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The hydrophobic interaction refers to a mutually attractive force experienced by hydrophobic surfaces or molecules across water. At the molecular scale, it drives the selfassembly of lipid vesicles and micelles and accelerates interfacial chemical reactions. At the macroscale, it confers upon numerous plants and insects the ability to repel water and is harnessed in practical applications, such as water-proofing and desalination. However, despite its ubiquity and significance, mechanistic insights into the hydrophobic interaction between macroscopic surfaces remain unclear. A significant body of experimental data on surface force measurements exists, which were obtained following this protocol: hydrophobic molecules (typically organosilanes) are physisorbed onto molecularly smooth mica films that are glued onto transparent rigid silica discs and driven towards each other while measuring forces and distances. We developed a protocol for functionalizing mica surfaces with perfluorodecyltrichlorosilane (FDTS) to achieve robust, ultra-smooth hydrophobic surfaces. Then we investigated the consequences of nuclear quantum effects (NQEs) in water on the hydrophobic interaction. Whereas NQEs are known to influence physical and chemical properties of water, their impact on the hydrophobic interaction has remained largely unexplored. We find that the attractive forces between FDTS-coated mica surfaces were ~ 10% higher in light water (H2O) than in heavy water (D2O) even though macroscopic measurables, such as the interfacial tensions and contact angles are indistinguishable. This is the first-ever experimental demonstration of nuclear quantum effects at play in modulating hydrophobic surface forces. Towards practical applications, we investigated the partitioning of small, amphiphilic molecules onto our molecularly smooth FDTS-coated mica films. These scenarios are relevant in wastewater treatment, bioresource processing, fermenter broths, and food & beverage industries. Water-soluble short chain alcohols (ethanol) readily partitioned onto FDTS surfaces and remained attached onto the surface. The presence of alcohols was confirmed by surface force measurements, contact angle goniometry of water drops, and gas chromatography. We investigated protocols for characterizing fouled surfaces and cleaning them. These protocols were tested on realistic desalination membranes and proved effective. Thus, our findings could be used to develop robust protocols for characterizing membrane fouling and cleaning protocols in various separation processes.

Cette thèse porte sur l'étude des effets quantiques en dynamique moléculaire (DM). La DM est une méthode numérique qui permet l'étude des propriétés de la matière condensée. Cependant, la méthode étant basée sur la mécanique classique, les effets quantiques associés à la dynamique des noyaux, tels que l'énergie de point zéro ou l'effet tunnel, ne sont pas pris en compte. Ces effets quantiques nucléaires peuvent cependant jouer un rôle majeur, en particulier aux basses températures et/ou dans les systèmes contenant des atomes légers comme l'hydrogène. La dynamique moléculaire par intégrales de chemins (PIMD) est souvent utilisée, dans ce cas, pour tenir compte de la nature quantique des noyaux. Cette approche fournit des résultats quantiques exacts, mais son coût en temps de calcul élevé limite son domaine d'application. La méthode du bain thermique quantique (QTB) a été proposée comme une alternative à la PIMD. L'approche QTB est particulièrement intéressante car son coût en temps de calcul est équivalent à celui de la DM standard permettant ainsi l'étude de systèmes complexes et de plus grande taille.La première partie de cette thèse est consacrée à l'étude de la méthode QTB. Nous avons étudié le comportement de la méthode sur différents systèmes modèles afin d'étudier ses limites. En particulier, le problème du "zero point energy leakage" est étudié en détail et nous montrons que l'augmentation du coefficient de friction du QTB permet de limiter ce problème. Nous avons également développé une combinaison de la méthode QTB avec la méthode PIMD. Cette méthode combinée QTB-PIMD permet de réduire le coût en temps de calcul des simulations PIMD standards.Dans une deuxième partie, nous avons utilisé ces méthodes pour étudier la conduction de l'hydrogène dans des matériaux pérovskites. Nous nous intéressons d'abord à l'impact des effets quantiques sur la diffusion de l'hydrogène dans BaZrO3, un matériau d'électrolyte potentiel pour piles à hydrogène. L'hydrogène étant l'élément le plus léger, un impact important des effets quantiques est attendu. Nous trouvons que les effets quantiques sont effectivement importants à basse température, mais leur impact sur la diffusion reste faible aux températures de fonctionnement typiques des piles à hydrogène. Enfin, nous avons étudié les mécanismes de diffusion de l'hydrogène dans GdBaCo2O5.5. Nous mettons en évidence une diffusion anisotrope dans ce matériau et deux mécanismes principaux de diffusion. / This thesis deals with the study of quantum effects in molecular dynamics (MD). MD is a powerful numerical method to investigate the properties of condensed matter systems. However, since the method is based on classical mechanics, quantum effects associated