Chalcogenide based Phase Change Materials are currently of great technological interest in the growing field of optoelectronics. Ge₂Sb₂Te₅ (GST) is the most widely studied phase change material, and it has been commercially used in both optical and electronic data storage applications, due to its ability to switch between two different atomic configurations, at high speed and with low power consumption, as well as its high optical and electrical contrast between amorphous and crystalline states. Despite its well-known optical and electrical properties, the operation in combination of optical and electrical domains has not yet been fully investigated. This work studies the operation of GST nano-devices exposed to a combination of optical and electrical stimuli or mixed mode by asking, is it possible to electrically measure an optically induced phase change, or vice versa? If so, how do the optical and electrical responses relate to each other, and is it possible to operate GST with a combination of optical and electrical signals? What are the technical constraints that need to be considered in order to fabricate GST devices that could be operated either optically or electrically? In order to answer these questions, experiments that characterized the optical and electrical responses of GST based nano-devices were performed. It was found that different crystallization mechanisms may have influence in the response, and that the thermal and optical design characteristics of the device play a key role in its operation. Finally a proof of principle, of an opto-electonic memory device that can be read electrically, reset optically and write electrically, is presented. This opens up possibilities for the development of new opto-eloectronic applications such as non-volatile interfaces between future photonics and electronics, high speed optical communication detectors, high speed cameras, artificial retinas and many more.

Nanomagnetic devices have been projected as an alternative to transistor-based switching devices due to their non-volatility and potentially superior energy-efficiency. The energy efficiency is enhanced by the use of straintronics which involves the application of a voltage to a piezoelectric layer to generate a strain which is ultimately transferred to an elastically coupled magnetostrictive nanomaget, causing magnetization rotation. The low energy dissipation and non-volatility characteristics make straintronic nanomagnets very attractive for both Boolean and non-Boolean computing applications. There was relatively little research on straintronic switching in devices built with real nanomagnets that invariably have defects and imperfections, or their adaptation to non-Boolean computing, both of which have been studied in this work. Detailed studies of the effects of nanomagnet material fabrication defects and surface roughness variation (found in real nanomagnets) on the switching process and ultimately device performance of those switches have been performed theoretically. The results of these studies place the viability of straintronics logic (Boolean) and/or memory in question. With a view to analog computing and signal processing, analog spin wave based device operation has been evaluated in the presence of defects and it was found that defects impact their performance, which can be a major concern for the spin wave based device community. Additionally, the design challenge for low barrier nanomagnet which is the building block of binary stochastic neurons based probabilistic computing device in case of real nanomagnets has also been investigated. This study also cast some doubt on the efficacy of probabilistic computing devices. Fortunately, there are some non-Boolean applications based on the collective action of array of nanomagnets which are very forgiving of material defects. One example is image processing using dipole coupled nanomagnets which is studied here and it showed promising result for noise correction and edge enhancement of corrupted pixels in an image. Moreover, a single magneto tunnel junction based microwave oscillator was proposed for the first time and theoretical simulations showed that it is capable of better performance compared to traditional microwave oscillators. The experimental part of this work dealt with spin wave modes excited by surface acoustic waves, studied with time resolved magneto optic Kerr effect (TR-MOKE). New hybrid spin wave modes were observed for the first time. An experiment was carried out to emulate simulated annealing in a system of dipole coupled magnetostrictive nanomagnets where strain served as the simulated annealing agent. This was a promising outcome and it is the first demonstration of the hardware variant of simulated annealing of a many body system based on magnetostrictive nanomagnets. Finally, a giant spin Hall effect actuated surface acoustic wave antenna was demonstrated experimentally. This is the first observation of photon to phonon conversion using spin-orbit torque and although the observed conversion efficiency was poor (1%), it opened the pathway for a new acoustic radiator. These studies complement past work done in the area of straintronics.

