Refine
Document Type
- Doctoral thesis (8)
Has Fulltext
- yes (8)
Is part of the Bibliography
- no (8)
Keywords
- Heteroepitaxie (3)
- Heteroepitaxy (2)
- Silicon (2)
- Aluminiumnitrid (1)
- CMOS (1)
- Ceria (1)
- Ceroxid (1)
- Computersimulation (1)
- Crosstalk (1)
- Defects (1)
Institute
In dieser Arbeit wird die Entwicklung einer neuartigen fasergekoppelten Wellenleiterweiche beschrieben, womit erstmals das Anwendungspotential elektrooptisch induzierter Wellenleiter für komplexe faseroptische Anwendungen aufgezeigt wird. Die entwickelte Wellenleiterweiche kann das Licht einer Glasfaser auf zwei Glasfasern sowohl wechselseitig schalten als auch mit steuerbarem Leistungsverhältnis aufteilen. Hierzu wird das Prinzip elektrooptisch induzierter Wellenleiter genutzt. Bei diesem Prinzip entsteht in einer aus elektrooptischem Material bestehenden Schicht durch die lokale Brechzahländerung infolge eines elektrischen Feldes oberhalb einer Elektrode ein reversibler Wellenleiter. In den mittels Halbleitertechnologien gefertigten Wellenleiterstrukturen dient das flüssigkristalline Nematogen 5CB als elektrooptisches Material. Hierbei besitzt dessen paranematische Phase eine hohe Transmission über einen breiten Wellenlängenbereich, einen ausgeprägten elektrooptischen Kerr-Effekt und eine Relaxationszeitkonstante kleiner einer Mikrosekunde. Neben dem Kerr-Effekt treten in paranematischen Flüssigkristallen elektrooptische Effekte höherer Ordnung und ein für die Anwendung kritischer feldinduzierter nematisch-paranematischer Phasenübergang auf. In diesem Zusammenhang wird die Eignung paranematischer Flüssigkristalle hinsichtlich der Verwendung in elektrooptisch induzierten Wellenleitern mittels des im Rahmen dieser Arbeit entwickelten Dünnschichtrefraktometers untersucht.
Einleitung: Akustische Oberflächenwellenfilter (SAW Filter) finden in zahlreichen drahtlosen und drahtgebundenen Kommunikationstechnologien sowie in der Sensorik ihren Einsatz. Dabei führt der Trend hin zu immer preiswerteren und kompakteren Lösungen mit noch mehr Funktionalität und noch geringeren Stromverbräuchen. Die Anwendungen erstrecken sich dabei von ultraenergiesparenden Kommunikationssystemen (z. B. für Sensorknoten) bis hin zu preiswerteren Multisensorarrays in der Sensorik (z. B. Biosensoren) sowie auf einem Chip integrierten Mikrofluidik Systemen (z. B. Mikroliterpumpen). Eine Lösung stellt die Integration der SAW Filter auf einem Chip zusammen mit integrierten Schaltkreisen (IC) in der sogenannten komplementären-Metall-Oxid-Halbleiter (CMOS) Technologie dar. Da es sich hierbei um ein neues Forschungsgebiet handelt und nur wenige Forschergruppen auf diesem Gebiet arbeiten sind umfangreiche wissenschaftliche Untersuchungen notwendig, um eine vollständige Integration der SAW Filter zu ermöglichen. Das einzige reinraumkompatible piezoelektrische Material mit einem ausreichend hohen elektromechanischen Kopplungsfaktor (K2) sowie einer hohen akustischen Ausbreitungsgeschwindigkeit (vAlN = 5760 m/s [Bu 2006]) für hohe Arbeitsfrequenzen (bis ~6 GHz) ist dabei Aluminiumnitrid (AlN). Dafür muss es hoch c-achsenorientiert (<2°) aufgewachsen werden. Ein großes Problem bei der Integration ist das elektromagnetische Übersprechen (Crosstalk), welches besonders auf den für die CMOS Technologie notwendigen niederohmigen Siliziumsubstraten auftritt.
Ziel: Diese Doktorarbeit untersucht die Möglichkeit der Integration von AlN basierten SAW Filtern mit Hilfe von diskreten Bauelementen, aufgebaut mit CMOS kompatiblen Schichtsystemen, in Hinblick auf eine spätere CMOS kompatible Vollintegration.
