<p>The ferrimagnetic electrical insulator yttrium iron garnet (YIG) has been proved a promising magnonic platform that allows for a variety of application within microwave fre- quency range. This dissertation focuses on the development of novel spin wave resonators and filters for next-generation radio frequency technology.</p> <p>Chapter 1 begins with an introduction to modern radio frequency communication tech- nology and motivation of our research on novel radio frequency devices.</p> <p>Chapter 2 discusses about the properties of yttrium iron garnet (YIG) thin film platform and theory of magnetostatic waves (MSW) within the magnetic thin film system. Three different types of magnetostatic wave modes, known as magnetostatic forward volume wave (MSFVW), magnetostatic backward volume waves (MSBVW) and magnetostatic surface wave (MSSW), are illustrated in this section. They have very distinct dispersion relations and require different transduction technology, which leads to disparate designs for devices utilizing different modes. The damping mechanism and linewidth of the magnetostatic modes will also be discussed in this chapter.</p> <p>Chapter 3 will showcase a new YIG-on-Si platform created using novel YIG bonding technology and the first ever on-chip MSFVW hairpin resonator on the YIG-on-Si platform. In the first part, we would like to show finite element analysis of YIG-on-Si MSFVW hairpin resonator and prove the capability of the hairpin transducer incorporated with YIG thin film to yield lower self-inductance and stronger excitation field. These unique properties are beneficial for generating high coupling between magnon and microwave domains. In the following sections, the bonding technology essential for creation of YIG-on-Si platform and key fabrication technology of hairpin devices are explained in detailed. With well defined fabrication process established, we will demonstrate that the hairpin magnetostatic wave resonator obtained through the process is magnetically tunable with a high coupling efficiency over 50%. An out-of-plane Z-directional tunable magnetic field results in forward volume spin-wave resonance with frequency in the 5G band. This technology enables us to build on-chip devices of desirable high coupling and magnetic tuning on the new YIG-on-Insulator platform and provides possibility of magnetic tuning and band-pass filter at radio-frequency range.</p> <p>Chapter 4 demonstrates a planar monolithic yttrium iron garnet (YIG) Chebyshev bandstop filter on traditional gadolinium gallium garnet (GGG) substrate with tunable frequency, low insertion loss and high rejection. This filter is created in YIG micro-machining technol- ogy that allows direct placement of metal transducers on YIG for strong spin-wave coupling. With an out-of-plane 3900 Oe bias field, the bandstop filter exhibits 55 dB maximum stop- band rejection at a center frequency of 6 GHz, with 2 dB passband insertion loss and 37.8 dBm passband <strong>IIP3</strong>. By applying different bias fields, the stopband center frequency is tuned from 4 GHz to 8 GHz while maintaining more than 30 dB rejection. Incorporated with proper design of tunable compact electromagnet, this new filter design can provide attenuation of spurs appearing across the 5G and X-band spectrum.</p> <p>In chapter 5, we will explore the properties of YIG thin-film materials in depth. Both YIG-on-Si and YIG-on-GGG platform under different conditions will be examined. Results of X-ray diffraction (XRD), ferromagnetic resonance (FMR), scanning tunneling microscope (STM) on the YIG thin films will be presented. Those results will cast light onto the study of limiting factors of our YIG-on-Si and YIG-on-GGG devices.</p>

Structural biology has become an important part of researching various diseases and drug development. In this thesis, I provide details on how I worked with approaches to structural characterization of a heteromeric GABA(A)R. These pentameric ligand gated ion channels take part in regulating inhibition of action potentials in nerve cells by allowing the passage of Cl- ions when bound by gamma-aminobutyric acid (GABA). They are formed by the assembly of five subunits which can be of various different types, denoted by greek letters and a number. Much is still unknown about how GABA and several other ligands bind to these ion channels and how that impacts function. Obtaining a structure of these proteins can aid in closing those knowledge gaps. It is reasonable to screen the proteins you have before you study their structures by Cryo-EM in order to get the best result, a methodology for which is described here. I have followed this methodology to screen two heteromeric GABA$_A$R that we wish to determine the