Nanofabrication has received substantial interest from scientists and engineers because of its potential applications in many fields. This was because nanoscale structures have unique properties that cannot be observed or utilized at other size scales. Our living environment and many of our daily necessities had been strongly influenced by these techniques. Computers, electronics, housewares, vehicles, and medical care are now all affected by this explosive nanotechnology. However, traditional methods in controlling nanoscale features and their properties were often time-consuming and expensive. The objective of my research was to design, fabricate, and test nanostructure platforms using a unique toolbox of bottom-up lithographic techniques recently developed in our laboratory. These novel methods can be utilized for the rapid prototyping of nanoscale patterns in a much easier and more economical way. Specifically, we also focused on applying these nanoscale patterns as sensor platforms. These platforms were easily produced with our unique methods, and provide ultra sensitive capability to detect diverse chemical or biological species. The demonstration of capabilities and applications of our unique technologies includes the following projects. Chapters II and III describe a simple, inexpensive, and rapid method for making metal nanoparticles ranging between 10 nm and 100 nm in size through metal photoreduction with templates. The process can be completed in approximately 11 minutes without the use of a clean room environment or vacuum techniques. A simple label-free biosensor fabrication method based on transmission localized surface plasmon resonance (T-LSPR) of this platform is also demonstrated. Chapters IV and V present a nanoscale patterning technique for creating diverse features in polymers and metals. The process works by combining evaporative ring staining with a colloidal templating process. Well-ordered hexagonally arrayed nanorings, double rings, triple rings, targets, and holes were all easily prepared. A line width as thin as ~15 nm can repeatably be performed with this technology. Finally, Chapter VI demonstrates an ultra-sensitive plasmonic optical device based on hexagonal periodic nanohole metal films produced through our evaporative templating technique. The optical properties of these sub-wavelength periodic hole array metal films are discussed.

Nanofabrication has received substantial interest from scientists and engineers because of its potential applications in many fields. This was because nanoscale structures have unique properties that cannot be observed or utilized at other size scales. Our living environment and many of our daily necessities had been strongly influenced by these techniques. Computers, electronics, housewares, vehicles, and medical care are now all affected by this explosive nanotechnology. However, traditional methods in controlling nanoscale features and their properties were often time-consuming and expensive. The objective of my research was to design, fabricate, and test nanostructure platforms using a unique toolbox of bottom-up lithographic techniques recently developed in our laboratory. These novel methods can be utilized for the rapid prototyping of nanoscale patterns in a much easier and more economical way. Specifically, we also focused on applying these nanoscale patterns as sensor platforms. These platforms were easily produced with our unique methods, and provide ultra sensitive capability to detect diverse chemical or biological species. The demonstration of capabilities and applications of our unique technologies includes the following projects. Chapters II and III describe a simple, inexpensive, and rapid method for making metal nanoparticles ranging between 10 nm and 100 nm in size through metal photoreduction with templates. The process can be completed in approximately 11 minutes without the use of a clean room environment or vacuum techniques. A simple label-free biosensor fabrication method based on transmission localized surface plasmon resonance (T-LSPR) of this platform is also demonstrated. Chapters IV and V present a nanoscale patterning technique for creating diverse features in polymers and metals. The process works by combining evaporative ring staining with a colloidal templating process. Well-ordered hexagonally arrayed nanorings, double rings, triple rings, targets, and holes were all easily prepared. A line width as thin as ~15 nm can repeatably be performed with this technology. Finally, Chapter VI demonstrates an ultra-sensitive plasmonic optical device based on hexagonal periodic nanohole metal films produced through our evaporative templating technique. The optical properties of these sub-wavelength periodic hole array metal films are discussed.

Superconducting nanowire single photon detectors (SNSPDs) can detect single photons or low levels of infrared light in applications that require high speed and low timing jitter, such as integrated circuit analysis. Most applications also require a high device detection efficiency (DDE), but the DDE of SNSPDs is limited by many factors. A good optical design with an integrated optical cavity and dielectric layers can increase the absorptance of 1550-nm light in the active area to over 90%. Therefore, optical modeling using the transfer matrix method was used to guide the design and fabrication of high-efficiency detectors with a measured DDE of over 70%. In addition, finite element analysis was used to simulate the effect of adding different types of optical antennas to SNSPD designs to increase their active area without compromising their speed, and the fabrication of antennas integrated with nanowires achieved sub-10 nm gaps between features. Thin films of niobium nitride, the starting material of the SNSPDs, were investigated using several techniques for thin film characterization, including x-ray diffraction, Auger electron spectroscopy and x-ray photoelectron spectroscopy. Optical setups based on reflectometry and transmittometry were built to determine the film thickness more accurately than deposition time for optical modeling and to provide feedback on the deposition conditions. The optical setups are able to provide reproducible and precise thickness measurements to within 0.1 nm. / Engineering and Applied Sciences

