Die vorliegende Arbeit beschäftigt sich mit der Herstellung und Charakterisierung von verdünnten magnetischen II-VI und III-V Halbleiter-Dünnschichten. Diese Systeme bieten vereinfachte optische kohärente Kontrolle von Spin-basierten Prozessen und eignen sich hervorragend für den Einsatz in zukünftigen opto-magnetischen Anwendungen. ZnO-, ZnXO-, GaN- und GaXN-Proben (X = Mangan, Cobalt) sind mit Hilfe der naßchemischen Sol-Gel Synthese hergestellt worden. Sie werden mit Hilfe der Photolumineszenzspektroskopie untersucht. Die spektrale Position der elektronischen Niveaus in der Nähe der Bandkante dieser Materialien wird bestimmt, um in weiteren Experimenten die freien und gebundenen Exzitonen einzeln abzufragen. Mit der Methode der zeitaufgelösten differentiellen Transmissionsspektroskopie (TRDT) werden die Lebensdauern dieser Ladungsträger bestimmt und mit ultraschnellen Prozessen der optischen Anregung und Relaxation in Verbindung gebracht. Die Methode der zeitaufgelösten Faraday-Rotation-Spektroskopie (TRFR) wird angewandt, um die kohärente Spindynamik des optisch angeregten Teilchenensembles zu beschreiben. Die Kohärenz unterliegt den Störeinflüssen verschiedener Streumechanismen, die in der vorliegenden Arbeit identifiziert und quantitativ beschrieben werden. Bei einigen untersuchten Materialsystemen (ZnCoO, ZnMnO und GaMnN) wird die jeweilige spezifische Elektron-Ion Austauschenergie N0α bestimmt, welche die Kopplungsstärke der elektronischen Spins zu denen der Dotierionen beschreibt.

Die vorliegende Arbeit beschäftigt sich mit der Herstellung und Charakterisierung von verdünnten magnetischen II-VI und III-V Halbleiter-Dünnschichten. Diese Systeme bieten vereinfachte optische kohärente Kontrolle von Spin-basierten Prozessen und eignen sich hervorragend für den Einsatz in zukünftigen opto-magnetischen Anwendungen. ZnO-, ZnXO-, GaN- und GaXN-Proben (X = Mangan, Cobalt) sind mit Hilfe der naßchemischen Sol-Gel Synthese hergestellt worden. Sie werden mit Hilfe der Photolumineszenzspektroskopie untersucht. Die spektrale Position der elektronischen Niveaus in der Nähe der Bandkante dieser Materialien wird bestimmt, um in weiteren Experimenten die freien und gebundenen Exzitonen einzeln abzufragen. Mit der Methode der zeitaufgelösten differentiellen Transmissionsspektroskopie (TRDT) werden die Lebensdauern dieser Ladungsträger bestimmt und mit ultraschnellen Prozessen der optischen Anregung und Relaxation in Verbindung gebracht. Die Methode der zeitaufgelösten Faraday-Rotation-Spektroskopie (TRFR) wird angewandt, um die kohärente Spindynamik des optisch angeregten Teilchenensembles zu beschreiben. Die Kohärenz unterliegt den Störeinflüssen verschiedener Streumechanismen, die in der vorliegenden Arbeit identifiziert und quantitativ beschrieben werden. Bei einigen untersuchten Materialsystemen (ZnCoO, ZnMnO und GaMnN) wird die jeweilige spezifische Elektron-Ion Austauschenergie N0α bestimmt, welche die Kopplungsstärke der elektronischen Spins zu denen der Dotierionen beschreibt.

