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Adsorption is a ubiquitous phenomenon that plays key roles in numerous applications including molecule separation, energy storage, catalysis, and lubrications. Since adsorption is sensitive to molecular details of adsorbate molecule and adsorbent materials, it is often difficult to describe theoretically. Molecular modeling capable of resolving physical processes at atomistic scales is an effective method for studying adsorption. In this dissertation, the adsorption of small molecules in three emerging materials systems: porous liquids, room-temperature ionic liquids, and atomically sharp electrodes immersed in aqueous electrolytes, are investigated to understand the physics of adsorption as well as to help design and optimize these materials systems. Thermodynamics and kinetics of gas storage in the recently synthesized porous liquids (crown-ether-substituted cage molecules dispersed in an organic solvent) were studied. Gas molecules were found to store differently in cage molecules with gas storage capacity per cage in the following order: CO2>CH4>N2. The cage molecules show selectivity of CO2 over CH4/N2 and demonstrate capability in gas separation. These studies suggest that porous liquids can be useful for CO2 capture from power plants and CH4 separation from shale gas. The effect of adsorbed water on the three-dimensional structure of ionic liquids [BMIM][Tf2N] near mica surfaces was investigated. It was shown that water, as a dielectric solvent and a molecular liquid, can alter layering and ordering of ions near mica surfaces. A three-way coupling between the self-organization of ions, the adsorption of interfacial water, and the electrification of the solid surfaces was suggested to govern the structure of ionic liquid near solid surfaces. The effects of electrode charge and surface curvature on adsorption of N2 molecules near electrodes immersed in water were studied. N2 molecules are enriched near neutral electrodes. Their enrichment is enhanced as the electrode becomes moderately charged but is reduced when the electrode becomes highly charged. Near highly charged electrodes, the amount of N2 molecules available for electrochemical reduction is an order of magnitude higher near spherical electrodes with radius ~1nm than near planar electrodes. The underlying molecular mechanisms are elucidated and their implications for development of electrodes for electrochemical reduction of N2 are discussed. / Doctor of Philosophy / Adsorption is a ubiquitous phenomenon that plays key roles in numerous applications including molecule separation, energy storage, catalysis, and lubrications. Since adsorption is sensitive to molecular details of adsorbate molecule and adsorbent materials, it is often difficult to describe theoretically. Molecular modeling capable of resolving physical processes at atomistic scales is an effective method for studying adsorption. In this dissertation, the adsorption of small molecules in three emerging materials systems: porous liquids, room-temperature ionic liquids, and atomically sharp electrodes immersed in aqueous electrolytes, are investigated to understand the physics of adsorption as well as to help design and optimize these materials systems. Thermodynamics and kinetics of gas storage in the recently synthesized porous liquids (crown-ether-substituted cage molecules dispersed in an organic solvent) were studied. Gas molecules were found to store differently in cage molecules with gas storage capacity per cage in the following order: CO2>CH4>N2. The cage molecules show selectivity of CO2 over CH4/N2 and demonstrate capability in gas separation. These studies suggest that porous liquids can be useful for CO2 capture from power plants and CH4 separation from shale gas. The effect of adsorbed water on the three-dimensional structure of ionic liquids [BMIM][Tf2N] near mica surfaces was investigated. It was shown that water, as a dielectric solvent and a molecular liquid, can alter layering and ordering of ions near mica surfaces. vi A three-way coupling between the self-organization of ions, the adsorption of interfacial water, and the electrification of the solid surfaces was suggested to govern the structure of ionic liquid near solid surfaces. The effects of electrode charge and surface curvature on adsorption of N2 molecules near electrodes immersed in water were studied. N2 molecules are enriched near neutral electrodes. Their enrichment is enhanced as the electrode becomes moderately charged but is reduced when the electrode becomes highly charged. Near highly charged electrodes, the amount of N2 molecules available for electrochemical reduction is an order of magnitude higher near spherical electrodes with radius ~1nm than near planar electrodes. The underlying molecular mechanisms are elucidated and their implications for development of electrodes for electrochemical reduction of N2 are discussed.