The discovery of large, room temperature magnetoresistance (MR) in magnetic tunnel junctions in 1995 sparked great interest in these devices. Their potential applications include hard disk read head sensors and magnetic random access memory (MRAM). However, the fabrication of repeatable, high quality magnetic tunnel junctions is still problematic. This thesis investigates methods to improve and quantify the quality of tunnel junction fabrication. Superconductor-insulator-superconductor (SIS) and superconductor-insulator ferromagnet(SIF) tunnel junctions were used to develop the fabrication route, due to the ease of identifying their faults. The effect on SIF device quality of interchanging the top and bottom electrodes was monitored. The relationship between the superconducting and normal state characteristics of SIS junctions was investigated. Criteria were formulated to identify devices in which tunneling is not the principal conduction mechanism innormal metal-insulator-normal metal junctions. Magnetic tunnel junctions (MTJs) were produced on the basis of the fabrication route developed with SIS and SIF devices. MTJs in which tunneling is the principal conduction mechanism do not necessarily demonstrate high MR, due to effects such as magnetic coupling between the electrodes and spin scattering. Transmission electron microscope images were used to study magnetic tunnel junction structure, revealing an amorphous barrier and crystalline electrodes. The decoration of pinholes and weak-links by copper electrodeposition was investigated. A new technique is presented to identify the number of copper deposits present in a thin insulating film. The effect of roughness, aluminium thickness and voltage on the number of pinholes and weak-links per unit area was studied. High frequency testing of read heads at wafer level was performed with a network analyser. Design implications for read head geometry were investigated, independent of magnetic performance. This technique has great potential to aid the rapid development of read and write heads whilst improving understanding of the system.

The aim of the thesis is to fabricate Schottky contact carbon nanotube field effect transistor (CNFET) using the dielectrophoresis (DEP) to resolve the alignment issue and show its transistor behaviour. The work presented is a combination of fabrication and simulation of CNFET. Fabrication of the device electrode had been done using the electron beam lithography to achieve a channel length of 150nm and analysis was done on an optical microscope, SEM, AFM and Raman spectroscopy. Second half of the thesis provides a solution to “bottleneck communication” between microprocessor and memory to increase the computation for applications like AI, IoT etc and 3D monolithic memories. As a solution, we propose a novel CNFET based processing in-memory architecture using a novel CNFET dual port single-ended SRAM bit cell. The combination of the CNFET and processing in-memory can be a new phase for memory and computation.

Thesis advisor: Kenneth S. Burch / In condensed matter physics we study the behavior of crystals at finite density and low temperatures. By tuning and breaking the various materials, symmetries, and the topology of a crystal one can bring about brand new quantum phases of matter. These new phases of matter in turn produce emergent quasiparticles such as the cooper pair in superconductivity, the spinon in magnetic systems, and the Fermi arcs in Weyl semimetals. Of particular interest are systems in which superconductivity interacts with topology. These systems have been theoretically predicted to produce anyonic quasiparticles which may be used as qubits in a future fault-tolerant quantum computer. However, these ideas usually require the use of the superconducting proximity effect to inject cooper pairs into the topological system. This in turn requires interfacing two different materials which not only requires extremely clean interfaces, but also matching Fermi surfaces, comparable Fermi velocities, and more. The ideal candidate for topological superconductivity would therefore be a material that is both superconducting and topologically non-trivial. One promising candidate is the iron-based superconductor FeTe(1−x)Sex, specifically at the FeTe0.55Se0.45 (FTS) doping which also has non-trivial topology. In this dissertation, we address the fabrication of pristine interfaces using a new tool as well as new probes into the topology of FTS. In Chapter II we discuss the motivation, construction, and use of the “cleanroomin-a-glovebox”. This tool places an entire nanofabrication workflow into an inert argon atmosphere which has allowed us access to study a myriad of new materials and systems. A delightful offshoot of this glovebox is that it is a useful tool in training new scientists in fabrication techniques. The photolithography, Physical Vapor Deposition (PVD), and characterization tools in the glovebox are designed to be easy to use and thus afford new users a low-risk method of learning new techniques. In chapter III we discuss a specific example of a new quantum phase of matter e.g. topological superconductivity in FTS. There, I discuss the fabrication requirements to probe this elusive phase as well as the unique measurement technique used to provide evidence that FTS is a higher-order topological superconductor. The characterization of FTS continues in Chapter IV where we reveal some exciting new results in the FTS system. These new results are direct evidence for the topological nature of FTS, a feat which has only been shown in Angle-Resolved Photo Emission Spectroscopy (ARPES) and Scanning Tunneling Microscopy (STM). Chapter V concludes the dissertation with a summary of Chapters II, III, and IV. In addition, we give suggestions for future experiments to investigate the FTS system further as well as suggestions for insightful teaching programs with the cleanroom-in-a-glovebox. / Thesis (PhD) — Boston College, 2021. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Physics.

