For present day global economies energy use is the single most important criteria determining a nation’s wealth and sustainability. The global energy needs are met primarily by fossil fuels which are of finite supply. One means to extend the life span of the fossil fuel reserves has been to improve the efficiency of existing systems including generation, storage, usage etc., as a means of conservation. This dissertation investigates a motor technology that promises to complement existing conservation techniques. Given advances in high voltage power semiconductors, manufacturing techniques and materials research this dissertation evaluates the potential of the switched impedance motor (SIM), a type of electrostatic motor (ESM), as an efficient alternative to induction machines. Starting with a broad look at how force can be created using electrical means, this dissertation reviews the contributions of prior art, details their inhibitors and develops analytic expressions that allow these inhibitors to be overcome. Using these analytic expressions as design tools allows future SIM designers to realize this motor topology’s potential as a highly efficient machine and a global tool for energy conservation.

Electrets are materials capable of storing oriented dipoles or an electric surplus charge for long periods of time. The term "electret" was coined by Oliver Heaviside in analogy to the well-known word "magnet". Initially regarded as a mere scientific curiosity, electrets became increasingly imporant for applications during the second half of the 20th century. The most famous example is the electret condenser microphone, developed in 1962 by Sessler and West. Today, these devices are produced in annual quantities of more than 1 billion, and have become indispensable in modern communications technology. Even though space-charge electrets are widely used in transducer applications, relatively little was known about the microscopic mechanisms of charge storage. It was generally accepted that the surplus charges are stored in some form of physical or chemical traps. However, trap depths of less than 2 eV, obtained via thermally stimulated discharge experiments, conflicted with the observed lifetimes (extrapolations of experimental data yielded more than 100000 years). Using a combination of photostimulated discharge spectroscopy and simultaneous depth-profiling of the space-charge density, the present work shows for the first time that at least part of the space charge in, e.g., polytetrafluoroethylene, polypropylene and polyethylene terephthalate is stored in traps with depths of up to 6 eV, indicating major local structural changes. Based on this information, more efficient charge-storing materials could be developed in the future. The new experimental results could only be obtained after several techniques for characterizing the electrical, electromechanical and electrical properties of electrets had been enhanced with in situ capability. For instance, real-time information on space-charge depth-profiles were obtained by subjecting a polymer film to short laser-induced heat pulses. The high data acquisition speed of this technique also allowed the three-dimensional mapping of polarization and space-charge distributions. A highly active field of research is the development of piezoelectric sensor films from electret polymer foams. These materials store charges on the inner surfaces of the voids after having been subjected to a corona discharge, and exhibit piezoelectric properties far superior to those of traditional ferroelectric polymers. By means of dielectric resonance spectroscopy, polypropylene foams (presently the most widely used ferroelectret) were studied with respect to their thermal and UV stability. Their limited thermal stability renders them unsuitable for applications above 50 °C. Using a solvent-based foaming technique, we found an alternative material based on amorphous Teflon® AF, which exhibits a stable piezoelectric coefficient of 600 pC/N at temperatures up to 120 °C. / Elektrete sind Materialien, welche orientierte elektrische Dipole oder eine elektrische Überschussladung über längere Zeit speichern können. Der Begriff wurde 1885 von Oliver Heaviside in Anlehnung an das Wort "Magnet" eingeführt. Zunächst nur als wissenschaftliche Kuriosität betrachtet, wurden sie seit Mitte des 20. Jahrhunderts in zunehmendem Maße für technische Anwendungen interessant. Als bekanntestes Beispiel sei hier das 1962 von Sessler und West entwickelte Elektret-Kondensator-Mikrofon erwähnt, welches in jährlichen Stückzahlen von mehr als 1 Milliarde hergestellt wird und aus der modernen Kommunikationstechnik nicht mehr wegzudenken ist. Trotz der weit verbreiteten Anwendungen in der Sensorik war bisher nur wenig über die mikroskopischen Mechanismen der Ladungsspeicherung bekannt. Allgemein wird davon ausgegangen, dass die Überschussladungen in physikalischen oder chemischen Haftstellen gespeichert sind. Bisherige Experimente zur thermisch stimulierten Entladung ergaben Bindungsenergien unterhalb von 2 eV, was im Widerspruch zu den beobachteten Lebensdauern (extrapoliert wurden Werte von mehr als 100000 Jahren) steht. Mittels photostimulierter Entladung sowie simultaner Messung des Ladungsprofils konnte nun für eine Reihe wichtiger Elektret-Polymere (darunter das unter dem Handelsnamen Teflon® bekannte Polytetrafluorethylen, Polypropylen und Polyethylenterephthalat) erstmals