structure of, alpha 5 beta 3 and rho 1 gamma 2. Neither of the combinations of genes we used to express these proteins proved to produce the desired fully assembled heteromeric protein. In the case of alpha 5 beta 3, we only witnessed building blocks, with no fully assembled channels. In rho 1 gamma 2, we instead only witnessed fully formed homomers of the rho 1 subunit. These findings then exclude the gene constructs used from further structural study, and the methodology described will inform the next steps to be taken. / Strukturbiologi har blivit en viktig del av forskningen kring många sjukdomar samt utveckling av läkemedel. I denna uppsats delger jag hur jag arbetat med metoder för strukturell karakterisering av en heteromerisk GABA(A)R. Dessa pentameriska ligandstyrda jonkanaler deltar i regleringen av hämning av aktionspotentialer i nervceller genom att tillåta passagen av Cl- joner när gamma-aminosmörsyra (GABA) binder. Dessa består av fem subenheter som kan vara en av flera olika typer, vilka anges med en grekisk bokstav och en siffra. Mycket om hur GABA och andra ligander binder till dessa jonkanaler och hur det påverkar dess funktion är fortfarande okänt. Att hitta en struktur av dessa proteiner kan hjälpa oss att stänga kunskapsgapen. Det är klokt att undersöka om genen man ska använda för att uttrycka det sökta proteinet ger det man söker innan man sen börjar studera strukturen. Jag har beskrivit en metodologi för detta och följt den för två heteromeriska proteiner, alpha 5 beta 3 och rho 1 gamma 2. Ingen av kombinationerna av gener vi använt för att uttrycka dessa proteiner har producerat de sökta, fullt ihoppbyggda proteinerna. I fallet för alpha 5 \beta 3 så ser vi endast byggstenar och inga kompletta proteiner, och för rho 1 gamma 2 så ser vi endast homomeriska proteiner av rho 1. Dessa slutsatser exkluderar de genkonstruktioner vi använt från vidare strukturella studier, och stegen som bör tas härnäst beskrivs av den använda metodologin.

La supraconductivité dans la famille des composés de type fermions lourds tel le CeCoIn5 se développe à proximité d’une instabilité antiferromagnétique. La proximité de cette instabi- lité indique un point quantique critique (anglais pour ”quantum critical point” QCP) entre la phase antiferromagnétique et un liquide de Fermi. À ce point, les deux états fondamentaux du système sont en compétition et peuvent être perturbés par une variation de la pression ou de la composition chimique. Dans cette proposition, nous étudions la réciprocité entre les deux méthodes de perturbation du point quantique critique. Pour ce faire, on change la composition chimique du CeCoIn5 en dopant le cristal avec des atomes d’ytterbium qui prennent la place du cérium dans la structure. La substitution de certains atomes de cérium par de l’ytterbium est équivalent électroniquement à enlever un électron de la couche 4f car l’ytterbium est bivalent dans la structure CeCoIn5 . Ainsi, on détruit des moments magné- tiques dans le réseau fortement corrélé de centres de Kondo et pousse le matériau vers la phase antiferromagnétique. Dans la même optique, on utilise un accélérateur de particules pour implanter des atomes d’hélium dans la maille du cristal. Les atomes d’hélium agissent comme une source de pression négative qui dilatent le réseau et réduisent la cohérence entre certaines quasi-particules de Kondo. On propose alors que cette implantation pourrait induire l’ordre antiferromagnétique puisqu’elle favorise l’interaction magnétique longue portée. Dans un premier ordre, on a dopé les échantillons de CeCoIn5 dopé à l'Yb avec une concentration de 5%, 10% et 15%. Tel qu’attendu, suite aux mesures de la chaleur spécifique en fonction de la température, on s’aperçoit que la valeur de la température de transition de phase supraconductrice diminue lorsqu’on augmente le dopage dans le monocristal. On montre ainsi la dépendance entre la concentration de dopant dans le cristal et la destruction inhomogène de l’état corrélé. Lorsqu’on remplace des électrons de l’orbitale 4f par des trous de cette bande, on détruit la cohérence entre les centres de Kondo qui induit la supraconductivité. Cette variation chimique peut être utilisée comme un paramètre de réglage qui favorise le régime de l’interaction magnétique près du QCP. Similairement, suite à une implantation d’atomes d’hélium de 0.1%, 0.5% et 1% des mailles dans les premiers 15 micromètre de CeCoIn5 , on constate que la dilatation du réseau réduit linéairement l’intéraction globale du régime fortement corrélé entre les singulets de Kondo. Cependant, la cohérence entre les centres de Kondo est plus difficile à obtenir, ce qui diminue la température critique (Tc) de la transition de phase supraconductrice. On