with the dynamics of the nuclei, such as zero-point energy or tunnelling, are not taken into account. These nuclear quantum effects can, however, play a major role in particular at low temperatures and/or in systems containing light atoms such as hydrogen. In these cases, a standard way to account for the quantum nature of the nuclei is to use path integral molecular dynamics (PIMD). This method provides exact quantum results however its high computational cost limits its range of applicability. The quantum thermal bath (QTB) method has been proposed as an alternative to PIMD. The QTB method is particularly appealing because of its computational cost that is equivalent to standard MD thus allowing to study large and complex systems.The first part of this thesis is devoted to the study of the QTB method. We have studied the behavior of the method in selected model systems in order to investigate its limitations. We have focused, in particular, on the zero-point energy leakage problem and found that increasing the friction coefficient of the QTB can significantly limit this problem. We also have developed another way to use the QTB method by combining it with PIMD. This combined QTB-PIMD method allows, in particular, to decrease the computational cost of standard PIMD simulations.In a second part, we have used these methods to study hydrogen conduction in perovskite materials. We have first investigated the impact of quantum effects on the diffusion of hydrogen in BaZrO3, a potential electrolyte material for hydrogen fuel cells. Since hydrogen is the lightest element, we expect quantum effects to have a significant impact on its dynamics. We find that quantum effects are indeed significant at low temperatures although their impact on the diffusion remains low at the typical working temperatures of hydrogen fuel cells. Finally, we have investigated the diffusion mechanisms of hydrogen in GdBaCo2O5.5. We evidence that the diffusion is anisotropic in this material and two main diffusion mechanisms.

L’étude des effets quantiques nucléaires (NQE) suscite de plus en plus d’intérêt. En effet, les effets quantiques comme l’effet tunnel ou l’énergie de point zéro, peuvent profondément modifier les propriétés de matériaux constitués d'atomes légers comme l'hydrogène. Les méthodes standards de simulation des NQE sont basées sur les intégrales de chemin. Le bain thermique quantique (QTB) constitue une alternative à ces méthodes: le principe est que les degrés de liberté classiques du système obéissent à une équation de Langevin et sont couplés à des oscillateurs harmoniques quantiques. Dans l’équation de Langevin classique, la force aléatoire est un bruit blanc et le théorème de fluctuation-dissipation classique est vérifié; avec le QTB, le théorème de fluctuation-dissipation quantique est vérifié. Nous étudierons à travers des modèles simples la validité et les limites du QTB et montrerons qu'il permet de simuler des systèmes de la matière condensée en incluant les NQE en générant leurs propriétés structurales et dynamiques. Nous montrerons que le QTB est particulièrement adapté à l’étude de la symétrisation de liaisons hydrogènes et permet d'identifier précisément une pression de transition. Celle-ci dépend de la distance entre deux oxygènes voisins comme dans la glace sous haute pression, mais est modifiée par la présence d'impuretés ioniques ou par l'environnement atomique des liaisons hydrogènes comme dans la phase delta de AlOOH. De plus, en comparant des simulations classiques à des simulations QTB, nous pouvons identifier les rôles respectifs des effets quantiques et thermiques dans ces transitions de phase. / Increasing interest has risen for nuclear quantum effects (NQE) in the recent past. Indeed, NQE such as proton tunneling and zero point energy often play a crucial role in the properties of hydrogen-containing materials. The standard methods to simulate NQE are based on path integrals. An alternative to these methods is the Quantum Thermal Bath (QTB): it is based on a Langevin equation where the classical degrees of freedom are coupled to an ensemble of quantum harmonic oscillators. In the classical Langevin equation, the random force is a white noise and fulfills the classical fluctuation-dissipation theorem, while within the QTB formalism, it fulfills the quantum fluctuation-dissipation theorem. We investigate through simple models the reliability and the limits of the QTB and show that the QTB enables realistic simulations including NQE of condensed-phase systems, generating static and dynamic information such as pair correlation functions and vibrational spectra which can be confronted with experimental results. We show that the QTB is particularly successful in the study of the symmetrization of hydrogen bonds in several systems. Indeed, the difficulty lies in the identification of a precise transition pressure since this phase transition is often blurred by quantum or thermal fluctuations. In high-pressure ice, it depends on the oxygen-oxygen distance but it can be affected by ionic impurities and by the asymmetric environment of hydrogen bonds as in the delta phase of AlOOH. Moreover, by comparing results from QTB and standard ab initio simulations, we are able to disentangle the respective roles of NQE and thermal fluctuations in these phase transitions.