Ergebnisse: Es konnte gezeigt werden, dass AlN basierte Filter mit Hilfe von CMOS kompatiblen Materialien und Prozessschritten hergestellt werden können. Außerdem konnte gezeigt werde, dass AlN sehr gut (full width at half maximum, FWHM: 1,27° - 1,9°) c-achsenorientiert aufgewachsen werden kann. Umfangreiche Simulationen, die mit Hilfe der finiten Element Methode (FEM) durchgeführt wurden, zeigten akustische Wellen (Rayleighwelle R0 und an der Oberfläche geführte Volumenwelle R1) mit Geschwindigkeiten von circa 4200 m/s (R0) bzw. 5200 m/s (R1) im technisch relevanten Frequenzbereich (~2,4GHz). Es wurde festgestellt, dass die akustische Reflektivität von Wolfram basierten Fingerelektroden circa ein bis zwei Größenordnungen höher liegt als bei Aluminium basierten Elektroden. Hergestellte SAW Filter zeigten maximale Resonanzfrequenzen von 3,3 GHz bei einer Wellenlänge von 1,68 µm, diese können noch auf bis zu 6,6 GHz bei einer minimalen Wellenlänge von 0,8 µm gesteigert werden. In dieser Arbeit konnte erstmals ein elektromagnetisches Übersprechen (Crosstalk) von unter -65 dB auf standardmäßig niederohmigen Siliziumsubstraten gezeigt werden. Erste optimierte SAW Filteranwendungen zeigten typische Frequenzantworten mit guter Performance.
Novel oxide buffer approach for GaN integration on Si(111) platform through Sc₂O₃/Y₂O₃ bi-layer
(2012)
Motivation: Preparation of GaN virtual substrates on large-scale Si wafers is intensively pursued as a cost-effective approach for high power/high frequency electronics (HEMT's etc.) and optoelectronic applications (LED, LASER). However, the growth of high quality GaN layers on Si is hampered by several difficulties mainly related to a large lattice mismatch (-17%) and a huge difference in the thermal expansion coefficient (56%). As a consequence, GaN epitaxial layers grown on Si substrates show a high number of defects (threading dislocations etc.), which severely deteriorate the overall quality of the GaN films. Additionally, due to the different thermal expansion coefficients of the substrate and the film, µm-thick GaN layers crack during post-growth cooling. To solve these integration problems, different semiconducting (e.g. AlN, GaAs, ZnO, HfN) and insulating (e.g. Al₂O₃, MgO, LiGaO₂) buffer layers, separating the Si substrate from the GaN film, are applied. Goal: In this thesis, a novel buffer approach for the integration of GaN on Si is proposed and investigated. The new approach employs Sc₂O₃/ Y₂O₃ bilayer templates as a step-graded buffer to reduce the lattice mismatch between GaN and the Si(111) substrate. According to the bulk crystal lattices, since the Y₂O₃ has an in-plane lattice misfit of -2% to Si, Sc₂O₃ -7% to Y₂O₃, the lattice misfit between GaN and the substrate can be theoretically reduced by about 50% from -17% (GaN/Si) to -8% (GaN/Sc₂O₃). Experimental: The GaN/Sc₂O₃/ Y₂O₃/Si(111) heterostructures are prepared in a multichamber molecular beam epitaxy system on 4 inch Si(111) wafers. In order to obtain complete information on the structural quality of the oxide buffer as well as the GaN layer, synchrotron- and laboratory-based x-ray diffraction, transmission electron microscopy and photoluminescence measurements are performed. The topography of the films is characterized by scanning electron microscopy and chemical inter-diffusion is investigated by energy-dispersive x-ray spectroscopy. The nucleation processes of the GaN onSc₂O₃ buff er are followed in-situ by reflection high energy electron diffraction and the interface chemistry is analyzed by means of x-ray photoelectron spectroscopy. Results: It is found, that the Sc₂O₃/ Y₂O₃ buffer approach provides a template of high structural quality for GaN overgrowth. The bi-layer buffer plays a lattice match mediator role between GaN and Si and acts as a barrier against impurity diffusion. GaN grown on Sc₂O₃/ Y₂O₃/Si(111) templates is single crystalline with a wurtzite structure and (0001) oriented. Due to the -8% lattice mismatch between GaN and Sc₂O₃, GaN growth proceeds by the nucleation of 3D islands. The size of the islands, coalescence time and the relaxation process depend on the GaN growth conditions and have a strong influence on the topography of closed layers, crystalline quality (defect density) as well as optical properties. The best GaN material parameters are obtained for the layers grown in Ga-rich regime when the Ga/N ratio is slightly higher than unity. The main three defects found in the µm-thick GaN layers are a) threading dislocation, with density in the order of 10^10 cm-2, b) stacking faults, resulting in cubic inclusions in the hexagonal matrix and c) inversion domain boundaries causing Ga-polar regions in the mainly N-polar film. A theoretical GaN/Sc₂O₃ interface model is discussed to explain these experimental findings. Despite the relatively large number of structural defects, photoluminescence shows sharp and strong donor-bound exciton transition and very low intensity yellow emission, which indicate that GaN layers grown on Sc₂O₃/ Y₂O₃/Si(111) are promising for future optoelectronic applications. Outlook: Future growth strategies will focus on interface engineering approach to further reduce the lattice mismatch between GaN(0001) and Sc₂O₃ (111) surfaces, enable growth of unipolar GaN films and trigger the occurrence of an early 2D-like growth mode to avoid cubic GaN inclusions and guarantee low threading dislocation densities.
