy modifications of the surface functionalization of gold nanotriangular particles treated with photosensitive molecules. Two molecules denoted, P3-DTC, and LIP3, were used as functional molecules attached to the gold nanoparticles. After interaction with 356nm UV light, part of those molecules cleaves off the surface of the nanoparticles rendering the surface modified with a new functional group. The modification takes place only at the plasmonic hot spots of those nanoparticles, resulting in a patchy modification of the properties of the nanoparticles. I built polymer Ionically Self-assembled Multilayer (ISAM) films using a Layer-by-Layer deposition technique and treated them to alter their surface adhesion properties. Poly (allylamine hydrochloride) (PAH), and poly (styrene sulfonate) (PSS) are a very well-studied system of polyelectrolytes for LbL deposition. ISAM films built from those polyelectrolytes are rich in amine groups to which nanoparticles, cells, tissue cultures, ligands can be made to adhere. In my work I developed a method for selective modification of the surface adhesiveness, by neutralizing the amine groups trough acetylation with acetic anhydride. With resolution from a few microns to a few hundred nanometers, I selectively passivated some areas of the ISAM film while others I left unaltered. I tested the effect of the acetic anhydride passivation by performing Horse Radish Peroxidase (HRP) test which quantifies the amount of free amines on the surface of the film. I also demonstrated the patchy modification of surface adhesiveness by introducing gold nanospheres which attached only to the amine active areas of the modified ISAM film. Photoactivatable fluorophores, i.e. compounds and other entities that may transform into a fluorescent form on absorption of a photon can be employed in multidimetional volume patterning. I studied the photoactivation of aryl azides in gelatin matrix. Specifically, I used Azidocoumarin 151 as a test molecule to undergo two-photon activation, and then measured the resulting photoluminescence. The activation of the Azidocoumarin 151 can be used to create arbitrary 3D patterns of modified functionality inside the gel. The activated molecules can be used as sites for further modification of the patterning inside the volume of the gel. Possible modifications include attaching biomolecules, nanoparticles, or individual cells. Acknowledgements I would like to acknowledge my adviser Hans Robinson for giving me the opportunity to work on several very interesting projects. Dr. Robinson has thought me critical thinking and supported greatly my research in his laboratory. He was always kind and willing to discuss scientific ideas and therefore contributed to my development as a successful graduate student. Iâ d like to also thank Dr. Richie Davis and Dr. Webster Santons for the useful discussions about my projects. I had the great pleasure to work closely with several graduate students during my time at Virginia Tech. Kai Chen, helped me get into the field of polymer self assembled films. I worked closely with Jason Ridley on modifying surface properties of ISAM films. Brandon Thorpe has been a constant supplier of a variety of compounds that I used in my SERS studies. Iâ d like to thank my fellow graduate students from Dr. Robinsonâ s group, Chih-Yu Jao, Eric See, Kirby Mayers, for being great company and lending help when I need it. During my stay at Virginia Tech I have met some wonderful faculty and staff at the Department of Physics. They were all very helpful, but Iâ d like to extend special thanks to Chris Thomas, Dr. Ghiti Khodaparast, Dr. Mark Pitt, Dr. Tetsuro Mizutani, and Randy Heflin. Finally, Iâ d like to thank my wife Elitsa for being patient during my time as a graduate student. Iâ d like to also thank my daughter Eleonora and son Alexander for being the cutest kids in the world and for cheering me up all the time.
Ph. D.

The use of plasmonic nanostructures in sensing applications has increased in recent years owing to improved fabrication methods. Reports in the literature have highlighted the great potential of film-over nanosphere (FON) and nanotriangle surfaces as sensitive and reproducible Surface-Enhanced Raman Scattering (SERS) substrates. The relationship between the physical and optical properties of nanostructured arrays is of great importance and it has a significant influence on the SERS enhancement exhibited by the arrays. However, there has been no comparative study on the plasmonic and Raman properties of closely related FON and nanotriangle substrates. This research details a systematic investigation into the origin of SERS enhancement in a series of nanostructures fabricated via modified nanosphere lithography (NSL). The symbiotic relationship between SERS and plasmonics was exploited by using SERS to probe and evaluate the nanostructured plasmonic surfaces. The relationship between the physical and optical properties of the nanostructures was investigated to understand and determine the optimal structures for use in SERS analysis. The optimal substrates identified for every series investigated were not FON or nanotriangle arrays but instead the closely related film-over etched nanosphere (FOEN) and nanohole arrays which were the result of an etching step in the fabrication process. The transition between nanotriangle and nanohole was studied and the localisation of hot-spots on the structures was identified. Experimental SERS false-colour images showed that in nanotriangle arrays, the electric field was concentrated at the point at which two triangle apexes met. In nanohole arrays, the electric field was greatest on the metal lattice that surrounds the holes. As the diameter of the nanoholes decreased, the electric field was located around the rim of the holes and in nanohole arrays with very small diameters the electric field was concentrated in the centre of the hole. The experimental results were in good agreement with theoretical predications. Nanohole arrays that were shown to have high SERS activity were used in a proof-of-concept SERS sensing study resulting in the detection of labelled Streptavidin at nanomolar concentrations. This method was then applied to a real-life system to probe the interaction of Aurora A with IKKβ peptides.

In this work, fabrication and characterisation of nanostructure devices has been performed on InGaN/GaN multiple quantum wells (MQW) grown on either c-plane sapphire or (111) silicon substrates. A cost effective nanosphere lithography technique has been employed for the fabrication of a number of nano structures such as nanorod arrays, nanoholes arrays; and single micro-disk lasers. Photonic crystal structures based on nanohole arrays have been designed and then fabricated on InGaN/GaN MQWs with an emission wavelength of 500 nm grown on c-plane sapphire by means of a nanosphere lithography technique, demonstrating a clear photonic crystal effect. Significant suppression of spontaneous emission has been observed when the emission is within the photonic bandgap. Angular dependent measurements show a change in the far-field pattern when the emission lies outside the photonic bandgap compared with the emission which lies inside the photonic bandgap. A coherent nanocavity a two-dimensional (2D) periodic array of nanodisks, was designed and fabricated on an InGaN/GaN MQW structure with an emission wavelength at 510 nm, leading to a significant enhancement in the internal quantum efficiency (IQE) as a result of enhanced spontaneous emission rate. Finite-difference time-domain (FDTD) analysis has performed for the structure design. The coherent nanocavity effect has been confirmed using means of time-resolved photoluminescence measurements, showing a clear enhancement in spontaneous emission rate. Finally, an improvement in IQE of 88 times at 510 nm has been achieved. Optically pumped green lasing has been achieved with thresholds as low as 1 kW/cm2, using an InGaN/GaN based micro-disk with an undercut structure on silicon substrates. The micro-disks with a diameter of around 1 μm were fabricated by means of a combination of a cost-effective silica micro-sphere approach, dry-etching and subsequent a wet-etching. The combination of these techniques both minimises the roughness of the sidewalls of the micro-disks and also produces excellent circular geometry. Utilizing this fabrication process, lasing has been achieved at room temperature under optical pumping from a continuous-wave laser diode. Time–resolved micro-photoluminescence (PL) and confocal PL measurements have been performed in order to further confirm the lasing action in whispering gallery modes and also investigate the excitonic recombination dynamics of the lasing.