gezeigt werden, dass zumindest ein Teil der Ladungen in tiefen Haftstellen von bis zu 6 eV gespeichert wird, was auf eine tiefgreifende lokale Strukturänderung hinweist. Ausgehend von dieser Information könnten in Zukunft Materialien mit verbesserter Ladungsspeicherung gezielt entwickelt werden. Die neuen Messungen waren erst möglich, nachdem mehrere Verfahren zur Bestimmung elektrischer, elektromechanischer und mechanischer Eigenschaften von Elektreten für einen In Situ-Einsatz weiterentwickelt wurden. So konnten z. B. durch Anregung von kurzen Wärmepulsen in der Polymerfolie Informationen über das Tiefenprofil der Raumladung in Echtzeit gewonnen werden. Die schnelle Abtastung ermöglichte darüber hinaus die dreidimensionale Kartierung von Polarisationsprofilen und Raumladungen. Ein zur Zeit sehr aktives Forschungsgebiet ist die Entwicklung piezoelektrischer Sensorfolien aus geschäumten Elektret-Polymeren. Nach elektrischer Aufladung in einer Korona-Entladung werden Ladungen an der Innenseite der Gasbläschen gespeichert, wodurch das Material piezoelektrische Eigenschaften erhält, welche deutlich besser sind als die der herkömmlichen ferroelektrischen Polymere. Für die bisher gebräuchlichen Polypropylenschäume wurde neben der Temperaturstabilität mittels dielektrischer Resonanzspektroskopie auch das Verhalten unter UV-Bestrahlung untersucht. Aufgrund ihrer beschränkten thermischen Stabilität sind diese Schäume nicht für Anwendungen oberhalb von 50 °C geeignet. Mittels eines Lösungsmittel-basierten Schäumungsverfahrens wurde ein alternativer Werkstoff auf der Basis von amorphem Teflon® AF entwickelt, welcher einen stabilen piezoelektrischen Koeffizienten von 600 pC/N bei Temperaturen von bis zu 120 °C aufweist.

A sensibilidade eletromecânica dos transdutores de eletretos poliméricos resulta em muitas aplicações na engenharia, que motivaram a produção industrial de um filme não homogêneo e eletricamente carregado, denominado filme eletromecânico ou EMFi (ElectroMechanical Film). Um dispositivo alternativo a este EMFi, produzido em nosso laboratório, foi o resultado de uma bolha de ar homogênea termoformada, unida por dois filmes de teflon FEP. Este dispositivo possui uma estrutura similar ao EMFi, mas permite cavidades homogêneas a serem predefinidas e distribuídas no momento em que o dispositivo é produzido, diferindo das células no EMFi com tamanhos diversos e dispersas no interior do filme industrial. A possibilidade de controlar a geometria das bolhas de ar tornou possível o desenvolvimento de um modelo, empregado como uma ferramenta de projeto. A resposta eletromecânica deste transdutor foi modelada e então apresentada neste trabalho. Este modelo analítico avalia o desempenho destes transdutores com somente uma bolha termoformada, para efeitos de simplificação, baseado em capacitores em série, em função da deformação mecânica e da carga elétrica retida no polímero. São representados dinamicamente com parâmetros elétricos e mecânicos, definidos à medida que operam como sensores ou atuadores, com respeito ao limites impostos pela aplicação especificada. O gráfico da resposta em freqüência mostra a freqüência de ressonância e a largura da faixa para meia-amplitude que determina o coeficiente de amortecimento que não pode ser obtido diretamente do modelo analítico. Este gráfico também permite comparar a freqüência natural obtida graficamente com aquela calculada pelo modelo, tornando mais confiável o modelo desenvolvido para o transdutor. Finalmente, melhorias na instrumentação e em condições mais adequadas para os testes são sugeridas, bem como métodos alternativos para trabalhos futuros. / The electromechanical sensibility of polymeric electrets transducers yields many engineering applications which have motivated industrial production of a non-homogeneous and electrically charged film, the so-called electromechanical film (EMFi). An alternative device for this EMFi that has been produced in our laboratory was a homogeneous thermo-formed air bubbles bonded with two teflon FEP films. This device has a structure similar to the EMFi, but allows the homogeneous voids to be pre-defined and distributed at the moment the device is produced, differing the EMFi voids with diverse sizes and dispersed into the industrial film. The possibility to control the air bubbles geometry makes possible the development of a model to be used as a design tool. The electromechanical response of this transducer has been modeled and is presented in this work. Such analytical model evaluates the transducers performance using just a single thermo-formed bubble for simplification purposes, based on series capacitors, which are function of the mechanical deformation and electrical charge trapped in the polymer. They are represented dynamically, with electrical and mechanical parameters being defined as they work as sensors or actuators, regarding the limits imposed by the specified application. A frequency response plot shows the resonance frequency and the bandwidth for the half amplitude, which determines the damper coefficient that cannot be obtained directly from the analytical model. This plot also allows comparison of the natural frequency obtained graphically with the calculated one using the model, making more reliable the transducer model developed. Finally, instrumentation improvements and more suitable test conditions are suggested, as well as alternative methods for future works.