The complexity of today´s microelectronic circuitry is not only driven by complementary metal oxide semiconductor (CMOS) scaling, but also by integration of high performance modules for various applications (e.g. wireless and broadband communication systems). These mixed signal circuitries are build up by combining digital CMOS technology with analog SiGe:C hetero-bipolar transistors (HBT) known as SiGe:C BiCMOS technology. State-of-the-art SiGe:C BiCMOS technologies achieve up to the 500 GHz. Nevertheless, Si as semiconductor material is approaching more and more its physical limits, whereby novel approaches have to be found to ensure the future development of SiGe:C HBT BiCMOS technology in order to push the maximum frequency further into the Terahertz regime. Based on this task, two novel material science strategies are investigated in this Ph.D. thesis in terms of material growth and defect studies: A.) Solid-phase epitaxy (SPE) for emitter and base resistivity: This technique has been investigated for local engineering of crystallinity in emitter and base layer of already established SiGe:C HBT technology in order to improve the speed performance. By introducing disilane as new gas source with respect to standard used silane, it is possible to reduce the CVD growth temperature for Si, enabling the differential growth of epitaxial-Si (epi-Si) on Si and amorphous Si (a-Si) on the SiO2 and Si3N4 masks. The so produced requirement for SPE treatments is evaluated for two possible areas of application: A1.) Emitter region and A2.) Base region. In both cases, SPE techniques are applied to change the standard polycrystalline-Si (poly-Si) emitter and base link area on the SiO2 and Si3N4 masks to a fully epi-Si area in order to lower emitter and base resistivity, respectively. B.) III-V/SiGe hybrid device: The ternary compound semiconductor In1-xGaxP [x=0–1] is introduced as potential new collector material as part of an III-V/SiGe hybrid HBT device. With InP having a three times higher saturation velocity, and GaP having a two times bigger bandgap than Si, this approach offers the possibility to adjust speed and power performance of HBTs in a flexible way as a function of the In1-xGaxP collector chemical composition x. The material growth and defect studies in this Ph.D. thesis produced insights, which lead to the following results for future device application: A1.) SPE for emitter region: After investigating the temperature, time and doping concentration dependence on lateral SPE length of in-situ annealed As-doped epi-Si/a-Si test structures, it was possible to crystallize up to 500 nm of a-Si on SiO2 and Si3N4 masks to epi-Si with low defect densities by a combination of 575 °C and 1000 °C postannealing. A2.) SPE for base region: After studying the dependence of time, temperature, thickness, SiO2-capping and Ge incorporation on lateral SPE length of in-situ annealed undoped epi-Si/a-Si test structures, it was possible to crystallize up to 450 nm of SiO2-capped undoped a-Si on SiO2 mask to low-defective epi-Si by 570 °C postannealing. Finally, this technique is applied in a SiGe:C base model structure in order to show the possibility to widen the monocrystalline region around the bipolar window, which results in a possibly improved base resistivity. B.) GaP/Si0.8Ge0.2/Si(001) heterostructure: For pseudomorphic GaP/Si0.8Ge0.2/Si(001) heterostructure growth, the critical thickness of GaP on Si and maximum thermal budget for GaP deposition is evaluated. A detailed structure and defect characterization study by XRD, AFM, and TEM is reported on single crystalline 170 nm GaP/20 nm Si0.8Ge0.2/Si(001) heterostructure. Results show that 20 nm Si0.8Ge0.2 on Si(001) can be overgrown by 170 nm GaP without affecting the pseudomorphism of the Si0.8Ge0.2/Si(001) systems. The GaP layer grows however partially relaxed, mainly due to defect nucleation at the GaP/Si0.8Ge0.2 interface during initial island coalescence. The achievement of 2D GaP growth conditions on Si0.8Ge0.2/Si(001) systems is thus a crucial step for achieving fully pseudomorphic heterostructures. Anti-phase domain-free GaP growth is observed for film thicknesses beyond 70 nm. In addition, no detrimental impurity diffusion could be found in the GaP/Si0.8Ge0.2/Si(001) heterostructure. Finally, it is to mention that further investigation and efforts are still needed to push these new approaches to full integration into SiGe:C HBT BiCMOS technology concepts: A.) For SPE application: Electrical studies are needed in frame of full processed devices to evaluate the value and required modifications for process integration. B.) For III-V/SiGe hybrid device: Future work has to focus on improved 2D GaP layer conditions (before introducing InP) in order to prepare truly pseudomorphic GaP/Si0.8Ge0.2/Si(001) heterostructures with low defect densities. For this purpose, selective GaP growth studies in local HBT Si0.8Ge0.2/Si(001) mesa structures are the next step.