Biomedical devices play a crucial role in the healthcare system, enabling more effective treatments, less invasive procedures, and more precise diagnoses. Due to these compelling reasons, development of new biomedical devices and biomaterials have always been in high demand. Exploring and refining fabrication methods are essential to the development of new biomedical devices. Some of the common fabrication methods include microfabrication methods (photolithography and soft lithography), 3D printing (additive manufacturing), laser machining, thermal drawing, and electrospinning. The choice of fabrication methods heavily depends on the materials, geometry, and functionalities of biomedical devices. Currently, the thermal drawing process has proven to be an excellent scalable fabrication platform for neural interface, tissue engineering, tumor/cancer treatment, soft robotics, and smart textiles. This Ph.D. dissertation summarizes my research on the fabrication and validation of thermally drawn multifunctional polymer fiber probes for modern biomedical applications, primarily in the fields of neural interfaces and tumor treatments. Understanding the neural basis of behavior requires monitoring and manipulating combinations of physiological elements and their interactions in behaving animals. Utilizing the thermal drawing process, we developed T-DOpE (Tapered Drug delivery, Optical stimulation, and Electrophysiology) probes and Tetro-DOpE (Tetrode-like Drug delivery, Optical stimulation, and Electrophysiology) probes that can simultaneously record and manipulate neural activity in behaving rodents. Taking advantage of the triple-functionality, we monitored local field potential (LFP) while manipulating cannabinoid receptors (CB1R; microfluidic agonist delivery) and CA1 neuronal activity using optogenetics. Focal infusion of CB1R agonist downregulated theta and sharp wave-ripple oscillations (SPW-Rs). Furthermore, we found that CB1R activation reduces sharp wave-ripples by impairing the innate SPW-R-generating ability of the CA1 circuit. Microscale electroporation devices are mostly restricted to in vitro experiments (i.e., microchannel and microcapillary). We developed a flexible microscale electroporation fiber probe through a thermal drawing process and femtosecond laser micromachining techniques. The novel fiber microprobes enable microscale electroporation and arbitrarily select the cell groups of interest to electroporate. Successful reversible and irreversible microscale electroporation was observed in a 3D collagen scaffold (seeded with U251 human glioma cells) using fluorescent staining. Leveraging the scalable thermal drawing process, we envision a wide distribution of multifunctional polymer fiber probes in research facilities and hospitals. Along with the fiber probes presented in this dissertation, additional insight and future perspective on thermally drawn biomedical devices are discussed. / Doctor of Philosophy / The thermal drawing process is a versatile and scalable platform for fabricating functional fiber technology. The process was formerly adapted from fabrication method for silica optical fibers, widely used in telecommunication (e.g., telephone, internet, cable TV, etc.). To name some functionalities of these fibers, they can move, hear, sense touch, change colors, harvest and store energy, record and manipulate brain activity, and ablate tumors. As imagined, these functionalities are derived from the unique geometry and functional materials embedded along the fiber. Therefore, developing the fiber design tailored to a specific application is a critical step to making a successful fiber product. In this dissertation, I will present my work on biomedical devices fabricated with the thermal drawing process and their application in neuroscience and tumor/cancer treatment. Utilizing the thermal drawing process, we developed neural interfaces that can be implanted into the deep brain and record and simultaneously manipulate the neural activity. These neural interfaces (Chapter 2,3; T-DOpE and Tetro-DOpE probes, respectively) are able to record both local field potentials (LFP; activity of thousands or more neurons) and single action potentials (single on/off signal from individual neurons nearby). By manipulating the gene expression, we can control the activity of neurons with specific light (λ= 470nm; blue light) exposure. We implemented optical waveguide in our probes to guide light from a laser source to the tip of the probe and manipulate the neural activity. Furthermore, we fabricated micro-channels within the device to enable focal drug delivery at the tip of the device. Using the T-DOpE probe, we studied the effect of local synthetic cannabinoid injection in the hippocampus. We found that the local injection of the drug in hippocampus CA1 makes neurons incapable of generating sharp wave-ripples (a neural signal associated with memory). Electroporation is a biophysical phenomenon where short high electric field pulses introduce nanoscale defects in cell membrane. These defects can cause unstable cellular homeostasis and eventually leads to cell death. Due to reduced treatment time, no heat effect, and tissue selectivity, electroporation has been used in clinical trials for cancer treatments. Using the thermal drawing process and laser micromachining techniques, we developed a flexible microscale electroporation fiber probe capable of ablating tumor cells. Due to the low-cost and scalability of thermal drawing process, we envision the use of thermally drawn functional fiber technology in biomedical fields. In this dissertation, I also address some challenges and future directions of thermally drawn functional fibers in biomedical fields.