Os termo eletretos piezelétricos de teflon FEP apresentam-se como elementos que podem competir em preço e funcionalidade com os transdutores atuais. Quando carregados impulsivamente, as folhas de teflon FEP retêm cargas elétricas superficiais por um período longo, superior a 500 anos. Excitados mecanicamente, resultam em um alto nível de sinal elétrico e, excitados eletricamente, retornam a energia em deformação mecânica. O processo de fabricação projetado envolve a produção de um transdutor piezelétrico com uma densidade superficial de carga uniforme, através da formação de vacúolos gasosos formados sobre a superfície do filme polimérico. Os altos índices piezelétricos dos transdutores fabricados são confirmados por um sistema de medição estático, também projetado e desenvolvido neste trabalho, onde o coeficiente piezelétrico é medido de maneira direta. / The thermo-formed electrets of teflon FEP films are shown as elements that can be competitive either in price and functionality matters, as per the transducers being used nowadays. Once charged by an impulse voltage, the teflon FEP sheets keep the superficial electric charges for long periods, up to 500 years. Mechanically excited, they result in a high electric signal and, once electrically excited, return in a mechanical deformation. The projected manufactory process includes the production of a piezoelectric transducers with uniformly charged superficial density, though the formation of gaseous vacuoles over the polymeric film surface. The high piezoelectric levels of the manufactured transducers are confirmed by a static measurement system, also projected and developed in this same work, where the piezoelectric coefficient is measured by a direct way.

Os termo eletretos piezelétricos de teflon FEP apresentam-se como elementos que podem competir em preço e funcionalidade com os transdutores atuais. Quando carregados impulsivamente, as folhas de teflon FEP retêm cargas elétricas superficiais por um período longo, superior a 500 anos. Excitados mecanicamente, resultam em um alto nível de sinal elétrico e, excitados eletricamente, retornam a energia em deformação mecânica. O processo de fabricação projetado envolve a produção de um transdutor piezelétrico com uma densidade superficial de carga uniforme, através da formação de vacúolos gasosos formados sobre a superfície do filme polimérico. Os altos índices piezelétricos dos transdutores fabricados são confirmados por um sistema de medição estático, também projetado e desenvolvido neste trabalho, onde o coeficiente piezelétrico é medido de maneira direta. / The thermo-formed electrets of teflon FEP films are shown as elements that can be competitive either in price and functionality matters, as per the transducers being used nowadays. Once charged by an impulse voltage, the teflon FEP sheets keep the superficial electric charges for long periods, up to 500 years. Mechanically excited, they result in a high electric signal and, once electrically excited, return in a mechanical deformation. The projected manufactory process includes the production of a piezoelectric transducers with uniformly charged superficial density, though the formation of gaseous vacuoles over the polymeric film surface. The high piezoelectric levels of the manufactured transducers are confirmed by a static measurement system, also projected and developed in this same work, where the piezoelectric coefficient is measured by a direct way.

