Rozprawy doktorskie na temat „Phonon Liquid Electron Crystal”

This thesis addresses a theoretical study of the problem of a single impurity embedded in a one-dimensional system of interacting electrons in presence of electron-phonon coupling. First we consider a system with a featureless point-like potential impurity, followed by the case of a resonant level hybridised with a Luttinger Liquid. The stress is made on a more fundamental problem of a featureless scatterer, for which two opposite limits in the impurity strength are considered: a weak scatterer and a weak link. We have found that, regardless of the transmission properties of phonons through the impurity, the scaling dimensions of the conductance in these limits obey the duality condition, \( \triangle_{WS}\) \( \triangle_{WL}\) = 1, known for the Luttinger Liquid in the absence of phonons. However, in the case when the strength of phonon scattering is correlated with electron scattering by the impurity, we find a nontrivial phase diagram with up to three fixed points and a possibility of a metal-insulator transition. We also consider the case of a weakly interacting electron-phonon system in the presence of a single impurity of an arbitrary scattering potential. In the problem of a resonant level attached to the Luttinger Liquid we show that the electron-phonon coupling significantly modifies the effective energy-dependent width of the resonant level in two different geometries, corresponding to the resonant and anti-resonant transmission in the Fermi gas.

We studied the structural instabilities of one-dimensional (1D) and quasi-one-dimensional (Q1D) electron-phonon systems at low temperature through two models, SuSchrieffer-Heeger (SSH) and molecular crystal (CM) with and without spin. The phase diagrams are obtained using a Kadanoff-Wilson renormalization group approach (GR). For the 1D half-filled system the study of the frequency dependence of the electronic gap allowed us to connect continuously the two limits, adiabatic and non-adiabatic. The Peierls and Cooper channels interference and the quantum fluctuations reduce the gap. A regime change occurs when the frequency becomes of the order of mean field gap, marking a quantum-classical crossover that is the Kosterlitz-Thouless type. At this level, the effective coupling behaves in power law function on frequency. For the case with spin, a gapped Peierls state is maintained in the non-adiabatic limit, while for the case without spin, the system transits to ungapped disordered state, namely the Luttinger liquid stat (LL). For the SSH model without spin, the GR confirms the existence of a threshold phonon coupling beyond which the gap is restored. The study of the rigidities of the two models without spin allowed us to trace the main features of the LL state predicted by the bosonization method. The study of the Holstein-Hubbard model has allowed us not only to reproduce the phase diagrams already obtained by the Monte Carlo method, but to highlight two additional phases, namely, free fermions phase and the bond charge-density-wave phase. We have extended this study to the quarter-filled Q1D Peierls systems at finite temperature. Within the SSH model, an unconventional superconducting phase with spin singlet symmetry SS-s emerges at low temperature when the deviation to the perfect nesting of the Fermi surface is strong enough. Peierls-SS transition is characterized by the presence of a quantum critical point at low frequency and by a power law behavior of the transition temperature as a function of frequency with an exponent identical to one of 1D system. This exponent which universality has been verified contrasts with the BCS result. Coulomb interactions have been introduced through the study of the extended SSH-Hubbard model. The extension of this work to half-filled SSH and CM cases was also performed.

The contents of this dissertation relate to a liquid crystal light valve which is addressed by an electron beam. The light valve has been configured with a computer aided designed optical projection system, to produce an electron beam addressed liquid crystal light valve projector. The projector is capable of turning an electrical signal into a corresponding projected picture. A minimum resolution of 33um was demonstrated in a smectic-A liquid crystal light valve and one of 40um in a dyed phase change guest-host liquid crystal light valve. The diameter of the active area of the light valve was 45mm. Crucial to the realization of the projector was the patented invention and design of an electrically highly anisotropic disc of 47mm diameter which was approximately 2mm thick. The disc, which was conducting through its thickness and insulating across its plane, formed the top interface of the liquid crystal light valve and permitted the electron beam to deposit a charge pattern which could be conveyed to the thin liquid crystal layer without loss of resolution. The disc was made using a specially constructed piece of apparatus wherein the holes in a glass capillary array were filled with a low melting point alloy. Discs were made using three different low melting point alloys and their various merits were considered. Consideration was also given to developing the deflection coils used in this projector. Computer aided design resulted in a deflection coil system capable of a resolution of over 8 x 10⁸ pixels in a 50mm x 50mm frame at a half angular aperture of 1mrad. In order to evaluate the resolution of the light valve, a micro-computer controlled dot pattern generator was built. This was used to drive the deflection coils in such a way as to control both the dwell time and position of the electron beam spot. Lines of different spacings were written on the light valve. Electron and optical micrographs are presented to demonstrate the quality of the anisotropic disc. Photographs and optical micrographs are included to show the pictures which were obtained from the projector and also the lines written on the light valve.

The polaron problem is studied, on an infinite lattice, using the continuous-time path-integral quantum Monte Carlo scheme The method is based on the Feynman technique to analytically integrate out the phonon degrees of freedom. The transformed problem is that of a single electron with retarded self-interaction in imaginary time. The Metropolis algorithm is used to sample an ensemble of electron trajectories with twisted (rather than periodic) boundary conditions in imaginary time, which allows dynamic properties of the system to by measured directly. The method is numerically "exact", in the sense that there are no systematic errors due to finite system size, trotter decomposition or finite temperature The implementation of the algorithm in continuous imaginary time dramatically increases computational efficiency compared with the traditional discrete imaginary time algorithms.