We investigate non-geometric sharp permutation groups of type {0,k} whose point stabilizers are certain Frobenius groups. We show that if a point stabilizer has a cyclic Frobenius kernel whose order is a power of a prime and Frobenius complement cyclic of prime order, then the point stabilizer is isomorphic to the symmetric group on 3 letters, and there is up to permutation isomorphism, one such permutation group. Further, we determine a significant structural description of non-geometric sharp permutation groups of type {0,k} whose point stabilizers are Frobenius groups with elementary abelian Frobenius kernel K and Frobenius complement L with |L| = |K|-1. As a result of this structural description, it is shown that the smallest non-solvable Frobenius group cannot be a point stabilizer in a non-geometric sharp permutation group of type {0,k}.

Eine einzigartige experimentelle Beobachtung, welche die Basis für eine ganzheitliche, neurowissentschafliche Theorie für Gedächtnis darstellen könnte, sind sharp wave-ripples (SWRs). SWRs werden in lokalen Neuronennetzwerken erzeugt und sind wichtig für Gedächtniskonsolidierung; SWRs sind charakteristische Ereignisse der lokalen Feldpotentiale im Hippocampus des Säugetiers, die in Phasen von Schlaf und Ruhe vorkommen. Eine SWR besteht aus einer sharp wave, einer ≈ 100 ms langen Auslenkung des Feldpotentials, welche mit ripples, 110–250 Hz Oszillationen, überlagert ist. Jüngste Experimente bekräftigen die Theorie, dass ripples in Netzwerken inhibitorischer Interneurone (INT-INT) erzeugt werden, die aus parvalbumin-positive basket cells (PV+BCs) bestehen. PV+BCs sind untereinander über rekurrente inhibitorische Synapsen und Gap Junctions (GJs) gekoppelt. In dieser Arbeit untersuche ich die spezifische Funktion von interneuronalen Gap Junctions in ripples. Im Hauptteil dieser Arbeit demonstriere ich, dass GJs in INT-INT Netzwerken die neuronale Synchronität und die Feuerrate während ripples erhöhen, die ripple-Frequenz sich hingegen nur leicht verändert. Zusätzlich zeige ich, dass diese rippleunterstützenden Effekte nur dann auftreten, wenn die GJ-Transmission schnell genug ist (≈< 0.5 ms), was wiederum somanahe Kopplung voraussetzt (≈< 100 µm). Darüber hinaus zeige ich, dass GJs die oszillatorische Stärke der ripples erhöhen und so die minimale für ripples notwendige Netzwerkgröße verringern. Abschließend zeige ich, dass ausschließlich mit Gap Junctions gekoppelte INT-INT Netzwerke zwar mit ripple Frequenz oszillieren können, aber wahrscheinlich nicht der Erzeuger von experimentell beobachteten ripple-artigen Oszillationen sind. Zusammengenommen zeigen meine Resultate, dass schnelle Gap Junction-Kopplung von Interneuronen die Entstehung von ripples begünstigt und somit SWRs unterstützt, welche einen wichtigen Beitrag zur Bildung unserers Gedächtnisses leisten. / A unique experimental observation that opens ways for a holistic, bottom-up theory for memory generation are sharp-wave ripples (SWRs). SWRs are generated in local neuronal networks and are important for memory consolidation. SWRs are prominent features of the extracellular field potentials in the mammalian hippocampus that occur during rest and sleep; they are characterized by sharp waves, ≈ 100 ms long voltage deflections, that are accompanied by ripples, i.e., 110–250 Hz oscillations. Recent experiments support the view that ripples are clocked by recurrent networks of inhibitory interneurons (INT-INT), which are likely constituted by networks of parvalbumin-positive basket cells (PV+BCs). PV+BCs are not only recurrently coupled by inhibition but also by gap junctions (GJs). In this thesis, I investigate the specific function of interneuronal GJs in hippocampal ripples. Consequently, I simulate INT-INT networks and demonstrate that gap junctions increase the neuronal synchrony and firing rates during ripple oscillations, while the ripple frequency is only affected mildly. I further show that GJs only have these supporting effects on ripples when they are sufficiently fast (≈< 0.5 ms), which requires proximal GJ coupling (≈< 100 µm). Additionally, I find that gap junctions increase the oscillatory power of ripple oscillations and by this means reduce the minimal network size required for INT-INT networks to generate ripple oscillations. Finally, I demonstrate that exclusively GJ-coupled INT-INT networks can oscillate at ripple frequency, however, are unlikely the generator of experimentally observed ripple-like oscillations. In sum, my results show that fast interneuronal gap junction coupling promotes the emergence of ripples and hereby supports SWRs, which are important for the formation of memory.