La synthèse contrôlée de nanoparticules métalliques (NPM) selon des morphologies et dimensions particulières est un domaine de recherche interdisciplinaire en raison des nouvelles propriétés physiques variées, riches et complexes des NPM. Ces propriétés sont principalement régies par les oscillations collectives des électrons de conductions appelées « plasmons ». Ce phénomène se traduit optiquement par une sensibilité des NPM au moindre changement d’indice de réfraction par déplacement de leur bande de résonance plasmon. Ce phénomène en fonction de la morphologie des NPM est mis à profit dans applications assez modernes telles que la photothérapie contre le cancer et l’élaboration de capteurs ultrasensibles basés sur la Résonance Plasmon de Surface (SPR) ou sur la Spectroscopie d’Exaltation Raman de Surface (SERS). La sensibilité des NPM en tant que capteurs est directement liée à la nature chimique et cristalline du métal mais également à leur capacité à adsorber les molécules cibles, à absorber ou/et confiner et exalter la lumière incidente. Cette dernière propriété est généralement d’autant plus remarquable que la distance séparant les NPM est petite. Ainsi, le contrôle de la taille, forme et densité des NPM présente un intérêt majeur et les travaux visant à développer de nouvelles méthodes de fabrication ou de nano-structuration sont toujours d’actualité. D’ailleurs, la fabrication de nanoparticules métalliques (NPM) uniformes se fait principalement par synthèse colloïdale particulièrement par « seed mediated growth ». En revanche, cette méthode présente toujours certaines limitations dans le temps de préparation et la contrôle de taille et de forme. Dans ce contexte, nous avons, dans cette thèse, développé une nouvelle méthode de fabrication de nanoparticules métalliques (NPM) de différentes formes. Le principe consiste à structurer un polymère (PMMA) sous forme d’un film nanoporeux et d’utiliser les nanopores comme réacteur de synthèse de NPM. C'est ainsi que l’objectif de cette thèse était d’exploiter la méthode de fabrication ainsi proposée afin d’élaborer de nouveaux nano-capteurs de détection basés sur le SERS. Les travaux dans le cadre de cette thèse ont été réparties sur trois grands volets : Le premier consiste à étudier le mécanisme de synthèse afin d’optimiser le processus de formation des structures métalliques uniformes. Le 2ème vise à faire évoluer la forme des NPM en jouant sur les paramètres de synthèse. En parallèle à ces deux volets, une tâche importante a été consacrée à l’analyse morphologique en utilisant les techniques d’analyses structurales, et à la détermination et la modélisation des réponses optiques de ces NPMs notamment par la technique d’ellipsométrie spectroscopique / Controlled synthesis of metallic nanoparticles (MNPs), according to particular morphologies and dimensions, is an interdisciplinary field of research because of the new, varied, rich and complex physical properties of MNPs. These properties are mainly governed by the collective oscillations of conduction electrons called plasmons. This phenomenon is optically reflected by the sensitivity of the MNPs to the change in the surrounding refractive index and by the shift of their plasmon resonance band. This feature, according to the morphology of MNPs, is used in fairly modern applications such as cancer phototherapy and the development of the ultrasensitive sensors based on Surface Plasmon Resonance (SPR) or Surface Enhanced Raman Spectroscopy (SERS). The sensitivity of MNPs as sensors is not only directly related to the chemical and crystalline nature of the metal but also to their ability to adsorb target molecules, absorb and/or confine and enhance incident light. This last property is generally more remarkable as the distance separating the MNPs is small. Thus, the control of the size, shape and density of the MNPs is of major interest. Therefore, the development of new synthesis methods of MNPs is still relevant. Moreover, the fabrication of uniform metallic nanoparticles is mainly achieved by colloidal synthesis particularly by "seed mediated growth". On the other hand, this method always has certain limitations in the preparation time and the control of the size and shape. In this context, we have, in this thesis, developed a new fabrication method of MNPs of different shapes. The idea is to structure a polymer (PMMA) in the form of a nanoporous film and to use the nanopores as synthesis reactor for MNPs. Thus, the objective of this thesis was to investigate the proposed synthesis method in order to develop new detection nanosensors based on SERS phenomenon. The work in this thesis has been divided into three main parts: the first is to study the synthesis mechanism in order to optimize the formation process of uniform metallic structures. The second aims to change the shape of the MNPs by playing on the parameters of synthesis. In parallel with these two aspects, an important task was devoted to morphological analysis using structural analysis techniques, and to the determination and the modelling of the optical responses of these MNPs particularly by the technique of spectroscopic ellipsometry