By using cryo-electron microscopy, we analyzed the morphology and structure of long double-stranded DNA chains condensed upon addition of varying amounts of the tetravalent polycation spermine (polyamine). Experiments have been performed i) with chains diluted in the bulk and ii) with individual chains confined in a virus capsid.Bulk experiments have been done with lambda DNA (48.5 kbp) at low concentration (0.03 mM Ph) and in low salt conditions (10 mM Tris HCl, 1 mM EDTA, pH 7.6). We explored a wide range of spermine concentration, from the onset of precipitation (0.05 mM sp) up to above the resolubilization limit (400 mM sp). Sixteen min after mixing spermine and DNA, samples have been trapped in thin films and vitrified in liquid ethane to keep ionic conditions unchanged, and imaged at low temperature with low doses of electrons (cryoTEM). DNA chains mostly form large aggregates of toroids in which DNA chains are hexagonally packed with interhelical spacings of 2.93, 2.88, and 2.95 nm at 0.05, 1 and 100 mM spermine, respectively, in agreement with previous X-ray data. At higher spermine concentration (200 mM), hexagonal toroids are replaced by cholesteric bundles with a larger interhelical spacing (3.32 nm). We conclude that the shape and the structure of the liquid crystalline sp-DNA condensates are linked to the DNA interhelix spacing and determined by the ionic conditions i.e. by the cohesive energy between DNA strands. Outside of the precipitation domain (400 mM spermine), DNA chains form a soluble network of thin fibers (4-6 nm in diameter) that let us reconsider the state of these DNA chains in excess of spermine. We also designed experiments to visualize condensates formed 6-60 sec after mixing Lambda DNA with 0.05 mM spermine, under identical buffer conditions. Among multiple original shapes (not found after 16 min), the presence of stretched and helical elongated fibers seen only 9sec after addition of spermine let us propose that DNA chains are immediately stretched upon addition of spermine, relax into helical structures and finally form small toroids (containing in some cases less than one Lambda chain) that further grow and aggregate. We also analyzed the dimensions and structural details of the complete collection of toroids, and reveal the existence of geometric constraints that remain to be clarified. Since it was only exceptionally possible to prevent the aggregation of DNA in dilute solution, we used another approach to observe the collapse of single DNA chains. We handled a population of T5 viruses containing a fraction of their initial genome (12-54 kbp long). The Na-DNA chain, initially confined in the small volume of the capsid (80nm in diameter) is collapsed by the addition of spermine. Compared to the first set of experiments, we explored a higher DNA concentration range (0.45 mM Phosphates in the whole sample) and the spermine concentration was varied from 0.05 to 0.5 mM (which corresponds to much lower +/- charge ratios). Experiments are thus performed close to the precipitation line, in the coexistence region, between the region where all chains are in a coil conformation, and the region where all chains are collapsed into toroids. We describe the existence of intermediate states between the coil and the toroidal globule that were not reported yet. In these "hairy toroids", part of the DNA chain is condensed in the toroid and the other part stays uncondensed outside of it. The interhelical spacing was also measured; it is larger in these partly-condensed toroids than in the fully organized toroids formed at higher spermine concentration.These two series of experiments show the interest of cryoEM to analyze the structural polymorphism and local structure of spermine-DNA aggregates. We also demonstrated how the confinement interferes with DNA condensation and the interest to investigate such effects that are important in the biological context.

Ce travail de thèse a été dédié à l’élaboration et l’étude de nouveaux matériaux hybrides obtenus par la fonctionnalisation de molécule-aimants (en anglais single-molecule magnets, SMMs) et de complexes à transfert d’électron. Le premier chapitre fait un état de l’art des deux classes de composés magnétiques utilisées dans ce travail : les molécule-aimants et les systèmes à transfert d’électrons. Une brève description des systèmes magnétiques hybrides présents dans la littérature est ensuite présentée dans le but d’illustrer les motivations qui ont conduit à ce travail. Le chapitre II décrit la fonctionnalisation des molécule-aimants de type [Mn12] dans le but d’obtenir des systèmes cristaux liquides hybrides. Deux approches ont été étudiées : (a) la fonctionnalisation des ligands périphériques avec des groupements fortement lipophiles (longues chaines alkyle) ou (b) le greffage de promoteurs mésogènes par l’intermédiaire d’espaceurs aliphatiques flexibles. Les chapitres III à V présentent les études sur des carrés moléculaires à ponts cyanure {Fe2Co2} qui montrent un transfert d’électron thermo- et photo-induit. Le chapitre III discute de la possibilité de moduler le processus de transfert d’électron de ces carrés moléculaires via le changement du contre anion. La fonctionnalisation du carré moléculaire {Fe2Co2} avec de chaines aliphatiques et son impact induit sur les propriétés physiques à l’état solide et en solutions sont décrits dans le chapitre IV. Le chapitre V discute de l’effet de la fonctionnalisation avec des groupements fortement électrodonneurs, tels que les groupements méthoxy, sur le processus de transfert d’électron des carrés moléculaires {Fe2Co2}
The work presented in this thesis was focused on the design and investigation of novel hybrid materials via ligand functionalization of the single-molecule magnets (SMMs) and electron transfer complexes. Chapter I contains general information about these two classes of the magnetic systems. In order to illustrate the motivation behind our work, a brief review on previously reported soft hybrid magnetic systems, is presented. Chapter II is dedicated to the functionalization of [Mn12]-based SMMs towards hybrid liquid crystalline systems via two different approaches: (a) the functionalization of peripheral ligands with strongly lipophilic groups (long alkyl chains), or (b) the grafting of mesogenic promoters through flexible aliphatic spacers. Chapters III – V are focused on cyanido-bridged molecular {Fe2Co2} squares that exhibit thermally or photo-induced electron transfer. Thus, in Chapter III, the possibility to modulate the electron transfer properties in {Fe2Co2} molecular squares via the use of different counter-anion is discussed. The functionalization with long aliphatic chains and its influence over the properties of {Fe2Co2} molecular squares in solid state and solutions are discussed in Chapter IV. Finally, the effect of the ligand functionalization with strongly electron density donating groups (methoxy) over the electron transfer properties of {Fe2Co2} molecular squares is investigated in Chapter V