Der Hippokampus spielt eine wichtige Rolle bei der Erfassung, Festigung und dem Wiederabrufen von Gedächtnisinhalten. Diese Prozesse werden von Oszillationen begleitet, die synchronisierte neuronale Aktivität wiederspiegeln. Der erste Teil dieser Arbeit konzentriert sich auf ‘ripples’, eine schnell schwingende Netzwerkaktivität, die an der Festigung von Gedächtnisinhalten beteiligt ist. Das Subikulum ist eine der Hauptausgangsstationen des Hippokampus und überträgt Informationen zu Zielregionen außerhalb dieser Region. Um dies besser zu verstehen, habe ich hier die Eigenschaften von subikulären Pyramidenzellen und deren Regulierung während ripples untersucht. Es zeigte sich, dass eine Untergruppe von Zellen, burst (in Salven) feuernde Zellen, ihre Aktivität erhöht, während eine zweite Untergruppe, regulär feuerende Zellen, ihre Aktivitaet während ripples vermindert. Ferner ist bei regulär feuernden Zellen das Verhältnis zwischen Inhibition und Exzitation höher als bei burst feuernden Zellen. Zusammen mit Erkenntnissen aus früheren Studien lassen diese Ergebnisse vermuten, dass Information während ripples hauptsächlich zu Zielregionen der burst feuernden Zellen geleitet wird. Neben Pyramidenzellen beherbergt der Hippokampus auch eine Vielzahl verschiedener Interneurone. Im zweiten Teil dieser Arbeit habe ich O-LM Interneurone der hippokampalen Region CA1 untersucht. Diese spielen eine wichtige Rolle bei der Kontrolle von Eingängen aus dem entorhinalen Kortex. Wir konnten zeigen, dass die exzitatorische Übertragung auf O-LM Interneurone durch Serotonin, einem von den Raphe-Kernen ausgeschütteten Neuromodulator, vermindert wird. Dies geschieht durch einen präsynaptischen Mechanismus, der wahrscheinlich eine Verminderung des Kalziumeinstroms in präsynaptische Endigungen umfasst. Eine Verminderung der Aktivität von O-LM Interneuronen durch Serotonin könnte die synaptische Übertragung von Signalen aus dem entorhinalen Kortex auf CA1 Pyramidenzelldendriten erleichtern. / The hippocampus plays an important role in the acquisition, consolidation and retrieval of memory. These processes are accompanied by hippocampal oscillations, which reflect synchronized neuronal activity. The first part of this thesis focuses on ripples, a fast oscillatory activity which is involved in memory consolidation. The subiculum as one of the main output areas of the hippocampus is ideally suited to mediate information transfer to extrahippocampal targets. Here I investigated the properties of subicular pyramidal cells and their modulation during ripples. I found that a subset of subicular pyramidal cells increases its firing rate during ripples whereas another subset decreases its firing rate. Furthermore I was able to identify a correlate between modulation and cell subtype: burst firing cells increased their firing rate, and regular firing cells decreased their firing rate. We could further show that regular firing cells receive a higher ratio of inhibition to excitation as compared to burst firing cells. Together with earlier work, these results suggest that information transferred during ripples is likely to be routed preferentially to target regions of the burst firing subtype. Besides pyramidal cells, the hippocampus hosts a variety of interneuron types. The second part of this thesis focuses on GABAergic O-LM interneurons of hippocampal area CA1, which play an important role in controlling input from the entorhinal cortex. We could show that excitatory transmission from local pyramidal cells onto O-LM interneurons is decreased by serotonin, a neuromodulator released from the midbrain raphe nuclei. This modulation is mediated by a presynaptic mechanism and is likely to involve a decrease in calcium influx into presynaptic terminals. We conclude that serotonin, by decreasing O-LM output, might release fibers from entorhinal cortex impinging onto CA1 pyramidal cell dendrites from inhibition.