In this thesis, the tunneling between individual atomic layers in structures of Bi2Sr2CaCu2O8+x based high-temperature superconductors are experimentally studied employing the intrinsic Josephson effect. A special attention is paid to the fabrication of small mesa structures using micro and nanofabrication techniques. In the first part of the thesis, the periodic Fraunhofer-like modulation of the critical current of the junctions as a function of in-plane magnetic field is investigated. A transition from a modulation with a half flux quantum to a flux quantum periodicity is demonstrated with increasing field and decreasing junction length. It is interpreted in terms of the transformation of the static fluxon lattice of stacked, strongly coupled intrinsic Josephson junctions and compared with theoretical predictions. A fluxon phase diagram is constructed.Numerical simulations have been carried out to complement the experimental data. In the second part of the thesis, different resonant phenomena are studied in the dynamic flux-flow state at high magnetic fields, including Eck-resonances and Fiske steps. Different resonant modes and their velocities, including superluminal modes, are identified. In the third part, different experiments attempting to detect radiation from small mesa structures using different setups based on hot-electron bolometer mixers and calorimeters are described. No distinct radiation with emission powers higher than about 500pW could be detected. Furthermore, the interaction with external GHz-radiation is studied. Resonances attributed to an induced flux-flow are observed, and the reflectivity of the sample can be tuned by switching mesas between the superconducting and quasiparticle state. In the last part, the resistive switching of mesas at high bias is studied. It is attributed to a persistent electrical doping of the crystal. Superconducting properties such as the critical current and temperature and the tunneling spectra are analyzed at different doping states of the same sample. The dynamics of the doping is studied, and attributed to two mechanisms; a charge-transfer effect and oxygen reordering

Le champ d'application des microsystèmes n'a cessé de s'élargir pendant les quinze dernières années en particulier vers la communication ou vers les biotechnologies. Pour augmenter les fonctionnalités des microsystèmes, l'utilisation de nano-objets semble devenir une voie incontournable, mais qui butte souvent sur des problèmes mes de manipulation spatiale visant à les intégrer dans une architecture fonctionnelle. Pour résoudre ces problèmes d'intégration, l'utilisation de phénomènes d'assemblage dirigé, c'est à dire des phénomènes physiques permettant de manipuler collectivement des nano-objets semble très prometteuse. Dans ce contexte, l'objectif de notre thèse a été de concevoir des outils fluidiques innovants capables de réaliser des opérations de manipulation spatiale ou conformationnelle de nano-objets ou de molécules. Il s'agit d'une recherche pluridisciplinaire à la frontière entre la micro- et nano-fabrication, la micro- et nano-fluidique, la biologie moléculaire, l'imagerie de molécules individuelles, et la biophysique. La thèse est composée de deux projets assez indépendants : une étude de nanofluidique pour le contrôle conformationnel de chromosomes issus de cellules vivantes, et un travail de microfluidique sur un phénomène d'assemblage spontané sur gel hydrophile. Dans un premier temps, nous décrivons un procédé de fabrication d'hydrogels structurés, et nous montrons que ces hydrogels constituent un support efficace pour organiser spatialement des nano-objets. Ce phénomène d'organisation est spontané, et il se produit lors du séchage du liquide. Nous avons donc voulu comprendre les mécanismes fluidiques ayant lieu au cours du séchage en utilisant des traceurs fluorescents. Nous identifions plusieurs phénomènes expliquant les phénomènes d'organisation spatiale de particules, et nous proposons des applications pour ce procédé innovant. Grâce aux dispositifs nanofluidiques que nous avons fabriqués, nous menons des expériences de manipula tion de molécules d'ADN individuelles en milieu confiné. Nous analysons le comportement de l'ADN - son élongation, sa mobilité, l'effet de la salinité, le rôle du matériau dans lesquels le nanocanaux sont inscrits - en utilisant deux modes d'actionnement, à savoir l'électrophorèse et l'hydrodynamique, et nous montrons, pour la première fois, l'intérêt de l'hydrodynamique pour la manipulation d'ADN dans des nanostructures. Nous proposons enfin quelques applications pour ce procédé de manipulation d'ADN innovant.

Cette thèse présente une étude des propriétés de transport à basses températures de matériaux hybrides composés de nano-clusters de métaux supraconducteurs (Sn et Pb) auto-assemblés à la surface d'une feuille de graphène. L'auto-assemblage du métal réalise un réseau bi-dimensionnel désordonné de jonctions Josephson. La caractérisation des propriétés supraconductrices révèle une transition de type 'BKT' avec une température de transition dépendant de la morphologie de la surface. Les propriétés supraconductrices de ce système sont fortement influencées par la grille arrière, qui contrôle la résistance dans l'état normal du graphène. Le résultat le plus marquant de cette thèse a été obtenu en utilisant du graphène désordonné. La présence de défauts structuraux dans la maille de graphène induit un régime de localisation forte à basses températures. En faisant varier le voltage de grille, la résistance de tels échantillons peut varier de 3 ordres de grandeurs. Cette grande dynamique a été mise à contribution pour la réalisation d'une transition de phase supraconducteur-isolant dans des échantillons décorés à l'étain. L'étude de cette transition de phase quantique révèle un comportement de type percolatif et une résistivité universelle prédite par la théorie à la transition. Enfin, un travail préliminaire visant à réaliser des résonateurs mécaniques supraconducteurs à l'aide des ces matériaux hybrides est également présenté.