In this study, template-based methods are used for the fabrication of various nanostructures such as nandots, nanorods, nanowires, nanotubes, and core-shell structures. Porous alumina membranes were employed as templates and metal nanostructures were synthesized in the templates by electrodeposition. By using lithography techniques, controlled patterned nanostructures were also fabricated on alumina templates. The magnetic properties of the various metal nanostructures were investigated. The pore size, interpore distance, and pore geometry highly affect magnetic properties of nanostructures grown in the templates. Hexagonally ordered porous alumina templates can be fabricated by two-step anodization. The pore diameters and interpore distances were readily controlled by appropriately changing anodization conditions and pore widening time. Alumina templates with various pore geometries were also successfully synthesized by changing applied voltage, increasing and decreasing, during a third anodization step. To understand magnetic properties of nanostructures with different aspect rations in the form of nanodots, nanorods, or nanowires, Fe nanostructures were fabricated in the templates by controlling of electrodeposition times. The coercivity of nanostructures increased with increasing aspect ratio. The anisotropy of the arrays was governed by the shape anisotropy of the magnetic objects with different aspect ratios. nanowires in mild-hard alumina and conventional alumina templates showed distinct differences in the squareness of hysteresis loops and coercivity both as a function of pore structure and magnetic component. Iron oxide nanotubes with a unique inner-surface were also fabricated by an electrodeposition method. β-FeOOH nanotubes were grown in alumina templates and transformed into hematite and magnetite structures during various heating processes. Hematite nanotubes are composed of small nanoparticles less than 20 nm diameters and the hysteresis loops and FC-ZFC curves show superparamagnetic properties without the Morin transition. In the case of magnetite nanotubes, which consist of slightly larger nanoparticles, hysteresis loops show ferromagnetism with weak coercivity at room temperature while FC-ZFC curves exhibit the Verwey transition at 125 K. For the patterning of nanowires, lithography techniques including nanosphere lithography and e-beam lithography were used. Nanosphere lithography used self-assembled PS spheres as a mask creates holes between spheres and the size of the holes is determined by the size and geometry of ordered PS spheres on the templates. This method can grow patterned nanowires arrays and also produce unique cup-shaped nanostructures with sizes ranging from micrometer down to several nanometers. E-beam lithography was also combined with template-based electrodeposition. Of these two lithographic methods, this one is the most powerful in the fabrication of patterned nanostructures with high aspect ratios. Various features and the sizes of patterned structures can be readily controlled. By the directing the pore diameters and interpore distances of the alumina template, the size and number of patterned nanowires are also adjustable.

Recent advances in nanotechnology and the biotechnology revolution have created an immense opportunity for the use of noble metal nanoparticles as Surface Enhanced Raman Spectroscopy (SERS) substrates for biological sensing and diagnostics. This is because SERS enhances the intensity of the Raman scattered signal from an analyte by orders of 106 or more. This dissertation deals with the different aspects involved in the application of SERS for biosensing. It discusses initial studies performed using traditional chemically reduced silver colloidal nanoparticles for the SERS detection of a myriad of proteins and nucleic acids. It examines ways to circumvent the inherent aggregation problems associated with colloidal nanoparticles that frequently lead to poor data reproducibility. The different methods examined to create robust SERS substrates include the creation of thermally evaporated silver island films on microscope glass slides, using the technique of Nanosphere Lithography (NSL) to create hexagonally close packed periodic particle arrays of silver nanoparticles on glass substrates as well as the use of optically tunable gold nanoshell films on glass substrates. The three different types of SERS surfaces are characterized using UV-Vis absorption spectroscopy, Electron Microscopy (EM), Atomic Force Microscopy (AFM) as well as SERS using the model Raman active molecule trans-1,2-bis(4-pyridyl)ethylene (BPE). Also discussed is ongoing work in the initial stages of the development of a SERS based biosensor using gold nanoshell films for the direct detection of b-amyloid, the causative agent for Alzheimer's disease. Lastly, the use of gold nanoshells as SERS substrates for the intracellular detection of various biomolecules within mouse fibroblast cells in cell culture is discussed. The dissertation puts into perspective how this study can represent the first steps in the development of a robust gold nanoshell based SERS biosensor that can improve the ability to monitor biological processes in real time, thus providing new avenues for designing systems for the early diagnosis of diseases.

Incorporation of silver nanoparticles (AgNPs) into an increasing number of consumer products has led to concern over the potential ecological impacts of their unintended release to the environment. Dissolution is an important environmental transformation that affects the form and concentration of AgNPs in natural waters; however, studies on AgNP dissolution kinetics are complicated by nanoparticle aggregation. Herein, nanosphere lithography (NSL) was used to fabricate uniform arrays of AgNPs immobilized on glass substrates. Nanoparticle immobilization enabled controlled evaluation of AgNP dissolution in an air-saturated phosphate buffer (pH 7, 25 °C) under variable NaCl concentrations in the absence of aggregation. Atomic force microscopy (AFM) was used to monitor changes in particle morphology and dissolution. Over the first day of exposure to ⠥10 mM NaCl, the in-plane AgNP shape changed from triangular to circular, the sidewalls steepened, and the height increased by 6-12 nm. Subsequently, particle height and in-plane radius decreased at a constant rate over a 2-week period. Dissolution rates varied linearly from 0.4 to 2.2 nm/d over the 10-550 mM NaCl concentration range tested. NaCl-catalyzed dissolution of AgNPs may play an important role in AgNP fate in saline waters and biological media. This study demonstrates the utility of NSL and AFM for the direct investigation of un-aggregated AgNP dissolution.
Master of Science

The environmental fate and transport of engineered nanomaterials have been broadly investigated and evaluated in many published studies. Silver nanoparticles (AgNPs) represent one of the most widely manufactured nanomaterials. They are currently being incorporated into a wide range of consumer products due to their purported antimicrobial properties. However, either the AgNPs themselves or dissolved Ag+ ions has a significant potential for the environmental release. The safety issues for nanoparticles are continuously being tested because of their potential danger to the environment and human health. Studies have explored the toxicity of AgNPs to a variety of organisms and have shown such toxicity is primarily driven by Ag+ ion release. Dissolution of nanoparticles is an important process that alters their properties and is a critical step in determining their safety. Therefore, studying nanoparticles' dissolution can help in the current move towards safer design and application of nanoparticles. This research endeavor sought to acquire comprehensive kinetic data of AgNP dissolution to aid in the development of quantitative risk assessments of AgNP fate. To evaluate the dissolution process in the absence of nanoparticle aggregation, AgNP arrays were produced on glass substrates using nanosphere lithography (NSL). Changes in the size and shape of the prepared AgNP arrays were monitored during the dissolution process by atomic force microscopy (AFM). The dissolution of AgNP is affected by both internal and external factors. First, surface coating effects were investigated by using three different coating agents (BSA, PEG1000, and PEG5000). Capping agent effects nanoparticle transformation rate by blocking reactants from the nanoparticle surface. Coatings prevented dissolution to different extents due to the various way they were attached to the AgNP surface. Evidence for the existence of bonds between the coating agents and the AgNPs was obtained by surface enhanced Raman spectroscopy. Moreover, to study the size effects on AgNP dissolution, small, medium, and large sized AgNPs were used. The surrounding medium and temperature were the two variables that were included in the size effects study. Relationships were established between medium concentration and dissolution rate for three different sized AgNP samples. By using the Arrhenius equation to plot the reaction constant vs. reaction temperature, the activation energy of AgNPs of different sizes were obtained and compared.
Doctor of Philosophy
Nanomaterials, defined as materials with at least one characteristic dimension less than 100 nm, often have useful attributes that are distinct from the bulk material. The novel physical, chemical, and biological properties enable the promising applications in various manufacturing industry. Silver nanoparticles (AgNPs) represent one of the most widely manufactured nanomaterials and has been used as the antimicrobial agent in a wide range of consumer products. However, either the AgNPs themselves or dissolved Ag+ ions has a significant potential for the environmental release. The environmental fate and transport of AgNPs drawn considerable attentions because of the potential danger to environment and human health. Dissolution of nanoparticles is an important process that alters their properties and is a critical step in determining their safety. Ag+ ions migrate from the nanoparticle surface to the bulk solution when an AgNP dissolves. Studying nanoparticles' dissolution can help in the current move towards safer design and application of nanoparticles. This research aimed to acquire comprehensive kinetic data of AgNP dissolution to aid in the development of quantitative risk assessments of AgNP fate. AgNP arrays were produced on glass substrates using nanosphere lithography (NSL) and changes in the size and shape during the dissolution process were monitored by atomic force microscopy (AFM). First, surface coating effects were investigated by using three different coating agents. Coatings prevented dissolution to different extents due to the various way they were attached to the AgNP surface. Moreover, small, medium, and large sized AgNPs were used to study the size effects on AgNP dissolution. The surrounding medium concentration and temperature were the two variables that were included in the size effects study.