The vectorial nature (polarization) of light plays a significant role in light-matter interaction that leads to a variety of optical devices. The polarization property of light has been exploited in imaging, metrology, data storage, optical communication and also extended to biological studies. Most of the past studies fully explored and dealt with the conventional polarization state of light that has spatially symmetric electrical field geometry such as linear and circular polarization. Recently, researchers have been attracted to light whose electric field vector varies in space, the so-called optical vector vortex beam (VVB). Such light is expected to further enhance and improve the efficiency of optical systems. For instance, a radially polarized light under focusing condition is capable of a tighter focus more than the general optical beams with a uniform polarization structure, which improves the resolution of the imaging system [1]. Interaction of ultrafast laser pulses with matter leads to numerous applications in material processing and biology for imaging and generation of microfluidic systems. A femtosecond pulse, with very high intensities of (10^{12} - 10^{13} W/cm^2), has the potential to trigger a phenomenon of optical breakdown at the surface and therefore induce permanent material modification. With such high intensities and taking into account the fact that most materials possess large bandgap, the interaction is completely nonlinear in nature, and the target material can be modified locally upon the surface and even further in bulk. The phenomenon of optical breakdown can be further investigated by studying the nonlinear absorption. Properties like very short pulse duration and the high irradiance of ultrashort laser pulse lead to more precise results during the laser ablation process over the long pulsed laser. The duration of femtosecond laser pulse provides a high resolution for material processing because of the significant low heat-affected zone (HAZ) beyond the desired interaction spot generated upon irradiating the material. Under certain condition, the interaction of intense ultrashort light pulses with the material gives rise to the generation of periodic surface structures with a sub-micron periodicity, i.e., much smaller than the laser wavelength. The self-oriented periodic surface structures generated by irradiating the material with multiple femtosecond laser pulses results in improving the functionality of the material's surface such as controlling wettability, improving thin film adhesion, and minimizing friction losses in automobile engines, consequently, influences positively on many implementations. In this work, we introduced a new method to study complex polarization states of light by imprinting them on a solid surface in the form of periodic nano-structures. Micro/Nanostructuring of diamond by ultrafast pulses is of extreme importance because of its potential applications in photonics and other related fields. We investigated periodic surface structures usually known as laser-induced periodic surface structures (LIPSS) formed by Gaussian beam as well as with structured light carrying orbital angular momentum (OAM), generated by a birefringent optical device called a q-plate (QP). We generated conventional nano-structures on diamond surface using linearly and circularly polarized Gaussian lights at different number of pulses and variable pulse energies. In addition, imprinting the complex polarization state of different orders of optical vector vortex beams on a solid surface was fulfilled in the form of periodic structures oriented parallel to the local electric field of optical light. We also produced a variety of unconventional surface structures by superimposing a Gaussian beam with a vector vortex beam or by superposition of different order vector vortex beams. This thesis is divided into five chapters, giving a brief description about laser-matter interaction, underlying the unique characterization of femtosecond laser over the longer pulse laser and mechanisms of material ablation under the irradiation of fs laser pulse. This chapter also presents some earlier studies reported in formation of (LIPSS) fabricated on diamond with Gaussian. The second chapter explains the properties of twisted light possessing orbital angular momentum in its wavefront, a few techniques used for OAM generation including a full explanation of the q-plate from the fabrication to the function of the q-plate, and the tool utilized to represent the polarization state of light (SoP), a Poincar'e sphere. Finally, the experimental details and results are discussed in the third and fourth chapters, respectively, following with a conclusion chapter that briefly summarizes the thesis and some potential application of our findings.

Dans cette thèse, nous avons développé la synthèse de nouveaux matériaux magnétiques hybrides afin d’améliorer la mise en forme de ces systèmes. Une partie de notre travail a consisté à fonctionnaliser la partie organique de matériaux moléculaires possédant des propriétés magnétiques remarquables, par des groupes fonctionnels connus pour induire des phases cristal-liquide ou pour augmenter la solubilité. Nous avons réalisé la fonctionnalisation rationnelle (i) de molécules aimants (Single-Molecule Magnets, SMM), (ii) de systèmes à conversion de spin et (iii) à transfert d'électrons, induisant ainsi des matériaux plus solubles et des phases cristal liquide.Le Chapitre I présente trois classes importantes de complexes magnétiques: les molécules-aimants, les systèmes à conversion de spin et de transfert d'électrons. Afin d’illustrer les motivations de notre travail une étude bibliographique dédiée aux matériaux hybrides magnétiques est ensuit présentée. La fonctionnalisation rationnelle des SMM et des systèmes à conversion de spin, respectivement, vers des phases cristallines liquides ont été discutés dans le Chapitre II et III. De nouveaux complexes fonctionnalisés à base de Mn12, FeII/triazole et [FeII(LN2O2)(LN)2] ont été obtenus. La conservation des propriétés magnétiques après fonctionnalisation du ligand a été confirmée, mais malheureusement, ces nouveaux composés ne montrent pas de comportement mésomorphe en dessous de la température de décomposition. Le Chapitre IV porte sur la fonctionnalisation des complexes à transfert d'électrons. La fonctionnalisation du ligand alkyle confère une bonne solubilité à ces complexes, et le comportement commutable activé thermiquement à l’état solide a ainsi pu être transféré à des solutions diluées
In this thesis, we tried to develop hybrid magnetic material chemistry in order to get soft systems that can be easy-processable. This work deals with functionalization of the organic part of interesting molecule-based magnetic materials by groups known to induce liquid crystal phase or to increase the solubility. We achieved the rational functionalization of molecule-based magnetic materials, like (i) Single-Molecule Magnets (SMM), (ii) Spin Crossover (SC), and (iii) Electron Transfer (ET) systems, towards more soluble systems and liquid crystal phases.Chapter I contains general information about three important classes of magnetic complexes: SMMs, SC and ET systems. In order to illustrate the motivation of our work, a bibliographic study about hybrid magnetic materials is then presented. Rational ligand functionalization of SMMs and SC systems towards liquid crystalline phases are discussed in Chapter II and III, respectively. New functionalized Mn12 complexes, FeII/triazole-based and [FeII(LN2O2)(LN)2] systems were obtained. The conservation of magnetic properties after ligand functionalization was confirmed, but unfortunately, these new compounds do not show mesomorphic behaviour below the decomposition temperature. The Chapter IV is focused on ligand functionalization of ET complexes. Alkyl functionalization of the ligand provides a good solubility to these complexes, and the thermally-induced switchable behaviour observed in solid state has been successfully transferred to dilute solutions