Hippokampale Sharp Wave-Ripples (SWRs) sind elektrografische Ereignisse, die für die Konsolidierung von Erinnerungen eine Rolle spielen. Eine SWR ist durch eine schnelle Oszillation (>90 Hz, ''ripple'') charakterisiert, die sich mit der langsameren ''sharp wave'' ( / Hippocampal sharp wave-ripples (SWRs) are electrographic events that have been implicated in memory consolidation. A SWR is characterized by a fast (> 90 Hz) oscillation, the ripple, superimposed on a slow (< 30 Hz) sharp wave. In vivo, the fast component can express frequencies either in the ripple range (140-200 Hz) or fast-gamma range (90-140 Hz). Episodes in both bands exhibit intra-ripple frequency accommodation (IFA). In vitro, ripples are frequency-resistant to GABA modulators. These features constrain the type of mechanisms underlying the generation of the fast component. A prominent hypothesis proposes that a recurrent network of parvalbumin-immunoreactive basket cells (PV+BC) is responsible of setting the ripple frequency. The focus of the present thesis is on testing to which extent the PV+BC network can account for the aforementioned features of SWRs, which remain unexplained. Here, I simulated and analyzed a physiologically constrained in silico model of the PV+BC network in CA1 under different conditions of excitatory drive. The response of the network to transient excitation exhibits both IFA in the ripple band and frequency resistance to GABA modulators. The expression of IFA in the fast gamma band requires the involvement of pyramidal cells in a closed loop with the PV+BC network. The model predicts a peculiar relationship between the instantaneous frequency of ripples and the time course of the excitatory input to CA1. This prediction was confirmed in an in vitro model of SWRs. Additionally, I study the involvement of oriens lacunosum-moleculare interneurons (O-LM) during SWRs in vitro. I characterize the excitatory currents received by O-LM cells during SWRs and investigate the factors that determine their recruitment.

Nous avons étudié l'effet d'une réaction chimique sur le transfert de matière pour des systèmes à deux phases sous écoulement. La phase continue est une phase fluide et la phase dispersée est constituée de particules de catalyseur au sein desquelles une réaction chimique irréversible de premier ordre a lieu. Le soluté réactif est transporté par l'écoulement externe de fluide et pénètre dans la particule par diffusion, il se produit alors une réaction chimique qui consomme cette espèce. Nous modélisons le problème par un couplage interne-externe des équations de bilan et au moyen de deux conditions limites de raccordement: continuité de la concentration et équilibre des flux de masse à la surface des particules. Le cas d'une seule sphère isolée est traitée en premier lieu de manière théorique et numérique. Nous proposons un modèle pour prédire le coefficient de transfert de masse (nombre de Sherwood «réactif») en tenant compte de la convection-diffusion externes et du couplage diffusion-réaction internes. Nous validons le modèle en le comparant à des simulations numériques directes pleinement résolues (DNS boundaryfitted) sur un maillage adapté à la géométrie des particules. Pour la simulation de systèmes multiparticules, nous mettons en œuvre une méthode d'interface «Sharp» pour traiter les fronts raides de concentration. Nous validons la mise en œuvre de la méthode sur des solutions analytiques existantes en cas de diffusion, de diffusion-réaction et par comparaison avec des corrélations de convection-diffusion disponibles dans la littérature. Dans le cas d'une réaction chimique en présence de convection-diffusion, nous validons la méthode et nous évaluons sa précision en comparant avec les simulations pleinement résolues de référence. Ensuite, nous étudions le problème de l'écoulement et du transfert autour de trois sphères alignées soumis à une réaction chimique interne. Nous proposons un modèle de nombre de Sherwood «réactif» en complément d'une prédiction de transfert pour chaque sphère disponible dans la littérature. Nous validons le modèle par comparaison avec des simulations numériques directes pour une large gamme de paramètres adimensionels. Ensuite, nous étudions la configuration du lit fixe de particules de catalyseur. Nous modélisons le profil de concentration moyenne, en tenant compte de la réaction chimique dans le lit et les profils de concentration moyenne surfacique et volumique des particules. Nous introduisons un modèle pour le nombre de Sherwood «réactif» qui est comparé à des simulations numériques pour en évaluer les limites de validité / We studied the effect of a first order irreversible chemical reaction on mass transfer for two-phase flow systems in which the continuous phase is a fluid and the dispersed phase consists in catalystspherical