Metal-based nanoparticles (MNPs) are becoming increasingly common in commercial products. Release of these materials into the environment raises concerns about the potential risks they pose to aquatic life. Predicting these risks requires an understanding of MNPs' chemical transformations. In this study, arrays of immobilized MNPs fabricated by nanosphere lithography (NSL) were used to investigate environmental transformations of MNPs. Specifically, sulfidation of silver nanoparticles (Ag NPs) and dissolution of copper-based nanoparticles (Cu NPs) were investigated. Atomic force microscopy (AFM) and transmission electron microscopy were the primary analytical techniques for these investigations. Because the MNPs were immobilized on a solid surface, the samples were field deployable, environmentally relevant metal concentrations were maintained, and the confounding influence of MNP aggregation was eliminated. Ag NP samples were deployed in a full-scale wastewater treatment plant. Sulfidation occurred almost exclusively in anaerobic zones of the WWTP, where the initial sulfidation rate was 11-14 nm of Ag converted to Ag2S per day. Conversion to Ag2S was complete within 7-10 d. Dissolution rates of Cu-based NPs were measured in situ over a range of pH by flow-cell AFM. Based on the measured rates, CuO/Cu(OH)2 NPs dissolve completely within a matter of hours at any pH, metallic Cu NPs persist for a few hours to days, and CuxS NPs do not dissolve significantly over the time scales studied. Field deployment of samples in a freshwater stream confirmed these conclusions for a natural aquatic system. This research demonstrates that environmental transformations of MNPs will be a key factor in determining the ultimate form and concentration of NPs that aquatic organisms will be exposed to.
Ph. D.

Metal oxide nanostructures characterized by multiple morphologies and structures are at the forefront of applications driven nanotechnology research. In particular, they represent a versatile solution for performance enhancement and applications in multifunctional devices and offer distinct advantages over their bulk counterparts. The current state in ZnO nanomaterials research and its impact in nanotechnology and modern engineering are discussed through the lens of con-tinuing technological advances in synthetic techniques allowing to obtain the material with predefined specific set of criteria including size, functionality, and uniqueness. Aim of this research activity is fabrication and study of the potential ap-plications as biomolecular nanoplatforms of ZnO nanostructures obtained using different synthetic techniques ranging from vapor phase deposition (Metal-Organic Chemical Vapor Deposition) to solution growth (Chemical Bath Depo-sition). Moreover, hybrid synthetic approaches are used to obtain complex hier-archical ZnO structures having dual or multiple morphologies. The non-covalent interaction of these inorganic nanosystems with organic molecules, having spe-cific chemical behavior, represents a strategy to obtain hybrid organic-inorganic nanomaterials, thus offering interesting potentiality for the design of high per-formance devices. In particular, it is demonstrated that integration of Metal-Organic Chemical Vapor Deposition and Chemical Bath Deposition strategies with Nanosphere Colloidal Lithography allows to define two-dimensional hybrid ZnO-SiO2 nanoarrays having great potential as innovative fluorescence sensing substrates with individual addressability and tuning of the biomolecular detec-tion capability. Combination of Metal-Organic Chemical Vapor Deposition with Electro-spinning leads to fabrication of core shell Zn-doped TiO2 ZnO nanofibers char-acterised by hierarchical growth of ZnO nanoneedles onto the TiO2 nanofiber surface. XRD measurements revealed that after ZnO deposition at T > 500 °C, the TiO2 nanofibers were composed of the anatase rutile mixed phases with dif-ferent fractions of rutile, modulated by the Zn dopant concentration. These com-posite nanomaterials may be intriguing to the future study of nanofiber photo-catalysts and sensors, and functional properties based on titanium dioxide.

Carbon nanotubes (CNTs) have become one of the most interesting allotropes of carbon due to their intriguing mechanical, electrical, thermal and optical properties. The synthesis and electron emission properties of CNT arrays have been investigated in this work. Vertically aligned CNTs of different densities were synthesized on copper substrate with catalyst dots patterned by nanosphere lithography. The CNTs synthesized with catalyst dots patterned by spheres of 500 nm diameter exhibited the best electron emission properties with the lowest turn-on/threshold electric fields and the highest field enhancement factor. Furthermore, CNTs were treated with NH3 plasma for various durations and the optimum enhancement was obtained for a plasma treatment of 1.0 min. CNT point emitters were also synthesized on a flat-tip or a sharp-tip to understand the effect of emitter geometry on the electron emission. The experimental results show that electron emission can be enhanced by decreasing the screening effect of the electric field by neighboring CNTs. In another part of the dissertation, vertically aligned CNTs were synthesized on stainless steel (SS) substrates with and without chemical etching or catalyst deposition. The density and length of CNTs were determined by synthesis time. For a prolonged growth time, the catalyst activity terminated and the plasma started etching CNTs destructively. CNTs with uniform diameter and length were synthesized on SS substrates subjected to chemical etching for a period of 40 minutes before the growth. The direct contact of CNTs with stainless steel allowed for the better field emission performance of CNTs synthesized on pristine SS as compared to the CNTs synthesized on Ni/Cr coated SS. Finally, fabrication of large arrays of free-standing vertically aligned CNT/SnO2 core-shell structures was explored by using a simple wet-chemical route. The structure of the SnO2 nanoparticles was studied by X-ray diffraction and electron microscopy. Transmission electron microscopy reveals that a uniform layer of SnO2 is conformally coated on every tapered CNT. The strong adhesion of CNTs with SS guaranteed the formation of the core-shell structures of CNTs with SnO2 or other metal oxides, which are expected to have applications in chemical sensors and lithium ion batteries.

Cluster-assembled nanostructured Titanium Oxide (ns-TiOx) deposited by Supersonic Cluster Beam Deposition (SCBD) recently proved to be a very promising biomaterial. The intrinsic nanostructure of this material, with fine granularity, high porosity and specific area, coupled to the chemical reactivity of the surface is likely to be a key element in determining the biological affinity of the material with nanometer-sized biomolecules, such as proteins. However, little is known of the specific role played by each of these surface properties in the interaction of proteins with nanostructured biocompatible materials. For understanding the role of different surface properties we used atomic force microscopy (AFM) to study morpho-chemical nature of ns-TiOx biocompatible surfaces. AFM Force-Spectroscopy measurements have been used to characterize local adhesive properties of ns-TiOx surfaces. In order to achieve this goal we have developed a patterning strategy based on the combined use of SCBD and Nanosphere Lithography (NSL), for the production of sub-micrometer patterns of ns-TiOx on glass and other substrates. With this methodology one can have both target and reference material in the same investigation area. Results indicated that atoms on the surface of ns-TiOx can form coordinate bond with protein molecules thereby aiding in irreversible protein adsorption at the same time retaining complete biological activity. To further understand how protein adsorption is affected by the buffer medium and by the surface properties of the substrate, we have measured the point of zero charge (PZC) of nanostructured cluster-assembled TiOx. As each kind of protein has different isoelectric point (IEP), hence their adsorption is greatly affected by pH of the buffering medium and concentrations of ions in the solutions. To this purpose, colloidal probes were developed to measure attractive and repulsive forces of a silica micro-sphere against metal oxide surface as a function of pH. Estimated PZC values for TiOx (rutile) and ns-TiOx is 4.9 ± 0.5 & 3.0 ± 0.5, the latter being significantly smaller than PZC typically measured on crystalline surfaces. These results can open up new avenues towards understanding adsorption characteristics of various proteins on metal oxide surfaces.