A sensibilidade eletromecânica dos transdutores de eletretos poliméricos resulta em muitas aplicações na engenharia, que motivaram a produção industrial de um filme não homogêneo e eletricamente carregado, denominado filme eletromecânico ou EMFi (ElectroMechanical Film). Um dispositivo alternativo a este EMFi, produzido em nosso laboratório, foi o resultado de uma bolha de ar homogênea termoformada, unida por dois filmes de teflon FEP. Este dispositivo possui uma estrutura similar ao EMFi, mas permite cavidades homogêneas a serem predefinidas e distribuídas no momento em que o dispositivo é produzido, diferindo das células no EMFi com tamanhos diversos e dispersas no interior do filme industrial. A possibilidade de controlar a geometria das bolhas de ar tornou possível o desenvolvimento de um modelo, empregado como uma ferramenta de projeto. A resposta eletromecânica deste transdutor foi modelada e então apresentada neste trabalho. Este modelo analítico avalia o desempenho destes transdutores com somente uma bolha termoformada, para efeitos de simplificação, baseado em capacitores em série, em função da deformação mecânica e da carga elétrica retida no polímero. São representados dinamicamente com parâmetros elétricos e mecânicos, definidos à medida que operam como sensores ou atuadores, com respeito ao limites impostos pela aplicação especificada. O gráfico da resposta em freqüência mostra a freqüência de ressonância e a largura da faixa para meia-amplitude que determina o coeficiente de amortecimento que não pode ser obtido diretamente do modelo analítico. Este gráfico também permite comparar a freqüência natural obtida graficamente com aquela calculada pelo modelo, tornando mais confiável o modelo desenvolvido para o transdutor. Finalmente, melhorias na instrumentação e em condições mais adequadas para os testes são sugeridas, bem como métodos alternativos para trabalhos futuros. / The electromechanical sensibility of polymeric electrets transducers yields many engineering applications which have motivated industrial production of a non-homogeneous and electrically charged film, the so-called electromechanical film (EMFi). An alternative device for this EMFi that has been produced in our laboratory was a homogeneous thermo-formed air bubbles bonded with two teflon FEP films. This device has a structure similar to the EMFi, but allows the homogeneous voids to be pre-defined and distributed at the moment the device is produced, differing the EMFi voids with diverse sizes and dispersed into the industrial film. The possibility to control the air bubbles geometry makes possible the development of a model to be used as a design tool. The electromechanical response of this transducer has been modeled and is presented in this work. Such analytical model evaluates the transducers performance using just a single thermo-formed bubble for simplification purposes, based on series capacitors, which are function of the mechanical deformation and electrical charge trapped in the polymer. They are represented dynamically, with electrical and mechanical parameters being defined as they work as sensors or actuators, regarding the limits imposed by the specified application. A frequency response plot shows the resonance frequency and the bandwidth for the half amplitude, which determines the damper coefficient that cannot be obtained directly from the analytical model. This plot also allows comparison of the natural frequency obtained graphically with the calculated one using the model, making more reliable the transducer model developed. Finally, instrumentation improvements and more suitable test conditions are suggested, as well as alternative methods for future works.

Récupérer l'énergie mécanique ambiante est une alternative prometteuse afin d'assurer l'autonomie énergétique d'appareils nomades. Le développement des générateurs électrostatiques souples reste toutefois à ce jour anecdotique du fait des hautes tensions de polarisation employées, de la nécessité de grandes déformations mécaniques mais aussi de l'utilisation de matériaux peu conventionnels et mal caractérisés. Le but de cette thèse est d'apporter des avancées scientifiques et des solutions aux verrous technologiques précités. Tout d'abord, une caractérisation rigoureuse des propriétés électriques et mécaniques de deux matériaux communément utilisés pour ces applications (acrylate VHB 4910 et silicone Polypower) nous a donné accès aux propriétés physiques dans un fonctionnement réel de ces polymères : influence de la précontrainte, de la nature des électrodes... Ces données ont permis d'élaborer des lois analytiques fiables que nous avons ensuite insérées dans un modèle thermodynamique permettant de définir avec précision les puissances et densités d'énergie récupérables pour ces générateurs. Des pistes d'amélioration des matériaux utilisés dans les applications générateurs peuvent être dégagées de notre modèle. Le second verrou à lever concerne la source haute tension de polarisation nécessaire à ces générateurs électrostatiques. Pour cela, nous avons proposé une solution innovante couplant l'élastomère diélectrique à un électret. Différentes configurations de générateurs hybrides dans des géométries 2D et 3D ont été évaluées. Enfin, nous avons réalisé un prototype qui a délivré une puissance de l'ordre de 35µW sachant qu'une optimisation de ce prototype est réalisable et