particles. The reactive solute is transported by the fluid flow and penetrates through the particle surface by diffusion. The chemical reaction takes place within the bulk of the particle. Wehandle the problem by coupling mass balance equations for internal-external transfer with two boundary conditions: continuity of concentration and mass flux at the particle surface. We start with the case of a single isolated sphere. We propose a model to predict mass transfer coefficient (`reactive' Sherwood number) accounting for the external convection-diffusion along with internal diffusion-reaction. We validate the model through comparison with fully resolved Direct Numerical Simulations (DNS) performed by means of a boundary-fitted mesh method. For the simulation of multi-particle systems, we implemented a Sharp Interface Method to handle strong concentration gradients. We validate the implementation of the method thoroughly thanks to comparison with existing analytical solutions in case of diffusion, diffusion-reaction and by comparison with previously established correlations for convection-diffusion mass transfer. In case of convectiondiffusion- reaction, we validate the method and we evaluate its accuracy through comparisons with single particle simulations based on the boundary-fitted method. Later, we study the problem of three aligned-interacting spheres with internal chemical reaction. We propose a `reactive' Sherwood number model based on a known non-reactive prediction of mass transfer for each sphere. We validate the model by comparison with direct numerical simulations for a wide range of dimensionless parameters. Then, we study the configuration of a fixed bed of catalyst particles. We model the cup-mixing concentration profile, accounting for chemical reaction within the bed, and the mean surface and volume concentration profiles of the particles. We introduce a model for `reactive' Sherwood number that accounts for the solid volume fraction, in addition to the aforementioned effects. We compare the model to numerical simulations to evaluate its limitations

This is a report founded on a project by Atlas Copco called NYSTAB.  The application Nystab is a calculation program that can calculate the stability of the rockdrill-rigs made by Atlas Copco. The original version of Nystab is stored in a database from 1997 and the code is made in an old version of Visual Basic. My assignment was to develop the application in to a newer programming environment and make it last better in the upcoming years. The software I decided to use to accomplish this project is C# .NET in Visual Studio and Microsoft Access 2010. All the code is written in C# with some insertions from ADO.NET which helped me to easier connect the code with the database. The coding part was split into two pieces; the first was to develop the application scale done with Windows Forms, the second was to write the code for calculations in the application. This report will cover some methods of how you can connect the database to an application and why Microsoft Access was the best alternative for database in this project. The report also shows the difference between VB and C# to get an overview on why  people today often chose to develop their applications in C#. Exceptions is a big part of the handling of errors or search for errors in the application and the report shows concrete examples on how you use exceptions in different situations and why. / Detta är en rapport grundat på ett projekt för Atlas Copco vid namn NYSTAB. Programmet är ett beräkningsprogram som kan beräkna stabiliteten av Atlas Copcos borr-riggar, det ursprungliga programmet ligger på en databas från 1997 och är kodat i en gammal variant av Visual Basic. Mitt uppdrag var att utveckla programvaran till en nyare miljö med bättre framtidssäkerhet och kompabilitet samt att sätta mig in i Visual Basic miljön för att kunna få fram information om hur dessa stabilitetsberäkningar utförs. Den programvara jag har valt att arbeta i under detta projekt är C# .NET i Visual studio 2010 samt Microsoft Access 2010. All programmering är gjord i C# med inlägg från ADO.NET som hjälpt mig att koppla programmet med databasen. Programmeringen var uppdelad i två delar; dels skulle jag utforma en applikation som jag gjort med hjälp av Windows Forms och dels var det programmeringen av beräkningarna. Rapporten tar upp metoder att koppla databaser mot applikationer och varför Microsoft Access är den bästa databasen till just det här arbetet. Rapporten tar även upp skillnader mellan VB och C# för att få en överblick till varför man idag ofta väljer att programmera i C#. Exceptions är en stor del i felhanteringen eller felsökningsfunktionen i applikationen och rapporten tar upp konkreta exempel på hur man använder sig av exceptions i olika situationer och varför man gör detta.