associe cette diminution de Tc proche d’un QCP à la suppression inhomogène du régime liquide de Fermi. Alors, l’application d’une pression négative par implantation d’hélium est considérée comme un paramètre de réglage qui avantage l’interaction magnétique longue portée et conduit le cristal vers l’ordre AFM. / Superconductivity in the family of heavy fermion compounds such as CeCoIn5 develops near an antiferromagnetic instability. The proximity of this instability indicates a quantum critical point (QCP) between the antiferromagnetic phase and a Fermi liquid ground state. At such a point, the two ground states of the system are in competition and applying pressure or changeing the chemical composition moves the system away from the QCP. In this work, we study the reciprocity between the two methods of perturbation of the QCP. In this sense, the chemical composition of the CeCoIn5 is changed by doping the system with ytterbium atoms, which replace the cerium. The substitution of cerium which is trivalent and carries a magnetic moment atoms by the bivalent ytterbium is electronically and non-magnetic electron of the shell 4f by a hole of the same orbital and removing a magnetic moment. Thus, we destroy magnetic moments causing the Kondo coherence and push the material towards the antiferromagnetic phase. In the same vein, an accelerator is used to implant helium atoms in the lattice of the crystal. Helium atoms act as a source of negative pressure which expands the lattice and which destroys the coherence between certain Kondo singlets. It is then proposed that this implantation should eventually induce antiferromagnetic order since this is favoring the long-range magnetic interaction. First, Ce1−xYbxCoIn5 samples were doped with an Yb concentration of x = 5%, 10% and 15%. As expected, following the measurements of the specific heat as a function of temperature, it is found that the value of the temperature of the superconducting phase transition (Tc) decreases when the level of doping increases in the single crystal. Thus, we conclude that the more electrons in the 4f orbital are replaced by holes of this band, the more we destroy the coherence between the Kondo center which induces superconductivity We also show that this inhomogeneous destruction of the correlated state is linear with the concentration of induced holes in the crystal. we conclude that the more electrons in the 4f orbital are replaced by holes of this band, the more we destroy the coherence between the Kondo center which induces superconductivity. In this sense, this chemical variation used as a tunning parameter favors the magnetic state near the QCP. Similarly, following a helium atom implantation of 0.1%, 0.5% and 1% of the lattices in the first 15 μm of CeCoIn5 , we find that lattice expansion linearly decreases the correlation between Kondo singlets. Thus, the coherence between Kondo centers is more difficult to achieve, which decreases the critical temperature (Tc) towards the superconducting phase transition. This linear decrease of Tc close to a QCP is associated to the suppression of the Fermi liquid regime and thus is expected to lea the crystal to the AFM order. Then, the application of a negative pressure by helium implantation can be considered as a tunning parameter which benefits the long-range magnetic interaction

Anderson localization occurs when an otherwise conductive solid becomes insulatingdue to a sufficiently large degree of disorder in the medium. The electron band energy(as a function of disorder) at which this transition between extended and localizedelectron states occur is called the mobility edge (ME) and is energy-dependent only in3-dimensional systems. In lower dimensional systems, energy-independent ME (allstates localized or all extended) has been demonstrated by replacing disorder withquasi-periodic potential. However, recent theoretical findings indicate that neitherdisorder nor quasi-periodic potential is necessary for a material to exhibit electronlocalization and existence of energy-dependent pseudo ME at finite system size.In this thesis work, we use light in coupled silicon nitride waveguides to simulatesingle-particle transport of a solid-state medium and investigate the coexistence ofdelocalized and localized states in disorder-free photonic lattices of finite systemsize. This was achieved by implementing a simulated linearly increasing electricpotential on even-numbered sites by varying the refractive index of the wave guide(ch. 3). Through our experimental setup, we successfully achieved a coexistence oflocalized and delocalized states, where the degree of localization varies depending onthe strength of the applied electric field.The findings have implications