que des puissances récupérées de plusieurs centaines de µW sont tout à fait réalistes. / Scavenging mechanical ambient energy is a promising solution to ensure the autonomy of wearable transducers. Nevertheless, the development of soft electrostatic generator (DEG) is up to now slow down due to the use of high bias voltage, high strain and innovative mischaracterized materials. The aim of this Ph-D thesis is to propose innovative solutions to these technological barriers. Firstly, a complete characterization of the electrical and mechanical properties of two commonly used dielectric polymer (acrylate VHB 4910 and silicone Polypower) has revealed the true physical properties of these polymers and especially the influence of the pre-stress and the nature of the electrode used. Thanks to these data, reliable analytic laws have been proposed and inserted into our thermodynamic model in order to predict the output power and scavenged energy density for the DEG. Moreover, our model allow us to propose improvements for the materials used in these applications. The second challenge is to propose an alternative to the high bias voltage needed for these soft generators. We have proposed an innovative solution combining an electret and a dielectric elastomer. Various configurations of hybrid generators in 2D or 3D geometry have been modelled and evaluated. Finally, a prototype has been designed allowing scavenging 35µW. With an appropriate optimization of our prototype, hundreds of µW can be scavenged.

Wide bandgap (WBG) devices and power electronic converters (PEC) that enable the dynamic control of energy and high-power density designs inevitably contain defects including sharp edges, triple points, and cavities, which result in local electric field enhancements. The intensified local electric stresses cause either immediate dielectric breakdown or partial discharge (PD) that erodes electrical insulators and accelerates device aging. With the goal of addressing these dielectric challenges emerging in power-dense applications, this dissertation focuses on 1) modeling the dielectric characteristics of supercritical fluids (SCFs), which is a new dielectric medium with high dielectric strength and high cooling capability; and 2) establishing the optimal fabrication conditions of electrets, which is a new dielectric solution that neutralizes locally enhanced electric fields. In this dissertation, the dielectric breakdown characteristics of SCFs are modeled as a function of pressure based on the electron scattering cross section data of clusters that vary in size as a function of temperature and pressure around the critical point. The modeled breakdown electric field is compared with the experimental breakdown measurements of supercritical fluids, which show close agreement. In addition, electrets are fabricated based on the triode-corona charging method and their PD mitigation performance is evaluated through a series of PD experiments. Electrets are fabricated under various charging conditions, including charging voltage, duration, polarity, and temperature with the goal of identifying the optimal condition that leads to effective PD mitigation. The PD mitigation performance of electrets fabricated based on these charging conditions is further assessed by investigating the impact of various power electronics voltage characteristics, including dv/dt, polarity, switching frequency, and duty cycle. Electret based electric field neutralization approach is further utilized in increasing the critical flashover voltage associated with the surface flashover voltage. Moreover, due to the high mechanical strength of epoxy composites at cryogenic temperatures, in this dissertation, epoxy-based electrets are fabricated as a solution to PD in high temperature superconducting cables. The experimental demonstrations conducted with electret in this dissertation is dedicated for the establishing the electret based electric field neutralization approach as a dielectric solution for the dielectric challenges in power electronics driven systems.

Topic of the thesis is the production of unipolar digital circuits by means of mass-printing technologies. For this purpose accumulation-mode and depletion-mode field-effect transistors have been used. To realize depletion-mode field-effect transistors charges are injected and stored in the gate-dielectric. Consequently, the charge transport on the semiconductor-dielectric interface is influenced and the threshold voltage can be controlled. To inject charges into the dielectric different technologies have been used and will be discussed in terms of their process parameters. Finally, fully-printed digital circuits with enhanced performance are introduced. / Gegenstand der vorliegenden Arbeit ist die drucktechnische Herstellung von unipolaren digitalen Schaltungen durch eine Kombination von organischen Feldeekttransistoren vom Anreicherungs- und Verarmungstyp. Zur Realisierung von Transistoren vom Verarmungstyp werden Überschussladung in den Gate- Isolator eingebracht und gespeichert, wodurch der Ladungstransport im Transistorkanal insbesondere die Schwellspannung beeinflusst wird. Es werden verschiedene Aufladungstechnologien und deren Prozessparameter diskutiert. Abschließend werden vollständig mit Massendruckverfahren prozessierte, digitale Schaltungen mit verbesserter Signalübertragungscharakteristik vorgestellt.