The change of the spontaneous polarization due to a change of temperature is known as the pyroelectric effect and is restricted to crystalline, non-centrosymmetric and polar matter. Its main application is the utilization in infrared radiation sensors, but usage for waste heat energy harvesting or chemical catalysis is also possible. A precise quantification, i.e. the measurement of the pyroelectric coefficient p, is inevitable to assess the performance of a material. Hence, a comprehensive overview is provided in this work, which summarizes and evaluates the available techniques to characterize p. A setup allowing the fully automated measurement of p by utilizing the Sharp-Garn method and the measurement of ferroelectric hysteresis loops is described. It was used to characterize and discuss the behavior of p with respect to the temperature of the doped bulk III-V compound semiconductors gallium nitride and aluminum nitride and thin films of doped hafnium oxide, as reliable data for these materials is still missing in the literature. Here, the nitride-based semiconductors show a comparable small p and temperature dependency, which is only slightly affected by the incorporated dopant, compared to traditional ferroelectric oxides. In contrast, p of HfO2 thin films is about an order of magnitude larger and seems to be affected by the present dopant and its concentrations, as it is considered to be responsible for the formation of the polar orthorhombic phase.:1. Motivation and Introduction 2. Fundamentals 2.1. Dielectrics and their Classification 2.2. Polarization 2.3. Pyroelectricity 2.4. Ferroelectricty 2.5. Phase Transitions 2.6. Applications and Figures of Merit 3. Measurement Methods for the Pyroelectric Coefficient 3.1. General Considerations 3.1.1. Heating Concepts 3.1.2. Thermal Equilibrium 3.1.3. Electric Contact 3.1.4. Separation of Contributions 3.1.5. Thermally Stimulated Currents 3.2. Static Methods 3.2.1. Charge Compensation Method 3.2.2. Hysteresis Measurement Method 3.2.3. Direct Electrocaloric Measurement 3.2.4. Flatband Voltage Shift 3.2.5. X-ray Photoelectron Spectroscopy Method 3.2.6. X-ray Diffraction and Density Functional Theory 3.3. Dynamic Methods 3.3.1. Temperature Ramping Methods 3.3.2. Optical Methods 3.3.3. Periodic Pulse Technique 3.3.4. Laser Intensity Modulation Methods 3.3.5. Harmonic Waveform Techniques 4. Pyroelectric and Ferroelectric Characterization Setup 4.1. Pyroelectric Measurement Setup 4.1.1. Setup and Instrumentation 4.1.2. Automated Sharp-Garn Evaluation of Pyroelectric Coefficients 4.1.3. Further Examples 4.2. Hysteresis Loop Measurements 4.2.1. Instrumentation 4.2.2. Measurement and Evaluation 4.2.3. Examples 5. Investigated Material Systems 5.1. III-Nitride Bulk Semiconductors GaN and AlN 5.1.1. General Structure and Spontaneous Polarization 5.1.2. Applications 5.1.3. Crystal Growth and Doping 5.1.4. Pyroelectricity 5.2. Hafnium Oxide Thin Films 5.2.1. General Structure and Applications 5.2.2. Polar Properties in Thin Films 5.2.3. Doping Effects 5.2.4. Pyro- and Piezoelectricity 6. Results 6.1. The Pyroelectric Coefficient of Free-standing GaN and AlN 6.1.1. Sample Preparation 6.1.2. Pyroelectric Measurements 6.1.3. Lattice Influence 6.1.4. Slope Differences 6.2. Pyroelectricity of Doped Hafnium Oxide 6.2.1. Sharp-Garn Measurement on Thin Films 6.2.2. Effects of Silicon Doping 6.2.3. Dopant Comparison 7. Summary and Outlook A. Pyroelectric Current and Phase under Periodic Thermal Excitation B. Loss Current Correction for Shunt Method C. Conductivity Correction D. Comparison of Pyroelectric Figures of Merit Bibliography Publication List Acknowledgments / Die Änderung der spontanen Polarisation durch eine Änderung der Temperatur ist bekannt als der pyroelektrische