Au cours de ma thèse, j'ai développé un procédé de fabrication spécifique capable de produire un biocapteur qui combine deux techniques de biodétection différentes, la réponse plasmonique basée sur la résonance de plasmon de surface localisée (LSPR) et la réponse électrochimique. Les méthodes et les résultats qui sont présentés dans ce manuscrit ont été définis pour converger vers un dispositif fluidique unique combinant ces deux approches de détection différentes. Afin de trouver la configuration permettant l'excitation des résonances plasmoniques, la géométrie des nanocavités MIM (métal/isolant/métal) en réseau de lignes interdigitées a été optimisée par des simulations électromagnétiques. La fabrication par nanoimpression douce assistée UV (SoftUV-NIL) a été optimisée et, finalement, la caractérisation optique de ces nanocavités a été comparée avec succès aux simulations théoriques. Parallèlement à la réalisation de ce dispositif nanostructuré, des dispositifs électrochimiques fluidiques plus simples qui intègrent des microélectrodes classiques ont également été développés. L'objectif était d'abord de développer une chimie innovante pour le couple « biotine/streptavidine » et de comprendre ensuite comment les paramètres fluidiques peuvent affecter l'efficacité de capture des biomolécules. Ce manuscrit se termine par une discussion sur le rôle des paramètres fluidiques concernant l’efficacité de la biodétection sur la base de la théorie de Squires. / During my thesis, I worked on the development of a specific fabrication process able to produce a device that combines two different biodetection techniques, plasmonic response based on Localized Surface Plasmon Resonance (LSPR) and electrochemical response. Methods and results that are presented in this manuscript were defined to converge towards a unique fluidic device combining these two different sensing approaches. This device integrates interdigitated array of MIM nanocavities. In order to find the easier working configuration allowing the excitation of plasmonic resonances, their geometry has been optimized through electromagnetic simulations. The fabrication of these dual devices has been optimized based on Soft-UV NIL and, finally, optical characterization of these nanocavities has been successfully compared with theoretical simulations. In parallel to this challenging goal, simpler fluidic electrochemical devices that integrate conventional microelectrodes have also been developed. The goal was first to develop an innovative chemistry for the couple biotin/streptavidin and secondly to learn how fluidic parameters can affect the capture efficiency of molecules. This manuscript ends with a discussion on the role of the fluidic parameters on the biodetection efficiency based on the theory of Squires.