Développer des méthodes efficaces pour mettre en forme les matériaux moléculaires magnétiques demeure un enjeu majeur et représente une étape essentielle en vue de possible applications. A cet égard, l’élaboration d’hybrides magnétiques présentant des propriétés de cristaux-liquides ou des systèmes solubles apparait comme une approche prometteuse. Ce travail de thèse a été axé sur la conception, la synthèse et la caractérisation de nouveaux hybrides basé sur des molécule-aimants (SMMs), des complexes à conversion de spin (SCO) et systèmes à transfert d'électrons (ET). Le chapitre I contient des informations générales et concepts théoriques sur ces trois classes de complexes magnétiques (SMM, SCO et ET) ainsi qu’un aperçu bibliographique sur les hybrides magnétiques connus. Le chapitre II est axé sur nos travaux de fonctionnalisation de molécules-aimants basés sur le complexe Mn12, en vue d’obtenir des phases cristaux-liquides. Dans le chapitre III, l’étude d’une série de complexes à conversion de spin de type Fe(II)-pyridylbenzohydrazone au sein de phases cristallines ou de phases molles est décrite. Le chapitre IV est dédié à l’étude de complexes tetra nucléaire a pont cyanure de type {Fe2M2} (M = Co2+, Ni2+),qui sont connus pour présenter des propriétés de transfert de charge ou SMM avec l’ion Co(II) etNi(II), respectivement. Dans ces trois chapitres expérimentaux, l’influence de la fonctionnalisation des ligands sur l’auto-organisation et les propriétés thermiques et magnétiques des matériaux résultants est discutée en détail
Developing efficient methods to process molecular magnetic materials remains a considerable challenge and constitutes one of the critical steps toward possible applications. In this scope, the development magnetic hybrids featuring liquid crystal properties or improved solubility appears as a promising approach. This thesis work aimed to design, synthetize and characterize new hybridmaterials based on the single-molecule magnets (SMMs), spin crossover (SCO) and electrontransfer (ET) complexes. Chapter I contains general information and theoretical concepts on these three classes of magnetic complexes (SMMs, SCO and ET complexes), followed by a bibliographicsurvey on hybrid magnetic materials. Chapter II, rational is focused on the functionalization ofMn12-based SMM towards liquid crystalline phases. In Chapter III, a series of pyridylbenzohydrazone-based Fe(II) SCO complexes is investigated in both crystalline and soft matter phase. Chapter IV is dedicated to the study of cyanido-bridged {Fe2M2} molecular squares(M = Co(II), Ni(II)), which are known to exhibit SMM and thermally- or photo induced ET,respectively with Co(II) and Ni(II). In these three experimental chapters, the influence of ligand functionalization on self-organization, thermal and magnetic properties of the resulting materials is discussed in detail

La structure moléculaire d'un cristal liquide cholestérique (CLC) est hélicoïdale et donne lieu à des propriétés optiques remarquables comme la réflexion sélective de la lumière. La structure cholestérique soulève des questions fondamentales comme la relation entre chiralités moléculaire et mésoscopique, et son impact sur les propriétés optiques. Elle est omniprésente en biologie (organisation de la chitine, de la cellulose, du collagène ou de la chromatine). Elle est aussi utilisée en technologie : en cosmétologie, dans les afficheurs nématiques super-torsadés, les écrans réflecteurs, les capteurs de température ou pression, les matériaux pour les applications photoniques en général. Le but du présent travail est de décrire et comprendre l'interaction de la lumière avec différents types de structures hélicoïdales non-monotones élaborées dans cette thèse - films cholestériques synthétiques (monocomposant ou hybrides i.e. dopés en nanoparticules d'or) - ou dans un matériau biologique (carapace du scarabée Chrysina gloriosa). Différentes techniques de caractérisation optique ont été utilisées suivant le matériau à étudier et les questions posées. La partie principale du manuscrit est dédiée aux microlentilles et micro-miroirs cholestériques. Nous avons étudié la texture polygonale cholestérique et mis en évidence qu'elle se comporte comme un réseau de microlentilles chirales à l'aide de la microscopie confocale couplée à la spectrophotométrie. Ces microlentilles organiques, élaborées en deux étapes par auto-assemblage, ont la particularité d'être sélectives en longueur d'onde. Nous avons ensuite montré que la texture polygonale de la carapace de Chrysina gloriosa, analogue biologique, est un réseau de micro-miroirs sphériques et de microlentilles convergentes. La seconde partie du manuscrit est consacrée à l'élaboration de matériaux hybrides CLC et nanoparticules d'or et à l'étude de leurs propriétés optiques. Les propriétés optiques de ces nanocomposites ont été sondées à l'aide de différentes techniques (résonance plasmon, spectrométrie Raman etc)
The molecular structure of a cholesteric liquid crystal (CLC) is helical and gives rise to outstanding optical properties like the selective reflection of the light. Cholesteric structure raises fundamental questions such as the relationship between molecular chirality and mesoscopic chirality, and its impact on optical properties. It is omnipresent in biology (organisation of chitin, cellulose, collagen or chromatin). It is also used in technology: cosmetology, super-twisted nematic displays, reflective screens, temperature or pressure sensors, materials for photonic applications in general. The purpose of this work is to describe and understand the interaction of light with different types of non-monotonous helical structures elaborated in this thesis - synthetic cholesteric films (single-component or hybrid i.e. doped with gold nanoparticles) - or in a biological material (Chrysina gloriosa beetle). Several optical characterisation techniques have been used, depending on the sample to study and the questions which are rised. The main part of the manuscript is dedicated to cholesteric microlenses and micro-mirrors. We studied the cholesteric polygonal texture and highlighted that it acts as a chiral microlens array by using confocal microscopy coupled to spectrophotometry. These organic microlenses, developed in a two-step process by self-assembly, have the specificity of being wavelength-selective. We then showed that the polygonal texture of Chrysina gloriosa, as a biological analogous, is an array of spherical micro-mirrors and convergent microlenses. The second part of the manuscript is devoted to the elaboration of hybrid materials composed of CLC and gold nanoparticules and the study of their optical properties. Optical properties of these nanocomposites were probed using various techniques (plasmon resonance, Raman spectroscopy etc)