An increasing need for effective thermal sensors, together with dwindling energy resources, have created renewed interests in thermoelectric (TE), or solid-state, energy conversion and refrigeration using semiconductor-based nanostructures. Effective control of electron and phonon transport due to confinement, interface, and quantum effects has made nanostructures a good way to achieve more efficient thermoelectric energy conversion. This thesis studies the two well-known approaches: confinement and energy filtering, and implements improvements to achieve higher thermoelectric performance. The effect of confinement is evaluated using a 2D material with a gate and utilizing the features in the density of states. In addition to that, a novel controlled scattering approach is taken to enhance the device thermoelectric properties. The shift in the onset of scattering due to controlled scattering with respect to sharp features in the density of states creates a window shape for transport integral. Along with the controlled scattering, an effective utilization of Fermi window can provide a considerable enhancement in thermoelectric performance. The conclusion from the results helps in selection of materials to achieve such enhanced thermoelectric performance. In addition to that, the electron filtering approach is studied using the Wigner approach for treating the carrier-potential interactions, coupled with Boltzmann transport equation which is solved using Rode's iterative method, especially in periodic potential structures. This study shows the effect of rapid potential variations in materials as seen in superlattices and the parameters that have significant contribution towards the thermoelectric performance. Parameters such as period length, height and smoothness of such periodic potentials are studied and their effect on thermoelectric performance is discussed. A combination of the above two methods can help in understanding the effect of confinement and key requirements in designing a nanostructured thermoelectric device that has a enhanced performance.

In dieser Dissertation diskutiere ich theoretische Methoden zur Simulation von Grenzflächen zwischen Metallen und Molekülen auf atomarer Maßstabsebene, die für die Speicherung und Erzeugung "sauberer" Energie von Bedeutung sind, und wende sie an. Wir verwenden die Dichtefunktionaltheorie für das elektronische Subsystem und verschiedene Methoden wie die (quasi-)harmonische Näherung und die Pfadintegral-Molekulardynamik, um die Quanteneigenschaften des nuklearen Subsystems zu berücksichtigen. Wir berechnen den Isotopeneffekt auf die Arbeitsfunktion von Cyclohexan, das an der Rh(111)-Oberfläche adsorbiert wird, ein Effekt, der sich aus der Elektron-Phonon-Kopplung nur dann ergibt, wenn die nuklearen Freiheitsgrade quantenmechanisch behandelt werden. Deuteriertes Cyclohexan C6D12 hat einen größeren Adsorptionsabstand als gewöhnliches Cyclohexan. Pfadintegral-Molekulardynamiksimulationen zeigen auch eine temperaturabhängige Renormierung der elektronischen Zustandsdichte in diesem System. Schließlich befassen wir uns mit Oberflächenreaktionen auf einer geladenen metallischen Oberfläche. Wir stellen unsere Implementierung der Nudged-Elastic-Band-Methode (NEB) im i-PI-Paket vor und diskutieren ihre Leistungsfähigkeit. Anschließend setzen wir die Methode ein, um die Energiebarriere der Wasserspaltungsreaktion auf einer Pd(111)-Oberfläche zu berechnen, die einem elektrischen Feld unterschiedlicher Intensität ausgesetzt ist. Wir zeigen, dass die niedrigste Dissoziationsbarriere auftritt, wenn das Feld eine Stärke erreicht, die eine geometrische Frustration des auf der Oberfläche adsorbierten Wassermoleküls hervorruft, und dass die Nullpunktenergiebeiträge zur Barriere dieser Reaktion über den weiten Bereich der auf das System angelegten elektrischen Feldstärken nahezu konstant bleiben. Wir erklären dies durch eine gegenseitige Aufhebung der Rot- und Blauverschiebungen einzelner Schwingungsmoden zwischen Reaktant und Übergangszustand. / In this thesis, I discuss