Afin de poursuivre la réduction d'échelle des transistors MOS, l'industrie des semiconducteurs a su anticiper les limitations de la miniaturisation par l'introduction de nouveaux matériaux ou de nouvelles architectures. L'avènement des structures à triples grilles (FinFET) a permis de maitriser les effets canaux courts et poursuivre les efforts de miniaturisation (nœud technologique 14 nm en 2014). Le cas ultime pour le contrôle électrostatique de la grille sur le canal est donné par une grille entourant totalement le canal du dispositif. A cet effet, un transistor à nanofil à grille entourante est considéré comme la structure la plus adaptée pour les nœuds technologiques en dessous de 7 nm. Au cours de cette thèse, un procédé de réalisation large échelle de transistors MOSFET miniaturisés à base de nanofils verticaux en silicium a été développé. Tout d'abord, les nanofils verticaux ont été réalisés par une approche descendante via le transfert par gravure d'un masque de résine en Hydrogène Silsesquioxane (HSQ), réalisé par lithographie électronique à basse tension d'accélération. Une stratégie de dessin inédite dite "en étoile " a été développée pour définir des nanofils parfaitement circulaires. Les nanofils en Si sont obtenus par gravure plasma puis amincis par oxydation humide sacrificielle. Ce procédé permet d'obtenir des nanofils verticaux en Si avec des parois parfaitement anisotropes, une parfaite reproductibilité et un rendement maximal. L'implémentation des MOSFETs sur les réseaux nanofils a été effectuée par l'ingénierie successive de couches minces nanométriques (conductrices et diélectriques). Dans ce cadre, un procédé innovant de réalisation de couches d'isolations en HSQ par gravure chimique contrôlée a démontré une excellente planéité associée à une rugosité de surface inférieure à 2 nm. Enfin, un procédé utilisant la photolithographie UV conventionnelle a été développé pour réaliser le transistor de longueur de grille nanométrique. Ces dispositifs ont démontré d'excellentes performances électriques avec des courants de conduction supérieurs à 600 µA/µm et une excellente maîtrise des effets de canaux courts (pente sous le seuil de 95 mV/dec et DIBL à 25 mV/V) malgré l'extrême miniaturisation de la longueur de grille (15 nm). Enfin, nous présentons une première preuve de concept d'un inverseur CMOS à base de cette technologie à nanofils verticaux. / In order to further downscaling of the MOS transistors, the semiconductor industry has anticipated the limitations of miniaturization by the introduction of new materials and new architectures. The advent of triple gate structures (FinFET) allowed mastering the short channel effects and further miniaturization efforts (14 nm technology node in 2014). The ultimate case to the electrostatic control of the gate on the channel is given by a gate completely surrounding the device channel. For this purpose, Gate All Around (GAA) nanowire transistor is considered as the most suitable structure for technology nodes below 7 nm. In this thesis, a large scale process for the realization of miniaturized MOSFETs based on vertical silicon nanowires has been developed. Firstly, the vertical nanowires were made by a top down approach by the transfer by etching of hard mask made of Hydrogen silsesquioxane (HSQ) resist created at low voltage electron beam lithography. An original design strategy called "star" was developed to define perfectly circular nanowires. Si nanowires are obtained by plasma etching then thinned by sacrificial wet oxidation. This method allows obtaining vertical Si nanowires with perfectly anisotropic walls, a perfect reproducibility and a maximum yield. The implementation of the MOSFETs on the nanowire network was done by successive engineering of nanoscale thin films (conductive and dielectric). In this context, an innovative process for producing insulation layers in HSQ by controlled chemical etching showed excellent flatness associated with surface roughness of less than 2 nm. Finally, a method using conventional UV photolithography has been developed to achieve the nanometer gate length transistor. These devices have demonstrated excellent electrical performances with conduction currents superior than 600 µA/µm and excellent control of short channel effects (subthreshold slope of 95 mV/dec and DIBL of 25 mV/V) despite extreme miniaturization of the gate length (15 nm). Finally, we present a first proof of concept of a CMOS inverter based on vertical nanowires technology.

First proposed in the late 1990's, a nanomechanical electron shuttle is a device where an electrically isolated island moves a definite number of electrons between two leads, producing a current that is directly related to the number of electrons moved in a cycle and to the vibration frequency of the island. Since nanomechanical structures can have very well defined vibration frequencies, a device of this type is useful as, among other things, a current standard for metrology. The experimental shuttle implementations to date have had large island-lead spacings, which has limited their performance. The work presented here takes the first steps towards the fabrication of a nanomechanical electron shuttle using the process of electromigration to define very small lead-island gaps with conductivity on the order of the conductance quantum G_0=2e^2/h. These small gaps, coupled with the high vibration frequencies achievable with nanostructures, will allow investigation deeper into the realm of quantum effects. In this work, the fabrication steps for the creation of these devices were developed. Electromigration of a single junction was successfully achieved to the 10--100\,k\ohm range. The simultaneous and symmetric electromigration of two junctions, as required for the shuttle, has not yet been achieved. The development of a fast electromigration cut-off circuit, however, gives hope that double-breaking success will be achieved soon. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2010-01-28 23:01:15.735