La synthèse de semiconducteurs ferromagnétiques à température ambiante est désormais un enjeu majeur pour le développement de l'électronique de spin. Dans ce manuscrit sont présentés les résultats de nos travaux sur le système Germanium dopé Manganèse. Nous y discutons tout d'abord les propriétés structurales de couches minces de GeMn élaborées par épitaxie par jets moléculaires, grâce aux techniques de microscopie électronique en transmission, diffraction d'électrons et de rayons X, et spectroscopie EXAFS. Nous nous sommes particulièrement intéressés à la ségrégation du Mn qui conduit à la formation de phases riches en manganèse. Dans les couches élaborées à basse température (~100°C), cette ségrégation se traduit par une décomposition spinodale 2D qui a pour conséquence la formation de nanocolonnes riches en Mn entourées par une matrice de Ge. La croissance à des températures supérieures à 200 °C conduit en revanche à la formation de précipités métalliques de Ge3Mn5. Dans un second temps, nous avons étudié les propriétés magnétiques de ces différentes phases. Nous avons mis en évidence un comportement superparamagnétique des nanocolonnes et pour certaines conditions de croissance, un comportement ferromagnétique à des températures supérieures à 400K. Nous nous sommes finalement penchés sur des systèmes plus complexes alliant les nanocolonnes de GeMn à d'autres matériaux (GaAs, MnO, Ge), pour démontrer certaines fonctionnalités (exchange bias, auto-organisation des colonnes ...) indispensables à la réalisation de dispositifs spintroniques. L'ensemble de ces résultats ouvre la voie vers l'injection de spin dans les semiconducteurs tels que le Si, Ge et GaAs.

The research presented in this thesis started with the idea to study alcohols as modifiers and dopants in differential ion mobility spectrometry (d-IMS) to produce complicated chemical signatures to explore a concept of chemical labels for product security application. D-IMS is a gas phase atmospheric pressure separation and detection technique which distinguishes compounds based on differences in their ions mobility as their travel under a low and high electric field. The hypothesis was that alcohols will form typical d-IMS products such as protonated monomers and proton bound cluster ions. However, the very first experiments revealed unexpected phenomena which included changes in the mobility of ions over a narrow range of concentrations that could not be explained by existing theory. Another observation was the apparent regeneration of reactant ions. It became evident that the observed phenomena had not been described in the open literature and that addressing the research-questions that were being raised would be essential for the determination of alcohols by d-IMS and its use in medical applications for toxicity screening and monitoring of alcohols. The above discovery shifted the research objective towards a fundamental and comprehensive study on the behaviour of alcohols in d-IMS. This thesis describes designed experiments and constructed systems allowing the efficient study of effect of concentration, electric field and temperature on the d-IMS responses of alcohols. The results of those studies demonstate: extensive fragmentation of alcohols, including previously undescribed fragmentation patterns with regeneration of the hydrated proton; new phenomena of adduct ion formation within the d-IMS drift tube, observed in the case of methanol within a narrow range of concentration; and self-modification of the alpha function of alcohols. This knowledge was exploited by developing an non-invasive analytical method for recovery, separation and detection of toxins from human saliva (including alcohols, diols and GHB) using TD-GC-d-IMS (thermal desorption - gas chromatography d-IMS) within a full range of toxicological concentration levels.

The diploma thesis focuses on the analysis of a document management system (DMS) pilot implementation in the environment of a Czech bank. The thesis is divided into three parts; the first part is theoretical and remaining two parts are practical (analytical). The theoretical part is devoted to summarization of basic theoretical knowledge in the field of DMS and in a pilot deployment of information systems. The second part describes the EMC xCP 2.1 platform and evaluates its advantages and disadvantages compared to competing products. The third part describes the technological implementation and deployment of a new DMS pilot solution in a bank. Further it analyzes and describes the follow-up activities and related projects that increase the DMS usability in a real business applications. The diploma thesis concurrently focuses on the business requirements analysis including constrains of a new solution deployment, as well as the DMS technological aspects description and the solution design. The author of this thesis has been working as an analyst in the IT company and has been in a long-term cooperation with the DMS team in the bank. The motivation for choosing this topic is to make a summary and clarification of knowledge gained on projects in the the bank and to take an advantage of it in the future cooperation.

This thesis solves the problem of a life cycle of a document and its management in a larger organization. It describes demands of companies on document management informating systems. It compares various tools for document desciption, analyzes the requirements and offers a project and implementation of the solution itself.