Cette thèse présente une étude des propriétés de transport à basses températures de matériaux hybrides composés de nano-clusters de métaux supraconducteurs (Sn et Pb) auto-assemblés à la surface d'une feuille de graphène. L'auto-assemblage du métal réalise un réseau bi-dimensionnel désordonné de jonctions Josephson. La caractérisation des propriétés supraconductrices révèle une transition de type 'BKT' avec une température de transition dépendant de la morphologie de la surface. Les propriétés supraconductrices de ce système sont fortement influencées par la grille arrière, qui contrôle la résistance dans l'état normal du graphène. Le résultat le plus marquant de cette thèse a été obtenu en utilisant du graphène désordonné. La présence de défauts structuraux dans la maille de graphène induit un régime de localisation forte à basses températures. En faisant varier le voltage de grille, la résistance de tels échantillons peut varier de 3 ordres de grandeurs. Cette grande dynamique a été mise à contribution pour la réalisation d'une transition de phase supraconducteur-isolant dans des échantillons décorés à l'étain. L'étude de cette transition de phase quantique révèle un comportement de type percolatif et une résistivité universelle prédite par la théorie à la transition. Enfin, un travail préliminaire visant à réaliser des résonateurs mécaniques supraconducteurs à l'aide des ces matériaux hybrides est également présenté. / This thesis presents a study of the low temperature transport properties of hybrid materials made of superconducting metals (Sn and Pb) nano-clusters self-assembled onto the surface of a graphene sheet. The self-assembly realizes a two-dimensional disordered array of Josephson junctions. Characterization of the superconducting properties reveals a transition of the 'BKT' kind, with a transition temperature that depends on surface morphology. The superconducting properties are strongly affected by the gate voltage, which controls the normal state resistance of the graphene sheet. The main result of this thesis was obtained using disordered graphene. The presence of structural defects in the graphene lattice induces a regime of strong localization at low temperatures. Upon varying the gate voltage, the resistance of such samples can change by 3 orders of magnitude. Taking advantage of the large dynamics offered by the gate voltage, we have induced a superconductor-insulator transition in Sn-decorated samples. The study of that quantum phase transition reveals a percolating behavior near the threshold and the universal value of resistivity predicted by theory at the transition. Finally, a preliminary work aiming at using such an hybrid material to realize superconducting nano-electro-mechanical resonators is presented.

<p>  </p> <p>The development of the semiconductor industry is encountering a giant leap recently as Moorse’s is extended to the next levels. Advanced nanomanufacturing technology is the major challenge in the way. Higher resolution down to a few nanometers as well as higher throughput is always the key. As the optical lithography determines the feature size, the photomask is still in need of a low-cost and high resolution maskless patterning tool. In another aspect, the growing information allows the generation and storage of data at ever faster rates, which has led to the era of big data reaching a heroic amount of 7 zettabytes of total data in 2020. Future growth requires the total shipment of data storage capacity to double roughly every two years or less. For the future generation of magnetic data storage, the bit patterned medium (BPM) in combination with the current heat assisted magnetic recording (HAMR) is expected to increase the areal storage capacity by another order of magnitude by physically isolating magnetic bits at the nanoscale. Electron beam lithography (EBL) as a universal maskless lithography technique shows great resolution but has a high tool cost and low process throughput. Scanning probe lithography (SPL) is another family of nanoscale patterning techniques with low tool cost but the practical throughput is still limited. For example, dip pen nanolithography utilizes an AFM probe as a writing pen in direct patterning, but the ink delivery is limited by the rate of ink’s capillary transport. Other SPLs such as thermal probes with capabilities of 3D fabrication and surface oxidation via chemical reactions are all facing similar limitations in throughput. One way of breaking this limitation is to use parallel writing with millions of probes which also faces uniformity problems. </p> <p>In this Ph.D. dissertation, we report our Surfing Scanning Probe lithography (SSPL) method which can boost the scanning speed of SPL by several orders of magnitudes at a low cost by using a hydro-aero-dynamic scanning scheme. We use a homemade patterning head to continuously scan over a partially-wet spinning substrate at a linear speed of meters per second. The head carries several metallic tips which emit electrons and induce electrochemical reactions inside a gap of 10 nm scale. We use a liquid phase precursor and deliver it using the near-field electrospinning method and microfluid structures during the fast patterning. The best linewidth demonstrated is about 15 nm in full-width half maximum (FWHM) which can be further improved using smaller scanning gaps and sharp probe tips. Besides direct writing with a liquid precursor, SSPL can work with gas precursors as well enabled by nano plasma. The rate of material deposition is much high than conventional SPL. The SSPL system is a low-cost nanopatterning technology to produce patterns at high throughput and high resolution.</p>