and apply theoretical methods for simulating interfaces between metals and molecules of relevance to "clean" energy storage and production on an atomistic scale. We use density-functional theory for the electronic subsystem and various methods such as (quasi-)harmonic approximation and path integral molecular dynamics to account for quantum properties of the nuclear subsystem, determining which methods are sufficient to grasp the essential phenomena while remaining computationally affordable. We calculate isotope effect on the work function of cyclohexane adsorbed on Rh(111) surface, an effect that emerges from electron-phonon coupling only when the nuclear degrees of freedom are treated quantum-mechanically. Deuterated cyclohexane C6D12 has larger adsorption distance than ordinary cyclohexane. Path integral molecular dynamics simulations also show a temperature-dependent renormalization of the electronic density of states in this system, induced by both thermal and quantum fluctuations of nuclei. Finally, we address surface reactions on a charged metallic surface. We present our implementation of the nudged elastic band (NEB) method in i-PI package and discuss its performance. We then employ the method to calculate the energy barrier of water splitting reaction on a Pd(111) surface subjected to electric fields of different strengths. We show that the lowest dissociation barrier takes place when the field reaches a strength that induces a geometric frustration of the water molecule adsorbed on the surface, and that the zero-point energy contributions to the barrier of this reaction remain nearly constant across the wide range of electric field strengths applied to the system. We explain this by a mutual cancellation of the red and blue shifts of individual vibrational modes between reactant and transition states.

Dans les dernières années, beaucoup de travail a été consacré par l’industrie électronique pour réduire la consommation d’énergie des composants micro-électroniques qui représente un fardeau important dans la spécification des nouveaux systèmes.Afin de réduire la consommation d’énergie, nombreuses stratégies peuvent être adoptées au niveau des systèmes micro-électroniques et des simples dispositifs nano-électroniques. Récemmentle Transistor Tunnel `a effet de champ (Tunnel-FET) s’est imposé comme un candidat possible pour remplacer les dispositifs MOSFET conventionnels pour applications de tr`es basse puissance à des tensions d’alimentation VDD < 0.5V. Nous présentons un modèle Multi-Subband Monte Carlo modifié (MSMC) qui a été adapté pour la simulation de TFET Ultra Thin Body Fully Depleted Seminconductor on Insulator (FDSOIUTB) avec homo- et hétéro-jonctions et des matériaux semi-conducteurs arbitraires. Nous prenons en considération la quantification de la charge avec une correction quantique heuristique mais précise, validée via des modèles quantiques complets et des résultats expérimentaux.Le modèle MSMC a été utilisé pour simuler et évaluer la performance de FD-SOI TFET sidéealisées avec homo- et hétéro-jonction en Si, alliages SiGe ou composés InGaAs. Dans la deuxième partie de l’activité de doctorat un travail de caractérisation à basse températurea été réalisé sur les TFETs en Si et SiGe homo- et hétéro-jonction fabriqués par le centre de recherche français du CEA -LETI. L’objectif est d’estimer la présence de l’effet Tunnel comme principal mécanisme d’injection et la contribution d’autres mécanismes d’injection comme le Trap Assisted Tunneling. / In the last years a significant effort has been spent by the microelectronic industry to reducethe chip power consumption of the electronic systems since the latter is becoming a majorlimitation to CMOS technology scaling.Many strategies can be adopted to reduce the power consumption. They range from thesystem to the electron device level. In the last years Tunnel Field Effect Transistors (TFET)have imposed as possible candidate devices for replacing the convential MOSFET in ultra lowpower application at supply voltages VDD < 0.5V. TFET