Cette thèse est consacrée à la transmission optique extraordinaire observée dans systèmes diffractifs. EOT est perspective pour des applications plasmoniques en raison de l’amélioration du rapport signal / bruit et pour la conception simplifiée de l’appareil. Visant des matériaux disponibles et des méthodes de nanotexturation compatibles avec l’industrie, une étude systématique de l’EOT à travers des films d’aluminium a été réalisée. D’abord, une modification de la lithographie interférentielle permettant la fabrication rapide de réseaux à profondeur variable a été proposée, théoriquement établie et validée expérimentalement. En utilisant cette approche, l’existence d’une profondeur de réseau optimale pour l’EOT a été démontrée expérimentalement et la structure résolue en profondeur a induit des changements de couleurs observés en transmission. Pour la première fois, l’effet de l’EOT a été démontré expérimentalement dans des échantillons polycristallins, fabriqués par nano-photolithographie colloïdale. La présence de désordre sub-longueur d’onde dans la disposition des nanopores affecte fortement l’efficacité de l’EOT, qui a été étudiée à la fois expérimentalement et numériquement. Un modèle phénoménologique d’EOT dans les structures polycristallines et un coefficient de désordre sans dimension sont proposés afin d’expliquer les courbes de transmission mesurées. La dépendance entre la profondeur du réseau et le désordre a été étudiée numériquement. L’étude systématique de l’EOT dans divers systèmes de diffraction présentés dans cette thèse pourrait ouvrir la voie à des dispositifs plasmoniques plus efficaces et à des applications industrielles
The thesis is devoted to the Extraordinary Optical Transmission observed in diffractive systems. An industrial need in integration and miniaturization of optical components stimulates the development of planar grating-based devices with thicknesses comparable to operating wavelengths. The EOT effect is perspective for plasmonic applications in structure-induced colors, optical filtering, lasing, optical biosensors due to the improved signal-to-noise ratio and a simplified device design. Aimed at practically available materials and industrially-compatible surface nanotexturing methods, a systematic study of EOT through continuous aluminum films was performed. A modification of laser interference lithography allowing rapid fabrication of variable depth gratings was proposed, theoretically established and experimentally validated. The variable depth defines the efficiency of plasmonic coupling at a fixed wavelength, offering additional possibilities for light manipulations. Using this approach the existence of optimal grating depth for EOT was demonstrated experimentally and depth-resolved structure-induced colors were observed in transmission. For the first time the effect of EOT was experimentally measured in polycrystalline samples, fabricated via nanosphere photolithography. A phenomenological model of EOT in polycrystaline structures and a dimensionless coefficient of disorder are proposed to explain measured transmission curves. The grating depth and disorder concurrence was studied numerically. The systematic study of EOT in various diffraction systems presented in this thesis might pave the way towards more effective plasmonic devices and industrial applications

The interest for plasmonic nanolasers has been growing in the last ten years, since they are one of the most promising ways to reach the miniaturization of lasers. In fact, these devices could break the limit of physical confinement of light thanks to the virtual cavity given by plasmonic nanostructures which substitutes the current macroscopic optical cavities. These plasmonic devices can also support high speed operation mode, low lasing threshold and a narrow directional emission. For this reason, during this project, we focused on the design, the synthesis and the characterization of plasmonic nanolasers based on Au nanodome arrays and Ag nanodisk arrays. In order to synthesize highly ordered nanostructure arrays, we used Nanosphere Lithography (NSL), which is a cost effective and high throughput technique based on the self-assembling of polystyrene nanospheres. Thanks to the versatility of NSL, we have developed different nanofabrication protocols, combining NSL with Reactive Ion Etching (RIE) and Physical Vapor Deposition (PVD). Therefore, we investigated the optical properties of our synthesized arrays, recreating the optical band structure along the high symmetry directions of the reciprocal space. Suitable dye emitters (Pyridine 2 and Styryl 9M) were selected in order to couple their emission with the optical modes of the nanoarrays, on the basis of optical band structure information. In addition, in order to optimize the plasmonic properties and the local field enhancement of the metallic nanostructures, numerical simulations by COMSOL Multiphysics were performed. The interaction between dye and plasmonic structure generated an amplified emission. In particular, for Au nanodome arrays coupled with Pyridine 2 dissolved in ethanol, an amplification on the emission arises at 720 nm with a threshold behavior at 0.9 mJ/cm^2 and the FWHM of 14 nm. Furthermore, a highly directional emission was obtained at 17° with an angular divergence of 3° which takes place along the Rayleigh anomaly mode. By comparing the results of Au nanodome arrays and silica nanodome arrays, we concluded that lattice modes give a contribution to the emission directionality, while plasmonic modes provide a reduced lasing threshold overcoming the energy loss. Ag hexagonal nanodisk array showed a similar behavior to the Au nanodome arrays: we found a lasing threshold at 1.6 mJ/cm^2 , with also a similar FWHM. In this case, the emission is directed at 65° and presents an angular divergence of about 14° . Moreover, we investigated a nanolaser with a solid-state gain medium for the interest in applications and for the device integration on a chip. The Styryl 9M laser dye is embedded in a PMMA film and coupled with an Au nanodome array. This solid-state system presents an amplified emission at 795 nm with a threshold of 1.2 mJ/cm^2 and a FWHM of about 26 nm. The sample shows also a directional emission at 24° and with an angular divergence of 6° . Further investigations have shown the possibility to eliminate the substrate, creating a self-standing device, which exhibits an amplified emission with similar properties of that with the substrate. Finally, in order to discern the spontaneous or stimulated nature of the emission, we performed coherence measurements of the emitted beam. By a modified Michelson interferometer, a coherence length of about 29 um was determined for Au nanodome arrays above threshold. This result demonstrated that a coherent, low-threshold and highly directional emission can be obtained by coupling a suitable fluorescent dye to a properly designed virtual cavity realized by an ordered array of plasmonic nanostructures.
Nell'ultima decina di anni, l'interesse per i nanolaser plasmonici è cresciuto siccome sono uno tra i modi più promettenti per la miniaturizzazione dei laser. Infatti, questi dispositivi possono superare il limite di confinamento fisico della luce, grazie alla cavità virtuale data dalle nanostrutture plasmoniche che sostituiscono la convenzionale cavità ottica macroscopica. Inoltre, questi dispositivi plasmonici possono supportare modalità di funzionamento ad alta velocità, bassa soglia di emissione laser e una direzionalità ben definita. Per questa ragione, durante questo progetto, ci siamo concentrati sulla progettazione, la sintesi e la caratterizzazione di nanolasers plasmonici basati su array di nanocupole di oro e array di nanodischi di argento. Al fine di sintetizzare reticoli di nanoparticelle con un ordine elevato, abbiamo utilizzato la Nanosphere Lithography (NSL), una tecnica economica e ad alta produttività basata sull'autoassemblaggio di nanosfere di polistirene. Grazie alla versatilità della NSL, abbiamo sviluppato diversi protocolli di nanofabbricazione, combinando la NSL con i processi di Reactive Ion Etching (RIE) e deposizione fisica da vapore (PVD). Successivamente, abbiamo studiato le proprietà ottiche dei campioni sintetizzati, ricostruendo la struttura a bande ottica lungo le direzioni di alta simmetria dello spazio reciproco. Abbiamo selezionato due adeguati emettitori coloranti, la Pyridine 2 e lo Styryl 9M, al fine di accoppiare la loro emissione con le modalità ottiche dei reticoli nanostrutturati, sulla base delle informazioni della struttura a bande ottica. Inoltre, per ottimizzare le proprietà plasmoniche e l'amplificazione del campo locale delle nanostrutture metalliche, delle simulazioni numeriche sono state effettuate tramite il software COMSOL Multiphysics. L'interazione tra il colorante e la struttura plasmonica ha generato un'emissione amplificata. In particolare, nel reticolo di nanocupole di oro accoppiato alla piridina 2 disciolta in etanolo, un'amplificazione dell'emissione si presenta a720nm con un comportamento a soglia a 0.9 mJ/cm^2 . Inoltre, è stata ottenuta un'emissione direzionale a 17° con una divergenza angolare di 3° che avviene lungo l'anomalia di Rayleigh. Confrontando i risultati dei reticoli di nanocupole di oro con quelli dei reticoli di nanocupole di silice, abbiamo concluso che i modi di reticolo danno un contributo alla direzionalità dell'emissione, mentre i modi plasmonici forniscono una riduzione della soglia laser superando così la perdita di energia. Il reticolo esagonale di nanodischi di argento mostra un comportamento simile a quello con le nanocupole di oro: abbiamo trovato una soglia laser a 1.6 mJ/cm^2 , con anche una simile FWHM. In questo caso, questo fascio è diretto a 65° e presenta una divergenza angolare di circa 14° . Inoltre, abbiamo studiato anche un nanolaser con un mezzo di guadagno a stato solido per l'interesse nelle applicazioni e nell'integrazione di dispositivi su chip. Il colorante laser Styryl 9M è incorporato in un film di PMMA e accoppiato con un reticolo di nanocupole di oro. Questo sistema a stato solido presenta un'emissione amplificata a 795 nm con una soglia di 1.2 mJ/cm^2 e una FWHM di circa 26 nm. Questo campione manifesta anche un'emissione direzionale a 24° con una divergenza angolare di 6° . Ulteriori ricerche hanno dimostrato la possibilità di eliminare il substrato, creando un dispositivo autoportante, che presenta un'emissione amplificata con proprietà simili a quella con il substrato. Infine, per discernere la natura spontanea o stimolata dell'emissione, abbiamo misurato la coerenza del raggio emesso. Tramite un interferometro di Michelson dedicato, la lunghezza di coerenza è stimata a circa 29 um per i reticoli di nanocupole d'oro sopra la soglia. Questo risultato ha dimostrato che è possibile ottenere un'emissione coerente, a bassa soglia e altamente direzionale, accoppiando un colorante fluorescente adeguato con una cavità virtuale opportunamente progettata e realizzata da una reticolo ordinato di nanostrutture plasmoniche.