No description available.

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / The Air Force SEEK EAGLE Office (AFSEO) was chartered by the Secretary of the Air Force in December 1987. The mission of the AFSEO is to provide the United States Air Force increased combat capability through central management of the aircraft-stores certification process and provide in-house engineering and operations research capabilities. Additionally, the AFSEO is required to ensure the future viability of the aircraft-stores organic in-house capability with the insertion of evolving technologies. To accomplish this mission, the AFSEO employs all phases of the test process; from Digital Model and Simulation (DMS) to Open Air Range (OAR) flight tests. The AFSEO desires to prepare for the future DoD environment, and minimize the cost of developing its products that require advanced sensors and telemetry capability. For a number of years, a mainstay in the process has been instrumented aircraft. These aircraft were specially instrumented to support the mission of AFSEO. Similarly, stores were instrumented to obtain environmental data such as loads and vibration. With the rising cost of instrumentation and the national DoD trend to reduce the cost of development and maintenance of instrumentation, a new method will need to be found. Several advanced concepts in ground and airborne instrumentation at Eglin AFB are needed to support the mission of the AFSEO. These include a new generation of telemetry devices, sensors, and data acquisition components to provide rapid and cost effective instrumentation of test aircraft, stores, and suspension equipment. The new generation telemetry will provide integrated circuitry with “peel and stick” subminiature telemetry sensors. These telemetry sensors will provide flutter and structural loads data for aircraft-stores combinations. In conjunction with the telemetry sensors, advanced aircraft platform instrumentation will be needed to match precision flight mechanics to the spatial telemetry measurements for stress, strain, and dynamic activity of stores.

L'atmosphère des hautes latitudes sud demeure très peu documentée à l'heure actuelle. Or, la compréhension des systèmes biogéochimiques à ces latitudes est nécessaire tant pour l'interprétation des archives glaciaires que pour évaluer l'importance de ces régions dans le climat actuel et futur, en liaison notamment avec les émissions océaniques de diméthylsulfure (DMS). Des études de distributions en taille de l'aérosol sur la base côtière antarctique de Dumont d'Urville ont permis de mieux cerner les problèmes de fractionnement de l'aérosol marin par rapport à la composition de l'eau de mer. En hiver, un déficit de sulfate par rapport au sodium ou au chlore est observé. La chronologie et l'ampleur de ce phénomène ont pu être précisés, dans le but de quantifier le nss-sulfate hivernal. Un second phénomène de fractionnement du sel de mer, lié à la remobilisation de HCI et traduit par un déficit de chlore par rapport au sodium, se révèle peu marqué sur le site suite à la combinaison de plusieurs paramètres, parmi lesquels l'influence locale d'émissions ornithogéniques alcalines. Depuis fin 1998, des mesures de DMS et de DMSO complètent les prélèvements d'aérosols continus depuis 1991. Après trois années de mesures, il apparaît une très grande variabilité interannuelle des teneurs en DMS liée à une variabilité importante de la source océanique locale en été. Si les niveaux de DMS paraissent fortement dépendants de cette source à une échelle locale, les espèces oxydées (MSA, sulfate) sont plutôt représentatives en été des émissions océaniques à une échelle régionale. En hiver, leurs teneurs sont très faibles (15 à 20 ng/m3 de nss-sulfate, hors perturbation volcanique, dont une moitié serait d'origine biogénique). Enfin, des études de photochimie en été ont confirmé l'importance d'un puits hétérogène du DMSO qui semble avoir une dépendance photochimique et s'inscrit comme étant une voie de production privilégiée de MSA particulaire.