operation is based on a Band-to-BandTunneling (BtBT) mechanism of carrier injection in the channel and they represent a disruptiverevolutionary device concept.This thesis investigates TFET modeling and simulation, a very challenging topic becauseof the difficulties in modeling BtBT accurately. We present a modified Multi Subband MonteCarlo (MSMC) that has been adapted for the simulation of Planar Ultra Thin Body (UTB)Fully Depleted Semiconductor on Insulator (FD-ScOI) homo- and hetero-junction TFET implementedwith arbitrary semiconductor materials. The model accounts for carrier quantizationwith a heuristic but accurate quantum correction validated by means of comparison with fullquantum model and experimental results.The MSMC model has been used to simulate and assess the performance of idealized homoandhetero-junction TFETs implemented in Si, SiGe alloys or InGaAs compounds.In the second part of the thesis we discuss the characterization of TFETs at low temperature.Si and SiGe homo- and hetero-junction TFETs fabricated by CEA-LETI (Grenoble,France) are considered with the objective to identify the possible presence of alternative injectionmechanisms such as Trap Assisted Tunneling. / Negli ultimi anni uno sforzo significativo `e stato speso dall’industria microelettronica per ridurreil consumo di potenza da parte dei sistemi microelettronici. Esso infatti sta diventando unadelle limitazioni pi`u significative per lo scaling geometrico della tecnologia CMOS.Diverse strategie possono essere adottate per ridurre il consumo di potenza considerando ilsistema microelettronico nella sua totalit`a e scendendo fino a giungere all’ottimizzazione delsingolo dispositivo nano-elettronico. Negli ultimi anni il transistore Tunnel FET (TFET) si`e imposto come un possibile candidato per rimpiazzare, in applicazioni a consumo di potenzaestremamente basso con tensioni di alimentazione inferiori a 0.5V, i transistori convenzionaliMOSFET. Il funzionamento del TFET si basa sul meccanismo di iniezione purament quantisticodel Tunneling da banda a banda (BtBT) e che dovrebbe permettere una significativa riduzionedella potenza dissipata. Il BtBT nei dispositivi convenzionali `e un effetto parassita, nel TFETinvece esso `e utilizzato per poter ottenere significativi miglioramenti delle performance sottosogliae pertanto esso rappresenta una nuova concezione di dispositivo molto innovativa erivoluzionaria.Questa tesi analizza la modellizazione e la simulazione del TFET. Questi sono argomenti moltocomplessi vista la difficolt`a che si hanno nel modellare accuratamente il BtBT. In questo lavoroviene presentata una versione modificata del modello di trasporto Multi Subband Monte Carlo(MSMC) adattato per la simulazione di dispositivi TFET planari Ultra Thin Body Fully DepletedSilicon on Insulator (UTB FD-SOI), implementati con un canale composto da un unicosemiconduttore (omogiunzione) o con differenti materiali semiconduttori (eterogiunzione). Ilmodello proposto tiene il conto l’effetto di quantizzazione dovuto al confinamento dei portatoridi carica, con un’euristico ma accurato sistema di correzione. Tale modello `e stato poivalidato tramite una comparazione con altri modelli completamente quantistici e con risultatisperimentali.Superata la fase di validazione il modello MSMC `e utilizzato per simulare e verificare le performancedi dispositivi TFET implementati come omo o eterogiunzione in Silicio, leghe SiGe,o composti semiconduttori InGaAs.Nella seconda parte della tesi viene illustrato un lavoro di caratterizazione di TFET planari abassa temperatura (fino a 77K). Sono stati misurati dispositivi in Si e SiGe a omo o eterogiuzioneprodotti nella camera bianca del centro di ricerca francese CEA-LETI di Grenoble. Tramite talimisure `e stato possibile identificare la probabile presenza di meccanismi di iniezione alternativial BtBT come il Tunneling assistito da trappole (TAT) dimostrando come questo effetto `e,con ogni probabilit`a, la causa delle scarse performance in sottosoglia dei dispositivi TFETsperimentali a temperatura ambiente.