for the field of quantum technology, whereunderstanding and controlling quantum states is crucial. The ability to achievelocalization in the absence of disorder opens new possibilities for designing andengineering photonic devices for quantum information processing tasks. / Anderson-lokalisering uppstår när ett annars ledande fast material blir isolerande pågrund av en tillräckligt stor grad av oordning i mediet. Elektronbandsenergin (som enfunktion av oordning) vid vilken denna övergång mellan förlängda och lokaliseradeelektrontillstånd sker kallas mobilitetskanten (ME) och är energiberoende endasti 3-dimensionella system. I lägre dimensionella system har energioberoende ME(alla tillstånd lokaliserade eller alla förlängda) påvisats genom att ersätta oordningmed kvasi-periodisk spänning. Nya teoretiska fynd indikerar dock att varkenoordning eller kvasi-periodisk spänning är nödvändig för att ett material ska uppvisaelektronlokalisering och förekomsten av energiberoende pseudo-ME för system avfinita storlekar.I detta examensarbete använder vi ljus i kopplade vågledare av kiselnitrid föratt simulera transport av en partikel i ett fast tillståndsmedium och undersökersamexistensen av icke-lokaliserade och lokaliserade tillstånd i finita system utanoordning med fotoniska gitter. Detta uppnåddes genom att implementera ensimulerad linjärt ökande elektrisk potential på varje jämnt numrerat gitterläge platsgenom att öka vågledarbredderna och noll elektrisk spänning på varje udda. Genomvårt experimentella upplägg lyckades vi uppnå lokaliserade och förlängda tillstånd, därgraden av lokaliseringen varierade beroende på styrkan av det tillämpade elektriskafältet.Fynden har implikationer för kvantteknologi, där förståelse och kontroll avkvanttillstånd är avgörande. Förmågan att uppnå lokalisering i frånvaro avoordning öppnar nya möjligheter för att designa och konstruera fotoniska enheter förkvantinformationsprocesser.

Metamaterials are artificially designed materials with desired electromagneticresponses for advanced wave manipulation. Their key constituent is often somenoble metal, thanks to its well localized plasmonic effects with highextinction cross section. In this project, a metamaterial based onmetal-insulator-metal (MIM) structure is investigated to create a compactplanar reflector which mimics the function of a parabolic mirror. In such ametamaterial, each MIM unit is essentially a sub-wavelength resonator whichexhibits magnetic-dipole resonance. To achieve focusing effect, phase shift onreflected wave by each MIM unit upon a plane-wave incidence is calculatedrigorously through finite-element method. By carefully selecting unitgeometries and thereby introducing a phase gradient along the reflector plane,one can control propagation direction of reflected wave at each reflectorposition. The principle can be explained in terms of either ray-optics theoryor generalized Snell’s law. As a particular demonstration, we have designed inthe thesis a planar reflector consisting of eleven MIM units with a totaldevice width of 5.5 µm. FEM simulation showed that the reflector focuses lightat 1.2 µm wavelength with a nominal focus length of 6 µm. Such compactmetamaterial devices can be potentially fabricated on chips for sensing andtelecom applications, circumventing many inconveniences of includingconventional lenses in an optical system. / Metamaterial är artificiellt konstruerade material med vissa önskadeelektromagnetiska egenskaper, vilket kan utnyttjas för avancerad styrning avelektromagetisk vågutbredning. Metamaterialet som undersöks i denna rapportär baserad på en metall-isolator-metall (MIM) struktur, denna strukturkommer användas för konstruktion av en platt parabolisk reflektor. Vilket isin tur består av en serie MIM-strukturer med varierande storlekar. VarjeMIM-struktur är i princip en resonator med en storleksordning mycket mindreän våglängden och ger upphov till en magnetisk resonans. För att sedan uppnåfokus genomförs en rigorös beräkning av fasen med hjälp av finita elementmetoden, varpå man kan beräkna fas och amplitud från strukturen efterreflektion från en plan våg. Därefter kan man välja ut de geometrierna somkrävs för att styra riktningen av vågpropagationen med en fasgradient.Fysikaliska principerna kan förklaras genom stråloptik eller med hjälp avgeneraliserade Snell's lag. I denna rapport presenteras en design av en planreflektor med elva MIM strukturer där den totala storleken är 5.5 µm. FEMsimulering visade att reflektorn fokuserade ljuset vid våglängden 1.2 µm medden nominella fokallängden 6 µm. Dessa kompakta metamaterial kan eventuellttillverkas på chip för detektering och telekom, vilket löser problemen medatt inkludera konventionella linser i optiska system.