In view of the importance of charge storage in polymer electrets for electromechanical transducer applications, the aim of this work is to contribute to the understanding of the charge-retention mechanisms. Furthermore, we will try to explain how the long-term storage of charge carriers in polymeric electrets works and to identify the probable trap sites. Charge trapping and de-trapping processes were investigated in order to obtain evidence of the trap sites in polymeric electrets. The charge de-trapping behavior of two particular polymer electrets was studied by means of thermal and optical techniques. In order to obtain evidence of trapping or de-trapping, charge and dipole profiles in the thickness direction were also monitored. <br><br> In this work, the study was performed on polyethylene terephthalate (PETP) and on cyclic-olefin copolymers (COCs). PETP is a photo-electret and contains a net dipole moment that is located in the carbonyl group (C = O). The electret behavior of PETP arises from both the dipole orientation and the charge storage. In contrast to PETP, COCs are not photo-electrets and do not exhibit a net dipole moment. The electret behavior of COCs arises from the storage of charges only. <br><br> COC samples were doped with dyes in order to probe their internal electric field. COCs show shallow charge traps at 0.6 and 0.11 eV, characteristic for thermally activated processes. In addition, deep charge traps are present at 4 eV, characteristic for optically stimulated processes. <br><br> PETP films exhibit a photo-current transient with a maximum that depends on the temperature with an activation energy of 0.106 eV. The pair thermalization length (rc) calculated from this activation energy for the photo-carrier generation in PETP was estimated to be approx. 4.5 nm. The generated photo-charge carriers can recombine, interact with the trapped charge, escape through the electrodes or occupy an empty trap. <br><br> PETP possesses a small quasi-static pyroelectric coefficient (QPC): ~0.6 nC/(m²K) for unpoled samples, ~60 nC/(m²K) for poled samples and ~60 nC/(m²K) for unpoled samples under an electric bias (E ~10 V/µm). When stored charges generate an internal electric field of approx. 10 V/µm, they are able to induce a QPC comparable to that of the oriented dipoles. Moreover, we observe charge-dipole interaction. Since the raw data of the QPC-experiments on PETP samples is noisy, a numerical Fourier-filtering procedure was applied. Simulations show that the data analysis is reliable when the noise level is up to 3 times larger than the calculated pyroelectric current for the QPC. <br><br> PETP films revealed shallow traps at approx. 0.36 eV during thermally-stimulated current measurements. These energy traps are associated with molecular dipole relaxations (C = O). On the other hand, photo-activated measurements yield deep charge traps at 4.1 and 5.2 eV. The observed wavelengths belong to the transitions in PETP that are analogous to the π - π* benzene transitions. The observed charge de-trapping selectivity in the photocharge decay indicates that the charge detrapping is from a direct photon-charge interaction. Additionally, the charge de-trapping can be facilitated by photo-exciton generation and the interaction of the photo-excitons with trapped charge carriers. These results indicate that the benzene rings (C6H4) and the dipolar groups (C = O) can stabilize and share an extra charge carrier in a chemical resonance. In this way, this charge could be de-trapped in connection with the photo-transitions of the benzene ring and with the dipole relaxations. <br><br> The thermally-activated charge release shows a difference in the trap depth to its optical counterpart. This difference indicates that the trap levels depend on the de-trapping process and on the chemical nature of the trap site. That is, the processes of charge detrapping from shallow traps are related to secondary forces. The processes of charge de-trapping from deep traps are related to primary forces. Furthermore, the presence of deep trap levels causes the stability of the charge for long periods