On the compliant behaviour of free-standing Si nanostructures on Si(001) for Ge nanoheteroepitaxy
(2012)
Due to its superior optoelectronic properties, Germanium (Ge) is attracting increasing interest to build up future photonic modules within Si chip baseline technology. Despite clear advantages of Ge integration in Si technology (identical diamond crystal structure with Si, complementary metal oxide semiconductor (CMOS) compatibility due to no contamination risks etc.), it faces also some true challenges limiting the optoelectronic performance. Among them, thermal and lattice mismatch result in too high defect levels (which act as non-radiative recombination centres). Parasitic diffusion and formation of SiGe alloys at elevated temperatures is also a common problem. In this respect, selective chemical vapor deposition Ge heteroepitaxy approaches for high quality Ge nanostructure growth with reasonable thermal budget must be developed for local Ge photonic module integration. A promising vision is offered by the compliant substrate effects within nanometer scale Ge/Si heteroepitaxial structures. Here, in contrast to the classical Ge deposition on bulk Si substrates, the thermal and lattice mismatch strain energy accumulated in the Ge epilayer is partially shifted to the free-standing Si nanostructure. This strain partitioning phenomenon is at the very heart of the nanoheteroepitaxy theory (NHE) and, if strain energy levels are correctly balanced, offers the vision to grow defect-free nanostructures of lattice mismatched semiconductors on Si. In case of the Ge/Si heterosystem with a lattice mismatch of 4.2%, the strain partitioning phenomenon is expected to be triggered when free-standing Si nanopillars with the width of 50 nm and below are used. In order to experimentally verify NHE with its compliant substrate effects, a set of free-standing Ge/Si nanostructures with diameter ranging from 150 to 50 nm were fabricated and investigated. The experimental verification of compliant substrate effects is challenging and requires sophisticated characterization techniques. The main limitation corresponds to a simultaneous detection of a) the strain partitioning phenomenon between Ge and Si and b) the absence of defects on the nano-scale. In this respect, synchrotron-based grazing incidence x-ray diffraction was applied to study the epitaxial relationship, defect and strain characteristics with high resolution and sensitivity in a non-destructive way. Raman spectroscopy supported by finite element method calculations were used to investigate the strain distribution within a single Ge/Si nanostructure. Special focus was devoted to transmission electron microscopy to determine the quality of the Ge epilayer. It was found, that although high quality Ge nanoclusters can be achieved by thermal annealing on Si pillars bigger than 50 nm in width, no proof of strain partitioning phenomenon was observed. In clear contradiction to the present NHE theory, no strain partitioning phenomenon was found even for ~50 nm wide Si pillars for which the compliant substrate effects are expected. The absence of the strain partitioning between Ge and Si is caused by the stress field exerted by the SiO2 growth mask on the Si nanopillar. In contrast to such nanostructures monolithically prepared from a Si(001) wafer, first results in this thesis clearly prove the strain partitioning phenomenon within Ge/Si nanostructures on Silicon–on–insulator substrate. Here, the compliant substrate effects were clearly observed for pillar widths even bigger than 50 nm. This experimental work demonstrates, that NHE with its compliant substrate effects, offers an interesting approach for high quality Ge nanostructures on Si, avoiding even the misfit dislocation network with its non-tolerable electrical activity in Ge nanodevices. However, the theory does not yet include important aspects of thin film growth on the nano-scale and must be further developed. It is the aim of this PhD thesis to provide this experimental basis for the Ge/Si heterosystem. Finally, it is noted that here developed growth approach is fully Si CMOS compatible and is not only relevant for Ge integration but also for other lattice mismatched alternative semiconductors (GaAs etc.) to enable higher performance / new functions in future Si microelectronics technologies.