<p dir="ltr">Molecular materials exhibiting bistability between two states are intriguing candidates for next generation electronic devices. Two similar classes of materials, known as spin crossover (SCO) and valence tautomers (VT) respectively, are of particular interest due to their multifunctional properties, which are controllable via several external parameters, such as temperature, light irradiation, pressure, magnetic field, and electric field. In recent years, considerable research has been dedicated to better understanding the underlying principles that govern the behavior of these materials, so that their implementation into nano-based devices might be achieved.</p><p dir="ltr">In this report, a systematic study of the valence tautomer molecule [Co(sq)(cat)(3-tpp)₂] is presented. In the first chapter, the phenomenon of valence tautomerism (VT) occurring in coordination compounds is introduced and described from the perspective of Crystal Field Theory (CFT). Further, the molecular structure and physical properties of the [Co(sq)(cat)(3-tpp)₂] molecule are explored. The properties of the ferroelectric material Polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), and the 2-D Mxene Ti₃C₂ are also discussed.</p><p dir="ltr">The next section details equipment development and experimental methods. Thin films of VT molecules were prepared from solution via a drop-casting approach. For thin film analysis, we have developed a custom made, fully automated Vibrating Sample Magnetometer (VSM) with a sensitivity on the order of 1 × 10^-5 emu, as well as a fully automated, variable temperature, under vacuum electron transport stage, and a magneto-optic Kerr effect apparatus (MOKE). Additional experimental methods used to characterize the VT thin films include X-ray Absorption Spectroscopy (XAS), UV-visible Spectrometry (UV-Vis) and Differential Scanning Calorimetry. Experimental results obtained from these techniques are discussed and analyzed in the third section. PVDF-HFP polarization dependent isothermal spin state switching of [Co(sq)(cat)(3-tpp)₂] is also discussed as well as the effects of doping [Co(sq)(cat)(3-tpp)₂] with Ti₃C₂, followed by a conclusion and an outline of future work.</p>

In this thesis, an investigation into the modal characteristics of novel beam shapes is presented. Sculpting the phase profile of a Gaussian beam can result in the generation of a beam with unique properties. Described in this thesis are Laguerre-Gaussian (LG), Hermite-Gaussian (HG) and Bessel beams (BBs). The diffraction of LG beam modes from a triangular aperture is explored and this effect can be used for the efficient measurement of the azimuthal mode index l that indicates the number of multiples of 2π of phase changes that the field displays around one circumference of the optical axis. In this study, only LG beams with zero radial mode index p, with p + 1 denoting the number of bright high intensity concentric rings around the optical axis, were considered. Then, a powerful approach to simultaneously determine both mode indices of a pure LG beam using the principal component analysis (PCA) algorithm on the observed far-field diffraction patterns was demonstrated. Owing to PCA algorithm, the shape of the diffracting element used to measure the mode indices is in fact of little importance and the crucial step is ‘training' any diffracting optical system and transforming the observed far-field diffraction patterns into the uncorrelated variables (principal components). Our PCA method is generic and it was extended to other families of light fields such as HG, Bessel and superposed beams. This reinforces the widespread applicability of this method for various applications. Finally, both theoretically and experimentally investigations using interferometry show the definitive linkage between both the radial and azimuthal mode indices of a partially coherent LG beam and the dislocation rings in the far-field cross-correlation function (CCF).