Im ersten Teil der Arbeit werden Signalverstärkungsmechanismen für Raman-Spektroskopie erschlossen und evaluiert. Die als geeignet bewerteten Methoden finden im zweiten Teil ihre Anwendung zur Untersuchung der vibronischen Eigenschaften von dünnen Manganphthalocyaninschichten, die anschließend mit Kalium interkaliert werden. Hierbei sind verschiedene Phasen identifizierbar, die ein ganzzahliges Verhältnis von Kaliumatomen zu Manganphthalocyaninmolekülen besitzen. Im dritten Teil werden die elektrischen Eigenschaften durch die Verwendung dieses Materialsystems als aktives Medium eines Feldeffekttransistors untersucht.

碩士
國立成功大學
光電科學與工程研究所
94
Recently, Nanosphere lithography (NSL) has attracted a lot of interests because it is potentially a low-cost nanofabrication technique Nanostructure fabrications using NSL have been realized by various researchers. In this dissertation, nanofabrication using NSL has been studied and successfully demonstrated. The content of this dissertation is divided into two parts. First, two experimental methods (Drop Method and Capping Method) that lead to the formation of the NSL shadow mask are studied. This shadow mask is composed of a single layer of closed-packed two-dimensional array of nanometer-scaled silica spheres. The experimental conditions for both methods are optimized in order to fabricate a NSL shadow mask that covers a large area. It is observed that the Drop Method usually results in smaller mask area and is not suitable for further nanofabrication. In the other hands, the Capping Method can produce mask with large area and is further studied. The effects of the particle density and the type of solution using the Capping method are investigated. Both are important factors for NSL mask fabrication. Furthermore, a template-assisted NSL mask is also successfully demonstrated. 　　In the second part of this dissertation, the NSL shadow mask is used as the shadow mask for metal depositions. Three types of metals (gold, silver, and aluminum) are selected for due to their visible-near IR localized surface plasmon resonance (LSPR) wavelength. Arrays of metal nano-clusters on top of the substrates are successfully fabricated and can be observed by optical microscope. Absorptions peaks from localized surface plasmon resonance from the metal clusters can be observed in the absorption measurements. The resonance wavelength is found to red-shift when the size of the metal clusters increases. In addition, it is also found that the resonance wavelength is very sensitive to the surrounding of the metal clusters. The resonance wavelength red-shifts when the metal clusters are covered by a thin-film of Silicon oxide. 　　In conclusion, nanofabrication using Nanosphere lithography is successfully demonstrated. It provides a simple and low-cost way to fabricate nanostructures on a flat surface and has huge potential for industrial and research applications.

碩士
國立成功大學
光電科學與工程研究所
95
Fabrications of metallic nanostructures are becoming increasingly important in a variety of scientific applications. In this dissertation, metallic nanoparticle arrays are fabricated using nanosphere lithography. A single layer of nanosphere arrays consisted of nanospheres with diameters of 0.5µm, 0.7µm, 1.0µm, 1.6µm, 2.0µm is utilized as the shadow mask for the metallic nanoparticles arrays. The optimized experimental conditions for the formation of nanosphere arrays are systematically studied. The maximum area of this single layer nsnosphere array can be obtained is approximately 30mm x15 mm limited by the current experimental instruments. It is also able to form a single layer of nanosphere arrays within a pre-patterned 60 �慆-wide trench. O2 plasma etching is also able to reduce the size of polystyrene nanospheres. The absorption spectra from Ag nanostructures fabricated with nanopshere lithography exhibit responses from localized surface plasmon resonant scattering (SPRS) from the Ag nanostructures. The observed localized surface plasmon resonance blue-shifted as the size of metallic nanoparticle decreased. The resonance also blue shifted as the shape of metallic nanoparticle changed from a triangular form to a circular form. The application of Ag nanostructures in organic solar cell is also investigated. The power conversion efficiencies of the solar cell with Ag nanoparticles (2.42%) are higher than the device with Ti nanoparticles (1.68%). Effect from the surface plasmon resonance scattering is a possible cause for this enhanced power conversion efficiency.

碩士
國立交通大學
電子物理系所
106
The benefits for nanowire device applications are based on quantum confinement effect and larger surface. The important requirement of that is the precise control of GaN nanowires with well uniformity. In addition, investigating the key factor to determine the growth orientations of nanowires is important for nanowire devices To reduce substrate cost and integrate with silicon, the bottom-up method via HVPE is used to grow GaN nanowires with Au/Ni catalysts on the low-cost Si(111). However, the average diameter and growth locations of nanowires are nonuniform due to the Au/Ni droplets with random sizes and locations before nanowires growing. The Au/Ni catalysts-assisted method is based on the VLS or VSS growth mechanism. According to both growth mechanisms, the average diameter of the nanowires are almost the same size as the tip of the catalyst, so nanosphere lithography (NSL), an effective method, is introduced to improve the uniformity. The NSL improvement is achieved by controlling the large-area catalyst positions and sizes to define where the nanowires grow and make the diameters of nanowires more consistent. The main growth orientation of the GaN nanowires grown via Au/Ni catalysts on four different substrates or grown via different catalysts on Si (111) is m-plane, so there is no direct relation between the growth orientation and the lattice structure of substrate or different catalysts under our growth conditions. In summary, the growth orientation is almost consistent, so the VLS growth mechanism is dominant. The key factor to determine the growth orientation of GaN nanowires is that at the initial nucleation phase, the composition of Ga-part in the liquid droplet is low, which leads to the non-polar m-axis GaN nanowire growth.

碩士
國立成功大學
光電科學與工程研究所
96
In this thesis, the improvement of nanosphere lithography (NSL) and the template-assisted nanosphere lithography were both reported. Nanosphere lithography utilizes one single layer of close-packed nanosphere arrays as a shadow mask to fabricate periodic nanostructure on top of different substrates and has been developed in our group for several years. Large area (30 mm × 15 mm) consists of one single layer of nanosphere arrays can be fabricated. However, we have difficulties to deposit metal through this single layer of nanosphere arrays. In this research, the residue of surfactant located between spheres was identified to be the origin of this problem with the help from scanning electron microscopy. By annealing in high temperature or treating with oxygen plasma, the residue can be effectively removed and large area (20μm × 20μm ) of metallic nanoparticles arrays can be fabricated. Template-assisted nanosphere lithography was also developed in this research. Nanosphere arrays were fabricated inside the photolithography-fabricated patterns. The effects of various parameters were studied and optimized to fabricate a single layer of nanosphere arrays. The arrays were subsequently treated with reactive ion etching (RIE) to slightly reduced the size of the sphere. After depositing metal through the remaining nanosphere arrays, large area of periodic nano-hole arrays can be fabricated. However, the limitation of the RIE using a metallic hard mask has delayed further developments of the template-assisted nanosphere lithography. Therefore, modification of the process is required to avoid the metallic hard mask. We believe that template-assisted nanosphere lithography can be applied in several important optoelectronic devices and advanced their device performance.