This thesis work aims at a better understanding of magneto-optical properties of dilute nitrides and II-VI diluted magnetic semiconductor quantum structures. The thesis is divided into two parts. The first part gives an introduction of the research fields, together with a brief summary of the scientific results included in the thesis. The second part consists of seven scientific articles that present the main findings of the thesis work. Below is a short summary of the thesis. Dilute nitrides have been of great scientific interest since their development in the early 1990s, because of their unusual fundamental physical properties as well as their potential for device applications. Incorporation of a small amount of N in conventional Ga(In)As or Ga(In)P semiconductors leads to dramatic modifications in both electronic and optical properties of the materials. This makes the dilute nitrides ideally suited for novel optoelectronic devices such as light emitting devices for fiber-optic communications, highly efficient visible light emitting devices, multi-junction solar cells, etc. In addition, diluted nitrides open a window for combining Si-based electronics with III-V compounds-based optoelectronics on Si wafers, promising for novel optoelectronic integrated circuits. Full exploration and optimization of this new material system in device applications requires a detailed understanding of their physical properties. Papers I and II report detailed studies of effects of post-growth rapid thermal annealing (RTA) and growth conditions (i.e. presence of N ions, N2 flow, growth temperature and In alloying) on the formation of grown-in defects in Ga(In)NP. High N2 flow and bombardment of impinging N ions on grown sample surface is found to facilitate formation of defects, such as Ga interstitial (Gai) related defects, revealed by optically detected magnetic resonance (ODMR). These defects act as competing carrier recombination centers, which efficiently decrease photoluminescence (PL) intensity. Incorporation of a small amount of In (e.g. 5.1%) in GaNP seems to play a minor role in the formation of the defects. In GaInNP with 45% of In, on the other hand, the defects were found to be abundant. Effect of RTA on the defects is found to depend on initial configurations of Gai related defects formed during the growth. In Paper III, the first identification of an interfacial defect at a heterojunction between two semiconductors (i.e. GaP/GaNP) is presented. The interface nature of the defect is clearly manifested by the observation of ODMR lines originating from only two out of four equivalent <111> orientations. Based on its resolved hyperfine interaction between an unpaired electronic spin (S=1/2) and a nuclear spin (I=1/2), the defect is concluded to involve a P atom at its core with a defect/impurity partner along a <111> direction. Defect formation is shown to be facilitated by N ion bombardment. In Paper IV, the effects of post-growth hydrogenation on the efficiency of the nonradiative (NR) recombination centers in GaNP are studied. Based on the ODMR results, incorporation of H is found to increase the efficiency of the NR recombination via defects such as Ga interstitials. In Paper V, we report on our results from a systematic study of layered structures containing an InGaNAs/GaAs quantum well, by the optically detected cyclotron resonance (ODCR) technique. By monitoring PL emissions from various layers, the predominant ODCR peak is shown to be related to electrons in GaAs/AlAs superlattices. This demonstrates the role of the SL as an escape route for the carriers confined within the InGaNAs/GaAs single quantum well. The last two papers are within a relatively new field of spintronics which utilizes not only the charge (as in conventional electronics) but also the quantum mechanical property of spin of the electron. Spintronics offers a pathway towards integration of information storage, processing and communications into a single technology. Spintronics also promises advantages over conventional charge-based electronics since spin can be manipulated on a much shorter time scale and at lower cost of energy. Success of semiconductor-based spintronics relies on our ability to inject spin polarized electrons or holes into semiconductors, spin transport with minimum loss and reliable spin detection. In Papers VI and VII, we study the efficiency and mechanism for carrier/exciton and spin injection from a diluted magnetic semiconductor (DMS) ZnMnSe quantum well into nonmagnetic CdSe quantum dots (QD’s) by means of spin-polarized magneto PL combined with tunable laser spectroscopy. By means of a detailed rate equation analysis presented in Paper VI, the injected spin polarization is deduced to be about 32%, decreasing from 100% before the injection. The observed spin loss is shown to occur during the spin injection process. In Paper VII, we present evidence that energy transfer is the dominant mechanism for carrier/exciton injection from the DMS to the QD’s. This is based on the fact that carrier/exciton injection efficiency is independent of the width of the ZnSe tunneling barrier inserted between the DMS and QD’s. In sharp contrast, spin injection efficiency is found to be largely suppressed in the structures with wide barriers, pointing towards increasing spin loss.