<p> This dissertation describes the recent advancements in micromechanical testing that inform how deformation mechanisms in austenitic stainless steels (SS) are affected by the presence of irradiation-induced defects. Austenitic SS is one of the most widely utilized structural alloys in nuclear energy systems, but the role of irradiation on its underlying mechanisms of mechanical deformation remains poorly understood. Now, recent advancement of microscale mechanical testing in a scanning electron microscope (SEM), coupled with site-specific transmission electron microscopy (TEM), enables us to precisely determine deformation mechanisms as a function of plastic strain and grain orientation.</p> <p> </p> <p>We focus on AISI 304L SSs irradiated in EBR-II to ~1-28 displacements per atom (dpa) at ~415 °C and contains ~0.2-8 atomic parts per million (appm) He amounting to ~0.2-2.8% swelling. A portion of the specimen is laser welded in a hot cell; the laser weld heat affected zone (HAZ) is studied and considered to have undergone post-irradiation annealing (PIA). An archival, virgin specimen is also studied as a control. We conduct nanoindentation, then prepare TEM lamellae from the indent plastic zone. In the 3 appm He condition, TEM investigation reveals nucleation of deformation-induced <i>α</i>’ martensite in the irradiated specimen, and metastable <i>ε</i> martensite in the PIA specimen. Meanwhile, the unirradiated control specimen exhibits evidence only of dislocation slip and twinning; this is unsurprising given that alternative deformation mechanisms such as twinning and martensitic transformation are typically observed only near cryogenic temperatures in austenitic SS. Surface area of irradiation-produced cavities contribute enough free energy to accommodate the martensitic transformation. The lower population of cavities in the PIA material enables metastable <i>ε</i> martensite formation, while the higher cavity number density in the irradiated material causes direct <i>α</i>’ martensite formation. In the 0.2 appm He condition, SEM-based micropillar compression tests confirm nanoindentation results. A deformation transition map with corresponding criteria has been proposed for tailoring the plasticity of irradiated steels. Irradiation damage could enable fundamental, mechanistic studies of deformation mechanisms that are typically only accessible at extremely low temperatures. </p>

Despite the central importance of porous electrodes to any advanced electrochemical system, there is no clear answer to “<i>How to make the best electrode</i>?”. The source of ambiguity lies in the incomplete understanding of convoluted material interactions at smaller – difficult to observe length and timescales. Such mesoscopic interactions, however, abide by the fundamental physical principles such as mass conservation. The porous electrodes are investigated in such a physics-based setting to comprehend the interplay among structural arrangement and off-equilibrium processes. As a result, a synergistic approach exploiting the complementary characteristics of controlled experiments and theoretical analysis emerges to allow mechanistic insights into the associated mesoscopic phenomena. The potential of this philosophy is presented by investigating three distinct electrochemical systems with their unique peculiarities.

The absence of long-range order in glassy chalcogenides provides the convenience of changing the elemental ratios and hence the properties over a wide range. The interesting properties exhibited by chalcogenide glasses make them suitable materials for Phase Change Memories (PCM) and other applications such as infrared optical devices, photo-receptors, sensors, waveguides, etc. One of the most remarkable properties of chalcogenides is their electrical switching behavior. Reversible (threshold type) or irreversible (memory type) switching from a high resistance OFF state to a low resistance ON state in glassy chalcogenides occurs at a critical voltage called the threshold/switching voltage (VT). Investigations on the switching behavior and its composition dependence throw light on the local structural effects of amorphous chalcogenide semiconductors and also help us in identifying suitable samples for PCM applications. Thermal analysis by Differential Scanning Calorimetry (DSC) has been extensively used in glass science, particularly for measurements of thermal parameters such as enthalpy of relaxation, specific heat change, etc., near glass transition. Quite recently, the conventional DSC has been sophisticated by employing a composite temperature profile for heating, resulting in the Temperature Modulated DSC (TMDSC) or Alternating DSC (ADSC). Measurements made using ADSC reveal thermal details with enhanced accuracy and resolution, and this has lead to a better understanding of the nature of glass transition. The thermal parameters obtained using DSC/ADSC are also vital for understanding