碩士
國立交通大學
材料科學與工程學系
100
When the light impinges the interface between two different media, some of light is reflected at interface. The reflection creates many problems, such as flare and glare, and may reduce the performance of electro-optical devices. Traditionally, a coating of dielectric thin film with low refractive index was used to reduce the reflection. But the coating can only suppress the reflection in a single or narrow-band wavelength. However, the reflection can be reduced in broadband, if the surface has nanoscale protuberance arrays. In this study, we developed a process to fabricate the protuberance arrays on quartz surface using nanosphere lithography and two different polystyrene (PS) sphere sizes, 600 nm and 200 nm. First, the polystyrene sphere arrays can be prepared on the quartz surface by a self-assembly technique. The protuberance arrays on quartz surface were then fabricated by CF4 reactive ion plasma etching under the masking of polystyrene sphere. Different profiles of protuberances such as spot-like, truncated-cone, and paraboloid-like shapes can be made and controlled by etching time. At fixed CF4 flow rate and pressure, the aspect ratio of paraboloid-like protuberance arrays of 200 nm in period is about 1.35 and 1.15 for 600 nm PS sphere arrays as a mask. In addition, the quartz surface with paraboloid-like profile arrays is found to show better transmittance than other structures. Simulations were also carried out to assess if the paraboloid-like profile arrays on the quartz surface have the potential to enhance the light power in OLED. The light power of OLED as a function of different period and height in the paraboloid nanostructure was calculated using FullWAVETM, a finite-difference time-domain (FDTD) simulator. When the period of protuberance is 200 nm and the aspect ratio of protuberance is 3, the light power of OLED substrate with paraboloid-like protuberance arrays shows 14% increase.

碩士
國立成功大學
光電科學與工程研究所
98
In this dissertation, various nanofabrication techniques using nanometer-sized colloids are developed and different types of nanoparticle arrays are successfully fabricated. Large areas (~ 3 mm x 3 mm) of ordered periodic arrays are obtained by all methods investigated. First, metal nanoparticles arrays were fabricated using conventional Nanosphere Lithography (NSL). Localized surface plasmon resonances (LSPR) of these nanoparticles made from different metal were investigated. LSPR experiences red-shift as the physical sizes increase or higher-refractive-index substrate was used. Second, NSL combining with oxygen plasma treatments was demonstrated to be able to fabricate metallic nanotriangles with different side length. LSPR also red shifts as the size of the nanotriangles increases due to oxygen plasma etching. Oxygen plasma etching also reduced the gap distance between nanotriangles. The smallest gap distance fabricated was estimated to be 40 nm. Nanotriangles pairs with sub-100nm gap are referred as bowtie nanoantennas that are of great importance in Nanophotonics. LSPR of the nanoantenna was observed to red-shifted as the gap distance decreased. In addition, preheated nanosphere solution was used along with the plasma-treated NSL. This method can fabricate bowtie nanoantenna with very narrow and uniform gap separation that regular plasma-treated NSL can not obtain. Third, two-dimensional circular nanodisk arrays were also fabricated by using Nanospherical Lens Lithography (NLL). Nanodisks with diameters between 800 to 960 nm were fabricated using 1 μm polystyrene nanospheres as the lithographic mask. 500 nm polystyrene nanospheres were also demonstrated to obtain similar results. Plasmonic properties of Metal-Insulator-Metal nanodisks using NLL were investigated. LSPR mode splitting was observed in the transmission spectra for nanodisk arrays with different disk diameters. In conclusion, nanofabrication techniques using Nanosphere Lithography, Plasma-treated NSL, Plasma-treated NSL using pre-heated nanospheres, and Nanospherical Lens Lithography were developed in this research. Each of the techniques can fabricated large-area ordered nanoparticles arrays with low fabrication cost. The future applications for these fabricated arrays can contribute greatly in Nanophotonics and offer exciting experimental results.

碩士
國立中興大學
材料科學與工程學系所
99
With the shrinking of the dimensions of electronic devices, the-low resistivity and high-stability metal silicides have been widely used as the contacts on source, drain, gate in transistors to reduce contact resistance. Preferred silicides for the applications are titanium silicide (TiSi2), cobalt silicide (CoSi2) and nickel silicide (NiSi). Because NiSi has a wide process window, less silicon consumption, low film stress, nickel silicide is consider to be the most promising candidate for scaled devices below one hundred nanometers. In the study of nanoelectronic devices, carbon nanotubes (CNT) and silicon nanowires (SiNW) have been used as building blocks. However, the structure and size of CNTs is difficult to control process. The size of SiNWs can be controlled by a lithography technology, and can be integrated with semiconductor process. Therefore, SiNW has advantage over CNT. As the semiconductor industry continues to shrink the dimensions of electronic devices, the study of properties of metal silicide nanowires becoming more and more importance. In this study, a large number of nanowires with a controlled diameter, growth orientation were fabricated by combining polystyrene nanosphere lithography with metal-induced catalyst etching. Then, nickel silicide/ silicon heterostructure nanowires were formed by glancing angle deposition technique and solid-phase reaction. The effects of the size of Si nanowires on the formation of nickel silicide and the electrical property of nickel silicide/silicon interfaces in heterostructure nanowires were investigated. The results show that nickel silicide/silicon heterostructure nanowires were fabricated successfully. The front-end of nickel silicide part is Ni3Si2, The silicides formed at the silicide/silicon interface were NiSi and NiSi2 in the thinner nanowires (diameter≦105nm) and the thicker nanowires (diameter≧110nm), respectively, which is because that the formation of nickel silicide was a surface diffusion controlled process. The interfacial electrical properties of NiSi/silicon hetrojunction (in the thinner nanowires) and NiSi2/silicon hetrojunction (in the thicker nanowires) were Schottky contact and Ohmic contact, respectively.

碩士
國立中央大學
化學工程與材料工程研究所
96
In the present study, we have demonstrated that 2D periodic arrays of nickel metal and silicide nanodots can be successfully fabricated on (111)Si substrates by using the polystyrene (PS) nanosphere lithography (NSL) technique and thermal annealing. The results of an investigation on the interfacial reactions between the Ni nanodots and (111)Si substrates after different heat treatments are reported. From the TEM and SAED analysis, only epitaxial NiSi2 nanodots were found to form on (111)Si at a temperature as low as 300 °C. The results indicated that the growth of epitaxial NiSi2 is more favorable for the samples with smaller Ni nanodot sizes. The epitaxial NiSi2 nanodots were found to grow with an epitaxial orientation with respect to the (111)Si substrates: [111]NiSi2//[111]Si and {220}NiSi2//{220}Si. In addition, these epitaxial NiSi2 nanodots formed on (111)Si were observed to be heavily faceted and the faceted edges of the NiSi2 nanodot were identified to be parallel to <1 0>Si directions. On the other hand, during the experiments, the double-layered arrays of PS spheres were occasionally found to form on silicon substrates. The epitaxial NiSi2 nanodot arrays formed from the bilayer masks exhibit larger interparticle spacings and smaller particle sizes. By combining the nanosphere lithography, heat treatments, wet chemical etching and electrodeposition techniques, we also successfully fabricate large-area shape- and size-tunable metal nanostructures (nanobowls and nanopillars) and nanohole arrays on Si and SiGe substrates. The morphology evolution, size uniformity and crystal structure of the produced nanostructures have been systematically investigated by SEM, AFM, TEM, and SAED analyses. The observed results present the exciting prospect that with appropriate controls, the colloidal NSL technique promises to offer an effective and economical patterning method for fabrication of a variety of well-ordered nanostructures with selected shape, size, and periodicity on different substrates without complex lithography.