Current memory technologies, such as DRAM, SRAM, and NAND Flash, which are approaching very difficult issues related to the continuous scaling to and beyond the 16 nm generation, has led research over the past two decades to the discovery of several new memory technologies. In recent years, new emerging nonvolatile memories (NVMs), such as phase-change random access memory (PCRAM), ferroelectric random access memory (FRAM), magnetic random access memory (MRAM), and resistive random access memory (RRAM), have been intensively studied. Among these candidates, RRAM is a very promising and worldwide studied candidate for alternative NVM and a high potential successor for Flash in terms of energy consumption (write current in the μA range compared to mA) and simplicity of process integration.
A fully CMOS compatible TiN/Ti/HfO2/TiN RRAM module was successfully integrated with a select transistor (1T1R memory) in IHP’s technology. Nonetheless, reliability and insufficient understanding of the resistive switching mechanism are the two main issues limiting this memory technology development for e.g. wireless sensor network (WSN) applications. The still unclear atomic-scale mechanism of HfO2-based resistive switches and the identification of the material changes within the insulator must be addressed to suggest a knowledge-based improvement of device performance. In this frame, the Ti/HfO2 interface is thoroughly investigated in this Thesis by complementary materials science techniques.
First, the investigation of the as-deposited Ti/HfO2/TiN cells revealed that: (1) the Ti layer scavenges oxygen atoms stronger from amorphous (a-HfO2) than from monoclinic (m-HfO2) HfO2 films; (2) not only oxygen vacancies but also other impurities in the atomic vapor deposited (AVD) a-HfO2 film, such like nitrogen and carbon (probably resulting from the used AVD precursor chemistry) are present in the HfO2 insulator.
Next, the electrical characterization of Ti/AVD a-HfO2/TiN cells (with voltage applied to the Ti top electrode while TiN bottom electrode was grounded) revealed a clockwise bipolar resistive switching behavior after an electroforming process at positive voltage polarity. Besides, the chemical and electronic changes observed by hard X-ray photoelectron spectroscopy (HAXPES), indicate the creation of n-type dopants in the a-HfO2 film during the electroforming process, probably related to the formation of positively charged oxygen vacancies in a-HfO2 by the electrochemically induced Ti/a-HfO2 interface oxidation.
In order to directly compare electrical with electronic and chemical changes of one and the same RRAM cell, an in-operando HAXPES technique was developed. These unique studies have revealed the following characteristics of the Ti/AVD a-HfO2/TiN cells: (1) the as-deposited cells are able to switch at low electrical power; (2) However, this resistive switching is not stable and an electroforming process with a slightly increased power is required to stabilize the switching event; (3) Electrical changes correlated with HAXPES results and literature indicate that (i) the forming/set electrical power defines the oxygen vacancies concentration in the a-HfO2 and thus the stability of the resistive switching properties and (ii) the stable resistive switching can be described by a push-pull model of oxygen vacancies migration under the influence of an electrical field; (4) Besides, carbon segregation at the Ti/a-HfO2 interface – while increasing the electrical power or cycling the device – shows that the defects physics is not limited only to oxygen vacancies; other defects may thus contribute under electrical stress to the resistive switching phenomenon and need to be included in theoretical models to correctly describe the switching characteristics.