Effekt, welcher auf kristalline, nicht-zentrosymmetrische und polare Materie beschränkt ist. Er findet vor allem Anwendung in Infrarot-Strahlungsdetektoren, bietet aber weitere Anwendungsfelder wie die Niedertemperatur-Abwärmenutzung oder die chemische Katalyse. Eine präzise Quantifizierung, d. h. die Messung des pyroelektrischen Koeffizienten p, ist unabdingbar, um die Leistungsfähigkeit eines Materials zu bewerten. Daher bietet diese Arbeit u.a. einen umfassenden Überblick und eine Bewertung der verfügbaren Messmethoden zur Charakterisierung von p. Weiterhin wird ein Messaufbau beschrieben, welcher die voll automatisierte Messung von p mit Hilfe der Sharp-Garn Methode und auch die Charakterisierung der ferroelektrischen Hystereseschleife ermöglicht. Aufgrund fehlerender Literaturdaten wurde dieser Aufbau anschließend genutzt, um den temperaturabhängigen pyroelektrischen Koeffizienten der dotierten III-V-Verbindungshalbleiter Gallium- und Aluminiumnitrid sowie dünner Schichten bestehend aus dotiertem Hafniumoxid zu messen und zu diskutieren. Im Vergleich zu klassichen ferroelektrischen Oxiden zeigen dabei die nitridbasierten Halbleiter einen geringen pyroelektrischen Koeffizienten und eine kleine Temperaturabhängigkeit, welche auch nur leicht durch den vorhandenen Dotanden beeinflusst werden kann. Dagegen zeigen dünne Hafniumoxidschichten einen um eine Größenordnung größeren pyroelektrischen Koeffizienten, welcher durch den anwesenden Dotanden und seine Konzentration beeinflusst wird, da dieser verantwortlich für die Ausbildung der polaren, orthorhombischen Phase gemacht wird.:1. Motivation and Introduction 2. Fundamentals 2.1. Dielectrics and their Classification 2.2. Polarization 2.3. Pyroelectricity 2.4. Ferroelectricty 2.5. Phase Transitions 2.6. Applications and Figures of Merit 3. Measurement Methods for the Pyroelectric Coefficient 3.1. General Considerations 3.1.1. Heating Concepts 3.1.2. Thermal Equilibrium 3.1.3. Electric Contact 3.1.4. Separation of Contributions 3.1.5. Thermally Stimulated Currents 3.2. Static Methods 3.2.1. Charge Compensation Method 3.2.2. Hysteresis Measurement Method 3.2.3. Direct Electrocaloric Measurement 3.2.4. Flatband Voltage Shift 3.2.5. X-ray Photoelectron Spectroscopy Method 3.2.6. X-ray Diffraction and Density Functional Theory 3.3. Dynamic Methods 3.3.1. Temperature Ramping Methods 3.3.2. Optical Methods 3.3.3. Periodic Pulse Technique 3.3.4. Laser Intensity Modulation Methods 3.3.5. Harmonic Waveform Techniques 4. Pyroelectric and Ferroelectric Characterization Setup 4.1. Pyroelectric Measurement Setup 4.1.1. Setup and Instrumentation 4.1.2. Automated Sharp-Garn Evaluation of Pyroelectric Coefficients 4.1.3. Further Examples 4.2. Hysteresis Loop Measurements 4.2.1. Instrumentation 4.2.2. Measurement and Evaluation 4.2.3. Examples 5. Investigated Material Systems 5.1. III-Nitride Bulk Semiconductors GaN and AlN 5.1.1. General Structure and Spontaneous Polarization 5.1.2. Applications 5.1.3. Crystal Growth and Doping 5.1.4. Pyroelectricity 5.2. Hafnium Oxide Thin Films 5.2.1. General Structure and Applications 5.2.2. Polar Properties in Thin Films 5.2.3. Doping Effects 5.2.4. Pyro- and Piezoelectricity 6. Results 6.1. The Pyroelectric Coefficient of Free-standing GaN and AlN 6.1.1. Sample Preparation 6.1.2. Pyroelectric Measurements 6.1.3. Lattice Influence 6.1.4. Slope Differences 6.2. Pyroelectricity of Doped Hafnium Oxide 6.2.1. Sharp-Garn Measurement on Thin Films 6.2.2. Effects of Silicon Doping 6.2.3. Dopant Comparison 7. Summary and Outlook A. Pyroelectric Current and Phase under Periodic Thermal Excitation B. Loss Current Correction for Shunt Method C. Conductivity Correction D. Comparison of Pyroelectric Figures of Merit Bibliography Publication List Acknowledgments