In this thesis, geometry is used as a basis for conducting experiments aimed at growing and arranging inorganic minerals on curved interfaces. Mineralisation is directed using crystalline and liquid-crystalline metallic soaps and surfactant/water systems as templates.¶ A review of the history, syntheses, structure and liquid crystallinity of metallic soaps and other amphiphiles is presented as a foundation to understanding the interfacial architectures in mesostructured template systems in general.¶ In this study, a range of metallic soaps of varying chain length and cation type are synthesised and characterised to find potentially useful templates for mineral growth. These include alkaline-earth, transition metal, heavy metal and lanthanide soaps. These are systematically characterised using a variety of analytical techniques, including chemical analyses, x-ray diffraction (XRD) infrared spectroscopy (IR) and differential scanning calorimetry (DSC). Their molecular and crystal structures are studied using transmission electron microscopy (TEM), cryo-TEM, electron diffraction (ED), electron paramagnetic spin resonance (EPR), absorption spectroscopy (UV-VIS), high resolution laser spectroscopy, atomic force microscopy (AFM), nuclear magnetic resonance spectroscopy, scanning electron microscopy (SEM), electron dispersive x-ray analysis (EDXA), thermal gravimetric analysis (TGA) and magnetic measurements. Models for the molecular and crystal structures of metallic soaps are proposed. The soaps are predominantly lamellar crystalline or liquid crystalline lamellar rotor phases with tilted and/or untilted molecular constituents. These display evidence of varying degrees of headgroup organisation, including superstructuring and polymerisation. A single crystal structure is presented for a complex of pyridine with cobalt soap. Simple models for their structure are discussed in terms of their swelling properties in water and oils. Experiments are also presented to demonstrate the sorbent properties of aluminium soaps on oil spills.¶ The thermotropic liquid crystallinity of alkaline earth, transition metal, heavy metal and lanthanide soaps is investigated in detail. This is done to assess their suitability as templates, and to document their novel thermotropic behaviour, particularly the relatively unknown lanthanide soaps. Liquid crystalline behaviours are studied using high-temperature XRD (HTXRD), hot-stage optical microscopy and DSC. Models for a liquid crystalline phase progression from crystals to anisotropic liquids are discussed in terms of theories of self-assembly and interfacial curvature. The terminology required for this is drawn from various nomenclature systems for amphiphilic crystals and liquid crystals. General agreement with previous studies is reported for known soaps, while liquid crystallinity is demonstrated in the lanthanide and some non-lanthanide soaps for the first time. A general phase progression of crystalline lamellar through liquid crystalline lamellar to non-lamellar liquid crystalline is discussed in terms of models concerned with the molecular and crystal structures of the soaps and their phase transitions via headgroup and chain re-arrangements.¶ Experiments aimed at guiding growth of metal sulfides using metallic soaps as templates are described, and a model for this growth is discussed. Metal sulfides have been successfully grown by reacting crystalline and liquid crystalline transition metal and heavy metal soaps with H2S gas at room temperature and at elevated temperature. These have been characterised using XRD, TEM, ED and IR. Sulfide growth is demonstrated to be restricted and guided by the reacting soap template architecture. Zinc, cadmium, indium and lead soaps formed confined nanoparticles within the matrix of their reacting soap template. In contrast, curved and flat sheet-like structures, some resembling sponges were found in the products of sulfided iron, cobalt, nickel, copper, tin and bismuth soaps. A model to explain this behaviour is developed in terms of the crystal and liquid crystal structures of the soaps and the crystal structures of the metal sulfide particles.¶ Liquid crystalline iron soaps have been subjected to controlled thermal degradation yielding magnetic iron oxide nanoparticles. Some XRD and TEM evidence has been found for formation of magnetic mesostructures in heat-treated iron soaps. Models for the molecular and liquid crystalline structure of iron soaps, their thermotropic phase progression and eventual conversion to these magnetic products are discussed. Systematic syntheses of mesoporous silicates from sheeted clays are discussed.¶The templates that have been used are cationic surfactants and small, organic molecular salts. Experiments are reported where a cooperative self-assembly of surfactant/water/kanemite plus or minus salt and oils yields 'folded sheet materials' (FSM'S). Templating of kanemite has also been achieved using cobalt cage surfactants. A theoretical prediction of the specific surface areas and specific volumes of homologous sets of FSM's gave excellent agreement with measured values. The geometry and topology of the mesostructures are discussed. A theoretical model is also discussed regarding the curvature found in the sheets of natural clays , and results of templating clays and silica using metallic soaps are presented. Experiments and a model for low temperature nucleation and growth of microporous silicalite-1 are described in terms of silica templating by water clathrates.¶ Finally, the problem of finding minimal surface descriptions of crystal networks is addressed. Combinatoric methods are used to disprove the existence of possible embeddings of type I and II clathrate networks in non-self intersecting periodic minimal surfaces. The crystal network of the clathrate silicate, melanophlogite is successfully embedded in the WI-10 self-intersecting surface. Details of a previously unreported, genus-25 periodic surface with symmetry Im3m are discussed.