the electrical switching behavior of glassy chalcogenides. The motivation of this thesis was twofold: The first was to develop a novel, high voltage programmable power supply for electrical switching analysis of samples exhibiting high VT, and second to investigate the thermal and electrical switching behavior of certain Se-Te based glasses with Ge and Sb additives. The thesis contains seven chapters: Chapter 1: This chapter provides an overview of amorphous semiconductors (a-SC) with an emphasis on preparation and properties of glassy chalcogenides. The various structural models and topological thresholds of a-SC are discussed with relations to the glass forming ability of materials. The electronic band models and defect states are also dealt with. The essentials of electrical switching behavior of chalcogenides are discussed suggesting the electronic nature of switching and the role of thermal properties on switching. Chapter 2: The second chapter essentially deals with theory and practice of the experimental techniques adopted in the thesis work. The details of the melt-quenching method of synthesizing glassy samples are provided. Considering the importance, the theory of thermal analysis by DSC & ADSC, are discussed in detail, highlighting the advantages of the latter method adopted in the thesis work. The instrumentation and electronics, developed and used for electrical switching analysis are also introduced at a block diagram level. Finally, the methods used for structural analysis are briefed. Chapter 3: This chapter is dedicated to the design and development details of the programmable High Voltage dc Power Supply (HVPS: 1750 V, 45 mA) undertaken in the thesis work. The guidelines used for power supply topology selection, the specifications and block diagram of the HVPS are provided in that sequence. The operation of the HVPS is discussed using the circuit diagram approach. The details of software control are also given. The performance validations of the HVPS, undertaken through voltage & current regulation tests, step & frequency response tests are discussed. Finally, the sample-test results on the electrical switching behavior of representative Al20As16Te64 and Ge25Te65Se10 samples, obtained using both the current & voltage sweep options of the HVPS developed are illustrated. Chapter 4: Results of the thermally induced transitions governed by structural changes which are driven by network connectivity in the GexSe35-xTe65 (17 ≤ x ≤ 25) glasses, as revealed by ADSC experiments, are discussed in this chapter. It is found that the GexSe35-xTe65 glasses with x ≤ 20 exhibit two crystallization exotherms (Tc1 & Tc2), whereas those with x ≥ 20.5, show a single crystallization reaction upon heating (Tc). The glass transition temperature of GexSe35-xTe65 glasses is found to show a linear, but not-steep increase, indicating a progressive and not an appreciable build-up in network connectivity with Ge addition. The exothermic reaction at Tc1 has been found to correspond to the partial crystallization of the glass into hexagonal Te and the reaction at Tc2 is associated with the additional crystallization of rhombohedral Ge-Te phase. It is also found that the first crystallization temperature Tc1 of GexSe35-xTe65 glasses of lower Ge concentrations (with x ≤ 20), increases progressively with Ge content and eventually merges with Tc2 at x = 20.5 (<r> = 2.41); this behavior has been understood on the basis of the reduction in Te-Te bonds of lower energy and an increase in Ge-Te bonds of higher energy, with increasing Ge content. Chapter 5: This chapter deals with the electrical switching studies on GexSe35-xTe65 (17 ≤ x ≤ 25) glasses, with an emphasis on the role of network connectivity/rigidity on the switching behavior. It is found that the switching voltage (VT) increases with Ge content, exhibiting a sudden jump at x=20, the Rigidity Percolation Threshold (RPT) of the system. In addition, the switching behavior changes from memory to threshold type at the RPT and the threshold switching is found to be repetitive for more than 1500 cycles. Chapter 6: In this chapter, the results of thermal analysis (by ADSC) and electrical switching investigations on SbxSe55-xTe45 (2 ≤ x ≤ 9) are discussed. It is found that the addition of trivalent Sb contributes very meagerly to network growth but directly affects the structural relaxation effects at Tg. Further, SbxSe55-xTe45 glasses exhibit memory type electrical switching, which is understood on the basis of poor thermal stability of the samples. The metallicity factor is observed to outweigh the network factor in the composition dependence of VT of SbxSe55-xTe45 glasses. Chapter 7: The chapter 7 summarizes the results obtained in the thesis work and provides the scope for future work. The references are cited in the text along with the first author’s name and year of publication, and are listed at the end of each chapter in alphabetical order.