臺灣在二十世紀中完成了人口轉型，特別是生育轉型的幅度與速度最為劇烈。也正因為生育轉型過於成功，臺灣此刻正面臨超低生育率導致的人口衰滅危機。近年來，人口學界針對生育率變遷，熱中於探討生育率的步調（tempo）與數量（quantum）效應，藉此瞭解時期生育率變遷的趨勢。 生育步調與數量的分析，本質上仍是時期性測量，未能真正瞭解年輪生育率的變遷，以致對於時期生育率趨勢的分析無法解決根本問題。這個現象，對於臺灣生育率研究特別必須加以處理。然而，臺灣雖然是人口資料的「寶庫」，有關生育的人口統計，卻只有存在於二十世紀下半葉，亦即，二十世紀前半葉的完整生育統計已經無法獲取。本研究試圖結合人口普查、戶籍統計，以及抽樣調查資料，運用參數式模型（parametric mode）和人口轉換（demographic translation）等人口分析方法，嘗試重建二十世紀完整的時期與年輪生育率，藉此，分析年輪生育率與時期生育率之間的變遷關係，最終瞭解未來生育率發展的可能後果。 / Demographic Transition has been completed during the middle of 20th century in Taiwan, and the extent and speed of transition are spectacularly rapid. Due to the over succeed of the demographic transition, lowest-low fertility pattern has stricken Taiwan society and probably led to a horrible extinction. Recently, in order to project the pattern of fertility rate, demographers endeavored to figure out how tempo and quantum effects contribute to fertility rate. Unfortunately, analysis of tempo and quantum effects is essentially periodic measurement. It leads no way to understand the pattern of cohort fertility in Taiwan. However, although Taiwan’s demographic statistics is well known as the world’s treasure trove, the fertility statistics are available for only 50 years. It means that we are not capable of having the first half 20th century’s fertility rate in Taiwan. We use demographic analytic methods such as parametric mode and demographic translation to analyze combined data which is constituted of census data, vital statistics, and survey data. The object of this research is to re-build the 20th century’s fertility rate in Taiwan. Once we have the intact fertility rate in 20th century, we could realize the pattern of period and cohort fertility transition. Furthermore, we will have a better chance to project Taiwan’s fertility rate in the future.

L’amélioration des performances du transistor MOS passe par la réduction de ses dimensions. Dans quelques années, la longueur de grille des dispositifs va descendre en dessous de 10 nm. A cette échelle, les effets quantiques deviennent prépondérants et dégradent considérablement les performances électriques des transistors à simple grille. Le transistor à nanofil avec grille enrobante est une architecture alternative intéressante pour augmenter le contrôle électrostatique du canal de conduction. Malgré les améliorations apportées par cette architecture, le courant à l’état bloqué reste perturbé par l’effet tunnel dans la direction source-drain. Afin de réduire ce courant sans réduire celui à l’état passant, nous avons étudié l’impact d’un rétrécissement local de la section transverse du canal coté drain (architecture notch-MOSFET). Pour cela, nous avons développé un simulateur 3D basé sur le formalisme des fonctions de Green hors équilibre couplé de façon auto-cohérente avec l’équation de Poisson. Ces calculs sont effectués dans l’approximation de la masse effective. Nous avons ensuite étudié le transport des trous dans les transistors à nanofil de type p, ainsi que l’influence d’une impureté ionisée dans le canal de ces dispositifs. La complexité de la bande de valence a nécessité la mise en œuvre d’un modèle k&#8729;p à 6 bandes inclus dans le simulateur 3D évoqué précédemment. / Performances improvement of MOS transistors involves reduction of its dimensions. In a few years, the gate length of devices will reach sub-10 nm regime. At this scale, quantum effects become preponderant and considerably degrade electric performances of simple-gate transistors. The Gate-all-around nanowire transistor is an interesting alternative architecture to improve electrostatic control of the conduction channel. Despite the improvements made thanks to this architecture, the OFF-current remains disturbed by tunneling effect in source-drain direction. In order to decrease this current without decreasing the ON-current, we have studied the impact of local narrowing of transverse cross-section in drain side of the channel (notch-MOSFET architecture). To this purpose, we have developed a 3D simulator based on Non-equilibrium Green function formalism coupled self-consistently with Poisson equation. These simulations are performed in the effective mass approximation. Then we have studied holes transport in p-type nanowire transistors and the influence of an ionized impurity in the channel of these devices. The valence band complexity required six-band k&#8729;p model development include into previously mentioned 3D simulator.