Etude parrpe et par des mesures de la conductivite dc et de la reponse dielectrique ac hyperfrequence. Mise en evidence de la nature radicalaire de type pi du systeme, a l'etat cristallin comme en solution; effet du solvant et de la temperature; observation de sauts de l'electron non apparie d'un macrocycle a l'autre a une frequence voisine de 1 mhz. Mise en evidence de la possibilite de formation de deux systemes cristallins (empilement de chaines ou de plans paralleles) et de leur caractere 1d ou 2d au moyen du modele de richards. La susceptibilite du systeme mesomorphe indique un desordre magnetique comparable a celui de la phase liquide; la conductivite est celle des systemes desordonnes. Les cristaux solvates sont des semiconducteurs moleculaires intrinseques

Thermoelectric materials play an important role in harvesting the waste heat into useful electrical energy. Since thermoelectricity can lead to a clean energy conversion technology, it is important to find suitable TE materials. The state-of-the-art thermoelectric materials comprises mostly of tellurides due to their favourable transport properties. In this thesis, the structural and thermoelectric properties of copper telluride based alloys have been explored. Copper telluride belongs to the “Phonon Liquid Electron Crystal (PLEC) class of materials owing to its mobile Cu ions which migrates easily inside the crystal lattice. The “mobile” Cu ions restrict the propagation of transverse phonon vibrations during heat transfer. This facilitates the reduction of thermal conductivity making it a suitable choice as thermoelectric material. However, formation of copper vacancies results in high hole carrier concentration (~ 1021 cm-3), which degrades the thermoelectric properties and long-term stability of Cu2Te. Moreover, the crystal structure corresponding to the different phases in Cu-Te is still ambiguous. This pose challenges in proper understanding of the properties of the Cu-Te alloys. Therefore, in the first part of the thesis, the formation of different crystal structures with changes in stoichiometry between Cu and Te has been investigated. The increase in carrier concentration with decrease in Cu:Te stoichiometry was observed. High carrier concentration led to poor power factor and lower thermoelectric figure of merit (zT). It was concluded that in order to enhance the thermoelectric performance of Cu2Te, the carrier concentration has to be decreased by compensating the copper vacancies. In the second part of the thesis, Cu2Te was alloyed with Fe to tune the charge carrier concentration. Substitution of trivalent Fe at the monovalent Cu site resulted in the compensation of hole-carrier concentration and led to an enhancement in power factor. The ‘liquid-like’ mobility of Cu ions was also suppressed as confirmed from the higher specific heat capacity values. The figure of merit was improved for the Fe alloyed samples. The final part of the thesis deals with further improving the thermoelectric properties of Cu2Te by alloying with Sb2Te3. The increase in the Sb2Te3 phase content helped in reducing the electrical as well as thermal conductivity of Cu2Te. This in turn enhanced the figure of merit to ~0.6 at 600 K. Till date, Sb2Te3 is known to be an effective thermoelectric material near room temperature. However, the results obtained herein shows that the high temperature zT as well as the mechanical strength of Sb2Te3 can also be improved in such a composite system of Cu2Te-Sb2Te3

博士
國立成功大學
光電科學與工程學系
100
In recent years, axially symmetric optical technology has been widely used in laser and optical systems, and has also been increasingly developed in communication, display, optoelectronics, and bio-photonics fields. However, building complex optical components are challenging in the design of axially symmetric optical systems. With the development of the optical and electrical properties of liquid crystal materials, liquid crystal is gradually used in the production of axially symmetric components. The axially symmetric liquid crystal device fabrication technology has been well developed, breaking through the traditional contact fabricating method using new non-contact production methods such as photo-alignment. This technique involves the doping of azo derivatives (e.g., azobenzene, azo dyes) in liquid crystal materials. The adsorption of azo dyes in a dye-doped liquid crystal (DDLC) film is achieved through a single pump beam. Light-induced dye adsorption is the main mechanism of liquid crystal photo-alignment, which conclusively results from the positive/negative torque effect, photoisomerization effect, and adsorption/desorption. Single-sided and double-side axially symmetric photo-alignment liquid crystal devices were produced via the method described above. This study consists of three experiments based on the fabricating technique of axially symmetric photo-alignment liquid crystal devices. (1) Using the optical properties of a single side axially symmetric photo-alignment liquid crystal device (homogeneous-radial device), we detected the variations of the disclination line in the spiral structure formed by liquid crystal molecules to measure the helical twisting power (HTP) of a chiral dopant in liquid crystal materials. The HTP measured using an axially symmetrical liquid crystal film is more accurate than that using other methods such as the Cano wedge cell and the reflective spectrum of a cholesteric liquid crystal. In addition, this novel method can be used for measuring very low doping concentrations of the chiral dopant in liquid crystal materials. (2) The special polarization converter, which is formed by combining these axially symmetric photo-alignment liquid crystal devices, can be applied to the axially symmetric optical system. The axially symmetric polarization converter can generate a special optical field and polarization for axially symmetric optics. Such axially symmetric liquid crystal devices can be modulated by applying voltage. These devices are useful for simplifying complex axially symmetric optical systems. Moreover, the special design of axially symmetric devices can be utilized for applications of laser systems. (3) The axially symmetric liquid crystal device can convert a Gaussian laser beam into a donut-shaped laser beam. Moreover, it can modulate the shape of a laser beam by applying voltage. Notably, this device can be used for infrared wavelength applied for biophotonics application, and can also be tuned by applying voltage. In addition, this novel liquid crystal device can be utilized in a simple optical system for converting a differently shaped laser beam (e.g., petal-type). The device developed in this study has substantially increased the value of the application and will contribute to the development of an optical tweezer system.