Finally, according to the presented HAXPES results, the Ti/AVD a-HfO2/TiN RRAM cells are classified to the valence change mechanism. The resistive switching mechanism is attributed to the creation and rupture of oxygen vacancies-based conducting filaments and the Ti/HfO2 interface oxidation is of central importance for the defect balance of the RRAM cell. Most importantly, a reduction of carbon content in the AVD-deposited HfO2 improved the reliability of these memory cells.
The Lateral-Photovoltage-Scanning-Method (LPS) operates well for Si, Ge and Si_{1–x}–Ge_x for an analysis in defect regions below one part per million, where Secondary Ion Mass Spectroscopy (SIMS) or X-Ray Fluorescence (XRF) signals fall below its detection limit. Although LPS is well established since 1999, it is still poorly investigated. We used a computational simulation finite volume (FVM) approach, solving the van-Roosbroeck equations in three dimensions using a MUltifrontal Massively Parallel sparse direct Solver MUMPS. The signal transport is simulated by solving the Maxwell equations in two dimension for different sample geometries.
It could be shown that a typical LPS-measurement is distorted due to the samples geometry (except cuboid). This distortion can be simulated, understood and recalculated, as discussed for trapezoidal or cylindrical samples. Also using the signal generation simulation of this measurement technique it can be shown, that the measurement signal is convoluted depending on the inherent minority charge carrier life time reducing the local resolution. An investigation of the local resolution were made using a Gaussian function as the convolution function of this method. A comparison of simulations to real measurements was discussed on silicon samples with boron implantation pattern.
In 1955 Tauc already stated that the bulk photovoltaic effect, causative for the LPS measurement set-up, could be used detecting any quantity, which affects the band structure of a semiconductor.As strain is coupled to the conduction and valence band profiles by the deformation potential theory by van-de-Walle, we investigated the possibility to detect strain variations using LPS simulations. For an n-type Si sample with an on-top stressor stripe (silicon-nitride) the strain distribution in Si got calculated by finite elemente simulation (FEM) using solid mechanics module. By directly converting the strain profile to a single conduction and valence band, FVM LPS simulations were performed. It could be shown, that the LPS voltage can be connected to hole traps caused by the conduction and valence band profile. Therefore we can finally conclude, that the LPS measurement set-up is suitable measuring conduction and valence band variations caused by strain.
Motivation: Ceroxid wurde Beachtung in der Mikroelektronik (z.B. als hoch-k Oxid, Pufferschicht in der Heteroepitaxie) und in der Katalyse (z.B. zur selektiven Oxidation und für Dehydrierungsreaktionen) geschenkt, aufgrund seiner strukturellen (ähnliche Kristallstruktur und kleine Gitterfehlanpassung in Bezug auf Silizium) und elektronischen (Variation des Ce4+/Ce3+-Valenzzustandes und Ausbildung von Sauerstoffvakanzen) Eigenschaften. Deshalb wurden einkristalline, epitaktische Ceroxiddünnfilme ausgiebig untersucht. Obwohl das benachbarte Seltenerdoxid, Praseodymoxid, ergänzende Eigenschaften aufweist, wurde es weniger studiert, aufgrund seines komplexen Phasendiagramms. Da beide Oxide ein flexibles strukturelles (Polymorphismus) und elektronisches (Variation des Valenzzunstandes) Verhalten aufweisen, ist es von Interesse, Cer-Praseodym-Mischoxide zu untersuchen, um gezielt Eigenschaften für die jeweilige Anwendung einzustellen und zu verbessern. Ziel: Zwecks dessen ist es das Ziel dieser Doktorarbeit in einem interdisziplinären Ansatz