of time. / Angesichts der Bedeutung der Ladungsspeicherung in Polymerelektreten für viele Anwendungen, wie z.B. in elektromechanischen Wandler, ist es das Ziel dieser Arbeit, zum Verständnis der zugrundeliegenden Mechanismen der kurz- und langfristigen Ladungsstabilisierung beizutragen sowie mögliche Haftstellen zu identifizieren. Ladungs- und Entladungsprozesse in Elektreten geben Hinweise auf Ladungshaftstellen. Diese Prozesse wurden mit thermischen und optischen Methoden bei gleichzeitiger Messung von Ladungs- und Polarisationprofilen untersucht. Die experimentellen Untersuchungen der vorliegenden Arbeit wurden an Polyethylenterephthalat (PETP) und an Cyclischen-Olefin Copolymeren (COC) durchgeführt. <br><br> PETP ist ein Photoelektret und weist in der Carbonylgruppe (C = O) ein Dipolmoment auf. Die Elektreteigenschaften ergeben sich sowohl aus der Orientierungspolarisation als auch aus der Ladungsspeicherung. Im Gegensatz zu PETP ist COC kein Photoelektret und zeigt auch keine Orientierungspolarisation. Deshalb folgen die Elektreteigenschaften des COC ausschließlich aus der Ladungsspeicherung. Die COC-Proben wurden mit Farbstoffen dotiert, um das innere elektrische Feld zu untersuchen. Diese Systeme zeigen flache Ladungshaftstellen bei 0,6 und 0,11 eV, die durch thermisch stimulierte Prozesse entladen werden sowie tiefe Haftstellen bei 4 eV, die optisch stimuliert werden können. <br><br> PETP-Filme zeigen einen transienten Photostrom mit einem Maximalwert ( jp), der von der Temperatur mit einer Aktivierungsenergie von 0,106 eV abhängt. Der thermische Paarabstand (rc) kann für die Photoladungsgeneration in PETP auf ca. 4,5 nm abgeschätzt werden. Die Photoladungsträger können rekombinieren, mit den gespeicherten Ladungen interagieren, über die Elektroden entkommen oder eine leere Haftstelle einnehmen. <br><br> PETP zeigt einen kleinen quasi-statischen pyroelektrischen Koeffizienten (QPC) von ca. 0,6 nC/(m²K) für nicht polarisierte Proben, ca. 60 nC/(m²K) für polarisierte Proben und ca. 60 nC/(m²K) für nicht polarisierte Proben mit Vorspannung (E ~10 V/µm). Wenn die gespeicherten Ladungen ein internes elektrisches Feld von ca. 10 V/µm generieren können, sind sie in der Lage, einen QPC herbeizuführen, der vergleichbar mit dem von orientierten Dipolen ist. Es ist außerdem möglich, eine Ladungs-Dipol-Wechselwirkung zu beobachten. Da die QPM-Daten von PETP auf Grund des geringen Signals verrauscht sind, wurde ein numerisches Fourier-Filterverfahren angewandt. Simulationen zeigen, dass eine zuverlässige Datenanalyse noch bei einem Signal möglich ist, dessen Rauschen bis zu 3-mal größer ist als der berechnete pyroelektrische Strom. <br><br> Messungen der thermisch stimulierten Entladung von PETP-Filmen ergaben flache Haftstellen bei ca. 0,36 eV, welche mit der Dipolrelaxation der Carbonylgruppe (C = O) assoziiert sind. Messungen der photostimulierten Entladung ergaben tiefe Haftstellen bei 4,1 und 5,2 eV. Die beobachteten Wellenlängen entsprechen Übergängen in PETP analog den π - π* Übergängen in Benzol. Die beobachtete Selektivität bei der photostimulierten Entladung lässt auf eine direkte Wechselwirkung von Photonen und Ladungen schließen. Einen zusätzlichen Einfluß auf die Entladung hat die Erzeugung von Photo-Exzitonen und deren Wechselwirkung mit den gespeicherten Ladungsträgern. Diese Ergebnisse deuten darauf hin, dass die Phenylringe (C6H4) und die Dipolgruppen (C = O) eine zusätzliche Ladung in einer chemischen Resonanz stabilisieren und miteinander teilen können. Daher kann die gebundene Ladung auch durch einen Photoübergang im Benzolring oder durch eine Dipolrelaxation freigesetzt werden. <br><br> Die mittels thermisch stimulierter Entladung bestimmte Tiefe der Haftstellen unterscheidet sich deutlich von den mittels photostimulierter Entladung gemessenen Werten. Flachere Haftstellen werden bei der thermisch stimulierten Entladung gefunden und können sekundären Kräften zugeordnet werden. Die tieferen Haftstellen sind chemischer Natur und können primären Kräften zugeordnet werden. Letztere sind für die Langzeitstabilität der Ladung in Polymerelektreten verantwortlich.