博士
國立成功大學
光電科學與工程學系
101
The hole-patterned LC lens possesses the advantages of simple fabrication and strong tunable-focus capability. However, because of non-uniform symmetrical electrical fields produced from a circular-hole electrode, the LC molecules in the hole-region easily orient along two opposite directions for homogeneous LC cells, leading to the formation of a disclination line. The disclination line will slow down the response time and lower the image quality. Based on our initial study on the large apertures of LC lenses, disclination lines and zigzag lines typically occur in cells. Unfortunately, zigzag lines and disclination lines will possibly link to each other and permanently stay in the cells to degrade the performance of LC lenses. Therefore, we experimentally study and conclude that suitable rubbing conditions in cells will effectively prevent the problem of linked lines. For convenient operation of the hole-patterned LC lens, we use the method of polymer stabilization to successfully prevent disclination lines in LC lenses. After successfully using the polymer stabilization method to prevent the occurrence of disclination lines, we further increase the concentration of monomers to fabricate coaxially bifocal (CB) LC lenses, and this method is called photo-polymerization. The characteristics of a tunable CB are clearly exhibited when the voltage applied is continuously increased, eventually disappearing until only one focus is left when significantly higher voltages are applied. We simultaneously demonstrate two types of tunable CB LC lenses fabricated via different photocurable processes, and then determine their optical functions. The study in the dissertation is based on LC lenses with a hole-patterned electrode. To effectively exploit the incident light, a dropping-flow alignment method is used to achieve radially symmetric LC distributions in the cell, through which tunable LC lenses can be made as linearly polarization independent. A 7 mm-diameter LC lens is fabricated with a circular hole-patterned electrode; its focal lengths are tunable from infinite to 27.5 cm when voltages from 0 Vrms to 80 Vrms are applied.

博士
國立彰化師範大學
物理學系
102
This dissertation presents experimental practices conducted to study the effect of synthesis methods on the thermoelectric properties of n-type cobalt skutterudite. In this effort, wet chemical preparation procedures are adopted. The produced powders are characterized using x-ray diffraction pattern, scanning electron microscopy, Hall and density measurements. The Seebeck coefficient (thermopower), electrical and thermal conductivity measurements are performed for all the fabricated samples. Various reaction conditions have been carried out to stabilize the CoSb3 phase by modified polyol processes. The power factor of the parent CoSb3 is significantly enhanced via Ni substituting in Co site of Co4-xNixSb12 compounds (x= 0.0, 1.5ε, 2.5ε, 3.0ε, 4.0ε, and ε= 0.03125) synthesized by a rapid preparation procedure using modified polyol process. We have succeeded also in producing n-type CoSb3 using hydrothermal synthesis method. Different synthesis temperatures with reaction duration of time of 12 h are investigated to obtain the single phase of CoSb3. The remarkable low thermal conductivity of 1.33 - 1.46 Wm-1K-1 at room temperature is attained for the pristine CoSb3, which is comparable with or even lower than the filled CoSb3 obtained from solid state reaction. Enhancement of the power factor of CoSb3 samples synthesized using hydrothermal method is practiced via Ni-doping into the Co1-xNixSb3 structure with x=0.03215, 0.07 and 0.125. To study the effect of simultaneously electrons and holes doping on thermoelectric properties of CoSb3, we have succeeded in hydrothermally synthesizing co-doped Co1-x-yNixFeySb3 compounds with weighted compositions of {(x,y)}={(0.07,0.0), (0.07,0.03), (0.07,0.05), (0.14,0.10), (0.14,0.12), (0.14,0.14)}. The obtained results show thermal conductivity can be more reduced by co-doping of Ni and Fe, while the power factor is also enhanced. We have used solid state reaction to produce tungsten ditelluride. Based on the measured thermoelectric properties of produced WTe2 samples, we found it suitable candidate for investigating the thermoelectric properties of CoSb3 composite. As a result, the largest zT value of about 0.5 is achieved at 562 K for CoSb3 +yWTe2 composites for simultaneously y=3 and 12 wt. %. The In-filled InxCo4Sb12 compounds (x=0.25 and 0.50) are successfully produced using hydrothermal process combined with solid vapor reaction procedure. The largest room-temperature zT of 0.39 is attained for indium content, x=0.25. The thermal conductivity is reduced with increasing indium fillers. The density of InxCo4Sb12 bulks is increased markedly, which can confirm the insertion of In ions into the Sb-icosahedrons of Co4Sb12.

碩士
國立臺灣大學
物理研究所
93
In the liquid crystal display (LCD) industry, alignment of liquid crystal is done by conventionally rubbing method. Although this method is very simple and convenient, there will be dust particle and electric static charge left on polymer. Also the mechanism is still unknown. In 1972, Berreman suggested that the alignment of liquid crystal after rubbing treatment to the surface is because of the ultrafine grooving structure formed and alignment along the grooving structure would reach a minimum energy. In the thesis, we try to create a new liquid crystal alignment method based on Berreman’s theoretical model to produce ultrafine grooving structure to be the alignment layer of liquid crystal by electron beam lithography. This would also avoid problems induced during rubbing. It is shown that the newly-developed alignment method has great behavior of liquid crystal alignment. Then we try to measure the azimuthal anchoring energy of a liquid crystal cell made by such method to quantitatively judge the degree of alignment, and observe the relation between the grating pitch and the azimuthal anchoring energy. We also measure the optical properties such as V-T curves and the response time of the LC aligned by different pitches of grooves to characterize the groove alignment method.

碩士
國立臺灣科技大學
高分子系
98
This study of the use of synthetic lactic acid structures with double chiral centres liquid crystal (LC) material, in the experiment with polarized optical microscopy (POM) observation of the liquid crystal material from the isotropic temperature down to appear chiral smectic A phase (SmA*), it will produce the homeotropic texture of the LC phase; So, we hope that the SmA* phase LC materials by mixing photo-induced vertical alignment (VA) of the negative dielectric anisotropy LC (Nematic type LC)/acrylic monomer mixture systems, in order to auxiliary LC molecules to achieve the overall effect of the vertical arrangement of one of the main purpose of this experiments. The LC mixture systems in this VA mode, we observe the LC molecules arrangement condition by POM and the use of differential scanning calorimeter (DSC) to investigate the LC phase-transition behaviors. Finally, for the preliminary gray-scale characteristics of the LC mixture systems is also being explored.