博士
中華大學
工程科學博士學位學程
101
Periodic nanostructures have recently gained widespread attention because of their unique properties and promising applications in numerous fields, such as sensors, photonic crystals, and optoelectronic devices. Various techniques can be used to fabricate periodic arrays of nanostructures, including X-ray lithography method, electron-beam lithography (EBL), and interference lithography (IL). Although these lithographic techniques have been used to control the morphology of the periodic structure arrays, they are time consuming and costly. Hence, researchers have focused on the study of simple, high-resolution and low-cost nanosphere lithography (NSL) technique to fabricate periodic nanostructure arrays. This dissertation investigates the structure, morphology, wettability, and optical properties of Cr, CrN, and polycarbonate (PC) nanostructure patterns using technology based on NSL. The content of this dissertation is divided into three sections. Firstly, this study shows the effect on their capillary force and convective flux properties associated with controlling the spin speed of the spin coater and concentration of the polystyrene (PS) nanosphere solution. A monolayer of nanospheres with a hexagonal close-packed array structure was formed on glass substrates using the spin-coating method. The size and shape of the size-tunable ordered PS nanosphere arrays structure can be manipulated using the reactive ion etching (RIE) process. The second section of this dissertation investigates the fabrication of hierarchical porous Cr nanoring array patterns using a magnetron sputtering process and NSL-based technique. To study the optical effects of the substrate and the Cr ring-shaped nanostructure film, different nanosphere sizes and deposition thicknesses are introduced to adjust the size and shape of the ring-shaped nanostructures. The optical transmittance of porous Cr nanoring arrays can be enhanced using surface plasmon resonance. The luminous enhancement at a special wavelength of 525 nm and better color purity were observed in this Cr nanoring structure. This new approach has various potential applications in optoelectronic devices and optical sensors. The third section of this dissertation shows that the surface of the nanomold of CrN nanohole arrays has a low surface energy. The optical properties of the antireflective PC-tapered nanopillar layer were successfully replicated from the CrN nanomold. These antireflective surfaces are promising for the fabrication of antireflective surface structures with various bands, and these antireflective optical materials have wide applications in various optoelectronic products.

碩士
國立臺灣大學
光電工程學研究所
104
In this dissertation, we will demonstrate the fabrication of various nanoscale optoelectronic devices using a low-cost nanofabrication method developed from Nanosphere Lithography (NSL). First, we will discuss how to use a top-down nanofabrication approach to fabricate silicon nanonet field-effect transistors (FETs). We will also discuss the electric properties of these FETs and apply them for biosensing application. In the final part of this these, I will discuss how to use the two-step etch technique and regular photolithography to fabrication InGaN/GaN cavity LED. The basic electric and optical properties will also be discussed.

碩士
中興大學
材料工程學系所
95
Patterned media can reduce the intergranular interaction between the magnetic grain particles. This feature can reduce the noise signal generation in hard disk and if incorporate with high Ku value material can also slacken the superparamagnetism effect to occur and hence obtain a higher recording density. Nanosphere lithography has advantages such as low-cost, high-throughput and can efficiently producing large scale well-ordered 2D periodical arrays in nano-structures. This study using the self- assembly capability of nanosphere to producing high Hc alloy type Sm-Co, Fe-Pt nano dots array and soft magnetic material Co dots. The outcome was then used to analysis the relationship between magnetic nano-particle domain wall structure transformation and intergranular interaction. From the experiment result, it shows that using 508nm nanosphere mask can obtain 178nm Fe-Pt nano dots array. Without external field exertion, the dots array is usually multi-domain structure and with annealing treatment at temperature 600℃, the Hc value can rise to 4.42kOe. The experiment results showed that covering the Fe-Pt dots array with 10nm cobalt thin film can significant increasing the Hc value of the cobalt film which is single domain structure with the same dipole rotation direction.

碩士
國立中興大學
材料科學與工程學系所
106
Metal mesh has high light transmission, high conductivity and high flexibility, so it is considered to be used to replace the indium tin oxide(ITO)which is commonly used for transparent conductive electrode. We use nanosphere lithography to prepare silver metal mesh.the advantages of nanosphere lithography are low cost and convenient. Since silver is easily oxidized to silver oxide, indium-zinc-oxide (ITZO) is deposited to protect silver. ITZO has good photoelectric properties in the normal temperature process, and it can also improve the overall light transmission. We have successfully prepared single layer closed-packed structure of 800nm and 2000nm polystyrene spheres.Metal mesh was obtained by oxygen plasma etching the nanosphere template、sputtering and nanosphere lift-off. It can be known from the experiment that as the thickness of silver increases, the light transmission decreases, and the light reflection increases.In the infrared light region,we also observe the extraordinary optical transmission.This phenomenon is related to the resonance coupling of the surface plasma and the electromagnetic wave. The meshes prepared by using 800nm and 2000nm polystyrene as templates have the highest figure of merit in Ag 20nm/ITZO 40nm and Ag 30nm/ITZO 40nm respectively, and their values are 3.1mΩ-1 and 1.1mΩ-1. It can be known from the experiment that during the sputtering process, the atoms will scatter into the bottom of the nanosphere.It causes the line width of mesh to increase and the light transmission to decrease, thereby degrading the figure of merit. The mesh prepared by using 2000 nm polystyrene as a template has high light transmission,but since the line width of mesh is partially discontinuous,the resistance value is increased, and the figure of merit is decreased.

碩士
國立臺灣大學
應用物理研究所
105
In this study, we will demonstrate several nanoscale optoelectronic devices fabricated using Nanosphere Lithography (NSL). First, periodic nanoparticles and inverted pyramid nanostructures are fabricated on top of flexible substrates using template-stripping method. Optical properties of these nanostructures are investigated experimentally and verified theoretically by using finite-difference time domain (FDTD) methods. Second, optical properties of periodic aluminum nanodisks are also investigated and the simulated extinction spectra reveal a tunable lattice plasmon mode peak within the visible spectra range. We will cover the fabricated nanodisks arrays with gain materials to study the lattice plasmon assisted lasing. In the last part of this dissertation, we will demonstrate the fabrication of silicon nanonet field-effect transistors (FETs). The electric properties of these nanonet FETs are investigated. We will also discuss the results measured by these Si nanonet FETs for chemical and biosensing applications.

碩士
國立清華大學
光電工程研究所
101
GaN material has a great development space for blue LED. However, lattice mismatch exists between GaN and substrate material, so it is restricted to be used. Recently, GaN-based LED grown on a patterned sapphire substrate (PSS) is widely studied. It can not only efficiently reduce threading dislocation (TD) density of GaN grown on, but also enhance light extraction efficiency as well. We successfully fabricate PSS of different scales by nanosphere lithography and compare the characteristics of GaN on each substrate. We compared the quality of GaN films grown on them by PL and XRD. The results indicate that the quality is the best when grown on pattered sapphire substrates with period 100 nm and duty ratio 100%. The results match. We can conclude that the quality of GaN films is better when grown on PSS with smaller period and larger duty ratio.

碩士
中原大學
化學工程研究所
101
In this study, polystyrene and PET polymers covered with silica nanospheres in the form of monolayer were modified by CF4 plasma to form nanostructured surface. The plasma diagnostics (OES) and surface analysis (CA, FE-SEM, XPS, UV-vis) were used to elucidate the process-structure-property relationship. The results revealed that super-hydrophobic surface with water contact angle of 155° were achieved on polystyrene polymers. The surface consisted of nano-pillars of about 300 nm in height and 100 nm in diameter, and the fluorine-to-carbon atomic ratio was about 0.8. The surface was also oleophobic as the CH2I2 contact angle reached 110°. Moreover, the surface exhibited good self-cleaning effect and visible light transmittance. Due to its high oxygen content in the pristine PET polymer, the CF4 plasma modified PET surface was not super-hydrophobic. Although nano-pillars were formed on PET surface, but its fluorine-to-carbon ratio was lower and oxygen-to-carbon ratio was higher than the plasma modified polystyrene. Therefore, a thin layer of fluorocarbon film of about 30 nm was deposited on CF4 plasma modified PET surface. Consequently, the surface hydrophobicity (~169°) and fluorine-to-carbon ratio (1) was increased dramatically and oxygen-to-carbon ratio was significantly decreased. The modified PET surface exhibited excellent self-cleaning effect since the WCA hysteresis was about 5° and the sliding angle was less than 8° in dynamic contact angle analysis.