solche einkristallinen und epitaktischen, binären und ternären Ce1-xPrxO2-δ Dünnfilme zu wachsen und zu charakterisieren, um so qualitative Proben für weitere Grundlagenstudien, bezüglich der strukturellen und elektronischen Eigenschaften, zur Verfügung zu stellen, die für künftige Anwendungen in Mikroelektronik und Katalyse von Interesse sind. Experiment: Solche einkristallinen und epitaktischen Ce1-xPrxO2-δ Dünnfilme wurden auf einem Si(111) Substrat mittels Molekularstrahlepitaxie gewachsen. Eine in-situ Kontrolle über die Kristallwachstumsqualität wurde mittels Beugung hochenergetischer Elektronen bei Reflexion erreicht. Eine detaillierte Strukturaufklärung wurde mittels labor- und synchrotronbasierter Röntgenstreuung durchgeführt. Zusätzlich diente Transmissions-elektronenmikroskopie dazu eine hochauflösende Einsicht in die Struktur zu bekommen. Die strukturelle Charakterisierung wurde mit theoretischen ab-initio Berechnungen untermauert. Um die Stöchiometrie und den Valenzzustand in den ternären Mischoxiden zu bestimmen, wurde Röntgenphotoelektronenspektroskopie benutzt. Die mikroskopische Defektstruktur wurde mittels Ramanspektroskopie untersucht. Schlußendlich gab die Temperatur-programmierte Desorption einen ersten Einblick in das katalytische Verhalten. Ergebnisse: Die strukturellen Untersuchungen implizieren ein epitaktisches, zwillingsfreies, ausschließlich typ-B orientiertes CeO2(111) Wachstum auf Si(111) mittels einer ultradünnen hex-Pr2O3(0001) Pufferschicht. Dies wurde durch die kristallographische Weiterführung des Sauerstoffuntergitters und den Erhalt des halbleitenden Verhaltens an der Ceroxid-Praseodymoxid-Grenzfläche möglich. Eine Stabilisierung von Pr4+ Kationen wurde mittels ab-initio Berechnungn vorausgesagt, um den Grenzflächenübergang zu begünstigen. Auf solchen hex-Pr2O3(0001)/Si(111) Trägern wurde auch das Wachstum von ternären Ce1-xPrxO2-δ Mischoxiden ermöglicht. Eine stöchiometrieabhängige Studie implizierte ebenfalls ein Zusammenspiel von strukturellen und elektronischen Eigenschaften. In Abhängigkeit von dem Pr Gehalt stellte sich heraus, dass in der Tat Mischungen mit Pr3+ Eingliederung in die CeO2 Fluoritmatrix und mit Ce3+ Eingliederung in die hex-Pr2O3 Matrix resultierten. Zwischen diesen beiden Grenzfällen wurde gezeigt, dass eine höhere Pr-Konzentration zu einer höheren Tendenz führte, Ce3+ Kationen in einem Bixbyit Gitter zu bilden. Jedoch konnten Fluoriteinschlüsse nicht ausgeschlossen werden. In einer ersten temperaturabhängigen Studie bezüglich des Reduktionsverhaltens wurde mittels des linear steigenden, integralen O2 Desorptionssignals und des kristallographischen Netzebenenunterschiedes der geheizten Ce1-xPrxO2-δ Mischoxide demonstriert, dass die Sauerstoffspeicherungsfähigkeit aufgrund des Pr4+/Pr3+ Redoxsystems über die Pr-Dotierung maßgeschneidert werden kann. Des Weiteren wurde festgestellt, dass der Kohlenwasserstoffoxidationprozess hauptsächlich über das Ce4+/Ce3+ Redoxsystem gesteuert wird, da die Desorptionstemperatur von CO2 sich mit steigendem Ce Gehalt verringert. Ausblick: Epitaktische und einkristalline Ce1-xPrxO2-δ/Si(111) Heterostrukturen sind in den Forschungsbereichen der Katalyse und Mikroelektronik von Interesse für zukünftige Untersuchungen. Sie können als modelkatalytisches System verwendet werden, um einen tieferen Einblick in die Korrelation von kristallographischer und elektronischer Struktur mit den Reaktionsmechanismen zu erhalten, indem die Komplexität des Systems schrittweise unter definierten Reaktionsbedingungen erhöht wird. Des Weiteren können Anwendungen im Bereich der Mikroelektronik evaluiert werden. „Oxygen vacancy engineering“ in Seltenerdoxiden wird bereits intensiv untersucht, um „room temperature ferromagnetism“ Phänomene zu erklären und gegebenfalls in der Spintronik nutzbar zu machen.