碩士
國立臺北科技大學
光電工程系研究所
95
In this study, the photo-curable monomer, which was used to form vertical alignment, was doped into liquid crystal (E7) at various proper concentrations and injected into empty parallel-aligned cell, so called “OCB Cell” or “π-cell”. In order to accomplish the initial bend or twist configuration to reduce the “Warm Up Time” of the π-cell, it was suffered from UV irradiation to stabilized at high pretilt angle. Four parts were presented to discuss. Besides, due to the characteristics of the polymer, the polymer bundles mostly existed near the substrate. Therefore, there is good optical contrast because of light scattering free. We study the LC molecular alignment and electro-optical characteristics by observing the polarizing optical microscopy, voltage to transmission curve, phase retardation, response time and horizontal viewing angle. In addition, we verified the experimental results by simulation software “DIMOS”. We found that the higher pretilt angle could be accomplished by more curing time, larger curing voltage and higher polymer concentration. And we also discuss the electro-optical characteristics of the twist-π configuration. Although the experimental result were not we expected, it proved that LC molecules could be stabilized at various alignment configuration, including splay, twist and bend state.

碩士
國立臺灣科技大學
材料科學與工程系
104
The optimal preparation methods and the electro-optical properties of high contrast liquid crystal device by photo induce vertical alignment will be studied. In the study, the research use non-contact photo-polymerization induced liquid crystal (LC) and pre-polymer to form a vertical alignment (VA) effect of pseudo-Polymer thin film after the phase separation. In the molecular structure design, the research utilize photo-curable acrylic pre-polymer, (alkyl long carbon chain and main chain biphenol type etc.) and mix photo-initiator and negative dielectric anisotropy type liquid crystal (NLC) etc. component together. Forming the homogeneous LC mixture solution (NLC/photo-curable acrylic pre-polymer mixture systems) is via enough stirred and ultrasonic vibration. The research use photo-polymerization induced phase separation (PIPS) effect, and to make the NLC and the photo-curable acrylic pre-polymer generate composite layer structure of the vertical alignment copolymer film (VACOF) after the Ultra-Violet (UV) light irradiation process. The photo alignment of this novel technology can not only improve the traditional rubbing alignment shortcoming but also promote yield of the process. Our goal is expecting toward shortening the process for manufacture and decreasing the cost of the panel.

This thesis presents Raman study of 2D materials of contemporary interests: 2H-MoTe_2, type-II Weyl semimetal (T_d-MoTe_2), structurally anisotropic semiconductors (1T'-ReX_2 (X=S, Se)) and Mott insulator (FePS_3) under different conditions such of, high-pressure (up to 19 GPa), low-temperature (80 K), and electron/hole doping at carrier concentration of ∼ 10^13/cm^2. In-situ Raman measurements were carried out on electrochemically top-gated field-effect transistor (FET) devices with few-layer 2H-MoTe_2 as a channel, to probe the asymmetry of phonon coupling between electrons and holes. We also showed that the doped holes are localized in the top two layers of the nanocrystal. In addition, temperature-dependent Raman measurements were performed in few-layer 1T'-MoTe_2 to look for the Raman signatures of semiconductor to Weyl semimetallic transition. Phonon renormalization with electron doping in isostructural bilayer ReS_2 and trilayer ReSe_2 were done to highlight their different EPC. We showed that bilayer ReS_2 exhibits doping tunable Fano resonance as a result of its high EPC. In the last part of the thesis, high-pressure Raman experiments on bulk FePS_3 were carried out to gain insight into the Mott insulator to metal transition.

Biological processes at the cellular level take place in heterogeneous environments, and usually involve only a small number of molecules. They tend to exhibit strong time dependent fluctuations, as a result, and are, therefore, intrinsically stochastic. The present thesis describes some of the efforts I have made during the course of my research work to develop simple, analytically tractable models of a selection of biologically-inspired problems in which this kind of stochasticity is a central ingredient. These problems are: (i) single molecule enzyme activity (ii) intermittency in single enzymes, (iii) liquids crystal dynamics (iv) modulation of electron transfer kinetics during photosynthesis, and (v) anomalous polymer translocation dynamics. All of these problems can be defined in terms of quantity that changes randomly in time because of environmental fluctuations with broad distributions of relaxation times. In this thesis I show that a generalization of a model that describes simple Brownian Motion can be used to understand many of the dynamical aspects of these problems.

Biological processes at the cellular level take place in heterogeneous environments, and usually involve only a small number of molecules. They tend to exhibit strong time dependent fluctuations, as a result, and are, therefore, intrinsically stochastic. The present thesis describes some of the efforts I have made during the course of my research work to develop simple, analytically tractable models of a selection of biologically-inspired problems in which this kind of stochasticity is a central ingredient. These problems are: (i) single molecule enzyme activity (ii) intermittency in single enzymes, (iii) liquids crystal dynamics (iv) modulation of electron transfer kinetics during photosynthesis, and (v) anomalous polymer translocation dynamics. All of these problems can be defined in terms of quantity that changes randomly in time because of environmental fluctuations with broad distributions of relaxation times. In this thesis I show that a generalization of a model that describes simple Brownian Motion can be used to understand many of the dynamical aspects of these problems.

In this thesis, geometry is used as a basis for conducting experiments aimed at growing and arranging inorganic minerals on curved interfaces. Mineralisation is directed using crystalline and liquid-crystalline metallic soaps and surfactant/water systems as templates.¶ A review of the history, syntheses, structure and liquid crystallinity of metallic soaps and other amphiphiles is presented as a foundation to understanding the interfacial architectures in mesostructured template systems in general. ...