碩士
國立中央大學
光電科學與工程學系
102
Surface enhanced Raman scattering (SERS) active silver periodic particle array (PPA) substrates are fabricated by nanosphere lithographic technique. Base on the reported results in literatures, the shift of plasmon resonance wavelength can be manipulated via varying the fabrication parameters such as particle size, thickness and shape. Experimentally, thermally induced shape change was observed which results in the red shift of the resonant wavelength. The result is in close agreement with that obtained by Van Duyne. In addition, a local site on the PPA with resonance wavelength close to =532 nm was chosen to examine the resonant Raman response from model molecule Rhodamine 6G (R6G). The measured Raman spectrum, clearly reveals the vibrational fingerprint of the R6G molecule, demonstrating the enhancement capability of the fabricated substrate for molecular analysis substrate. Finally, fluorescence life time measurement of R6G on various substrates was conducted by TCSPC system, with the aim to justify the interplay between substrate quenching effect and the enhancement factor of R6G.

abstract: In this thesis, a novel silica nanosphere (SNS) lithography technique has been developed to offer a fast, cost-effective, and large area applicable nano-lithography approach. The SNS can be easily deposited with a simple spin-coating process after introducing a N,N-dimethyl-formamide (DMF) solvent which can produce a highly close packed SNS monolayer over large silicon (Si) surface area, since DMF offers greatly improved wetting, capillary and convective forces in addition to slow solvent evaporation rate. Since the period and dimension of the surface pattern can be conveniently changed and controlled by introducing a desired size of SNS, and additional SNS size reduction with dry etching process, using SNS for lithography provides a highly effective nano-lithography approach for periodically arrayed nano-/micro-scale surface patterns with a desired dimension and period. Various Si nanostructures (i.e., nanopillar, nanotip, inverted pyramid, nanohole) are successfully fabricated with the SNS nano-lithography technique by using different etching technique like anisotropic alkaline solution (i.e., KOH) etching, reactive-ion etching (RIE), and metal-assisted chemical etching (MaCE). In this research, computational optical modeling is also introduced to design the Si nanostructure, specifically nanopillars (NPs) with a desired period and dimension. The optical properties of Si NP are calculated with two different optical modeling techniques, which are the rigorous coupled wave analysis (RCWA) and finite-difference time-domain (FDTD) methods. By using these two different optical modeling techniques, the optical properties of Si NPs with different periods and dimensions have been investigated to design ideal Si NP which can be potentially used for thin c-Si solar cell applications. From the results of the computational and experimental work, it was observed that low aspect ratio Si NPs fabricated in a periodic hexagonal array can provide highly enhanced light absorption for the target spectral range (600 ~ 1100nm), which is attributed to (1) the effective confinement of resonant scattering within the Si NP and (2) increased high order diffraction of transmitted light providing an extended absorption length. From the research, therefore, it is successfully demonstrated that the nano-fabrication process with SNS lithography can offer enhanced lithographical accuracy to fabricate desired Si nanostructures which can realize enhanced light absorption for thin Si solar cell.
Dissertation/Thesis
Doctoral Dissertation Materials Science and Engineering 2015

A highly compact, one diode-one resistor (1D-1R) SiOx-based resistive switching memory device with nano-pillar architecture has been achieved for the first time using nano-sphere lithography. The average nano-pillar height and diameter are 1.3 μm and 130 nm, respectively. Low-voltage electroforming using DC bias and AC pulse response in the 50ns regime demonstrate good potential for high-speed, low-energy nonvolatile memory. Nano-sphere deposition, oxygen-plasma isolation, and nano-pillar formation by deep-Si-etching are studied and optimized for the 1D-1R configurations. Excellent electrical performance, data retention and the potential for wafer-scale integration are promising for future non-volatile memory applications.
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博士
國立清華大學
材料科學工程學系
100
The energy level alignment between a metal and an organic semiconductor (M/O) is regarded as the dominant factor affecting carrier injection efficiency. In particular, it plays a crucial role in the performances of organic light emitting diodes (OLEDs) including electroluminance efficiency and life-time. Through electrode surface modification, the size and direction of the interface dipole can be introduced to modulate the energy alignment at the interface. In this study, a series of thiol compounds, including fluorine-substituted benzyl mercaptans, n-alkanethiol, cyano-terminated (CN-), trifluoro-terminated (CF3-), perfluroinated substituents and binary mixtures with opposite dipoles, were used to modify the silver anode through the formation of well-ordered self-assembled monolayers (SAMs) and applied in the fabrication of top-emitting electroluminescent devices. The device performances were measured and analyzed to understand the effect of modification on the charge injection. It is demonstrated that the same substituent placed at different positions on a phenyl ring results in different dipole moment and modulate the work function/charge injection differently. Furthermore we demonstrated that besides the dipolar functional group, the chain length of alkanethiol can be used to tune the tunneling distance for charge injection. Through selection of the two parameters (dipolar functional group and tunneling distance), the energy alignment can be fine-tuned and influence the charge balance and luminescence efficiency. VII Furthermore, SAMs of binary mixtures of n-decanethiol and the perfluorinated analogue were formed on silver surface. Through change of mixing ratio, the work function of silver can be tuned continuously over a wide range: from 4.1 eV to 5.8 eV. The mixed SAM-modified Ag surfaces were used as the anode in the fabrication of hole-only devices and electroluminescent devices using different hole-transporting materials (HTL). Through the analysis of charge injection efficiency/luminescence efficiency, strategy of improving hole/electron carrier balance is proposed. With generally low mobility associated with organic semiconductors and limitations on the fabrication involving lateral transistors as driving component, we also extended our work on vertical type transistors, which uses greatly reduced channel length to lower driving voltage and increase current output. A large-area and periodically patterned nanoporous Al grids with controlled pore size were fabricated by poly(ethylene oxide)-assisted self-assembly of polystyrene nanospheres. This grid layer was used as the base electrode in a space-charge limited transistor (SCLT) with vertical architecture. A high performance device with poly(3-hexylthiophene) (P3HT) as conducting semiconductor was achieved with a high on-current

博士
國立交通大學
應用化學系碩博士班
100
This thesis is focus on the anti-reflection and luminescent down-shifting property of silicon solar cell. The content is divided into three parts：(1) Nanoparticles_Silica (2) Nano-Honeycomb Structure Layer (3) Nano-Phosphors_YVO4：Bi3+：Eu3+. Part one: In this study, silica nanospheres dispersed in a surfactant solution were spin-coated on commercially available silicon solar cells to form colloidal crystals on the surface. This self-assembled nanoparticle layer served as an anti-reflection (AR) layer for solar cell devices. The self-assembled layer exhibits excellent anti-reflection properties in the UV and NIR wavelength regions. We also showed that the overall conversion efficiency of polycrystalline Si solar cells coated with the silica nanospheres was increased from 11% to 12.3% when using optimized spin-coating parameters and nanoparticle concentrations. Part two: This experiment demonstrates the process for manufacturing a ZnO honeycomb sub-wavelength structure using nanosphere lithography technology exhibiting excellent anti-reflection properties from the UV to NIR wavelength regions. This honeycomb nanostructure, combined with commercially available crystalline Si solar cells, show substantially improved conversion efficiency from 15.6% to 16.6% using optimized honeycomb sizes and precursor concentrations of ZnO. The present work develops an unsophisticated and economical technique suitable for industrial applications in producing a uniform and low-reflective texture. Part three: The colloids of YVO4 nanoparticles on micro-textured Si surface are demonstrated to have promising potential for efficient solar spectrum utilization in crystalline Si solar cells. The solar cells showed an enhancement of 4% in short-circuit current density and approximately 0.7% in power conversion efficiency when coated with YVO4 nanoparticles. The properties of cells integrated with YVO4 nanoparticles were characterized to identify the role of YVO4 in improved light harvesting. The current experiments conclude that the colloids of YVO4 nanoparticles not only act as luminescent down-shifting centers in the ultraviolet region but also serve as an anti-reflection coating for enhancing the light absorption in the measured spectral regime.