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Die Dissertation umfasst zwei Themenblöcke: Zum einen wurden die optisch-spektroskopischen Eigenschaften von fluoreszenten, farbstoffbeladenen Polymer-Mikropartikeln untersucht. Zum anderen wurde die Anwendbarkeit solcher Partikel für die Lumineszenzlebensdauer-Kodierung in der Durchflusszytometrie evaluiert. Die Charakterisierung der farbstoffbeladenen Mikropartikel erfolgte mittels optischer Spektroskopie. Am Beispiel mit Rhodamin 6G beladener Polymethylmethacrylat-Partikel konnte ein besseres Verständnis des Einbaus der Farbstoffmoleküle und der resultierenden Fluoreszenz-Charakteristika gewonnen werden. Es stellte sich heraus, dass die Beladungseffizienz stark vom mittleren Partikeldurchmesser und den Synthesebedingungen abhängt. In Verbindung mit den beobachteten optisch-spektroskopischen Eigenschaften wurde geschlussfolgert, dass sich eine farbstoffreiche Schicht an der Oberfläche der Partikel bildet, die sich wesentlich von den sterisch eingebauten Farbstoffmoleküle im Partikelvolumen unterscheidet. Hohe Farbstoffkonzentrationen in dieser Oberflächenschicht führen vermutlich zu Aggregation. Des Weiteren deuten Veränderungen der Fluoreszenzeigenschaften auf intrapartikuläre Energiewanderung bei zunehmender Farbstoffkonzentration hin. Diese Interpretation der experimentellen Ergebnisse konnte qualitativ durch einen Algorithmus zur Simulation der Energiewanderung bestätigt werden. Die Anwendbarkeit der Lumineszenzlebensdauer als Kodierungsparameter in der Zeitdomäne konnte unter Verwendung eines Durchflusszytometer-Prototypen analysiert werden. Die wohl größte Herausforderung bei der Lebensdauermessung in der Durchflusszytometrie ist die kurze Interaktionszeit zwischen Objekt und Anregungslicht. Synthetische Daten wurden herangezogen, um den Einfluss einzelner Messparameter und -bedingungen unabhängig voneinander abzuschätzen. Es konnte festgestellt werden, dass die Lumineszenzlebensdauer als Kodierungsparameter in der Zeitdomäne prinzipiell zugänglich ist. / This thesis comprises two main topics. First, the optical-spectroscopic properties of fluorescent microbeads loaded with organic dyes were studied. In the second part, the feasibility of time-domain luminescence lifetime encoding in flow cytometry based on such microbeads was assessed. The study of the dye-loaded polymer microbeads was based on optical spectroscopy. Poly(methyl methacrylate) beads loaded with rhodamine 6G were used as an example system to achieve a better understanding of the dye incorporation procedure. The dye loading efficiency turned out to be strongly dependent on the mean diameter of the beads and on the amounts of certain compounds used for the bead synthesis. In correlation with the observed fluorescence characteristics, it was deduced that a layer with high local dye concentration forms around each bead. The properties of this layer substantially differ from those of the sterically incorporated dye molecules in the bead core. The high dye concentration in this layer results in aggregation accompanied by the respective changes of the fluorescence characteristics of the beads. Moreover, the observed changes in fluorescence properties indicated the existence of an intra-particulate energy migration process at increased dye loading concentrations. A simulation of the energy migration process based on a random walk algorithm confirmed the interpretation of the experimental results. For the assessment of luminescence lifetime encoding in time-domain flow cytometry, a prototype setup was used. The main issue of lifetime determination in flow cytometry is represented by the short interaction time of only tens of microseconds of the objects with the excitation light spot. Synthetic data were used to study certain measurement parameters and conditions as well as the data analysis procedure independently of other influences. As a result, luminescence lifetime is generally applicable as an encoding parameter in time-domain flow cytometry.

This thesis presents time difference (TD) circuits that are important for measuring fluorescence lifetime, building LIDAR systems, and optimizing digital systems. The contribution of this thesis is to present a systematic organization of TD circuits and to present novel designs for digital-to-time conversion (DTC) and time-to-digital conversion (TDC). Four basic time difference circuits are presented: TD adder, arbiter, time-difference MUX, and time-difference memory. Specifications, symbols, and multiple circuit implementations are presented for each block. Then the basic blocks are combined to form two compound blocks: DTC and TDC. Novel designs are presented for both blocks along with detailed simulation results. The DTC was fabricated in TSMC’s 0.35um high-voltage process. A printed circuit board was designed to interface the DTC chip to a computer and test instruments. The DTC demonstrated 80ps resolution.

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Long-term hot-carrier induced degradation of MOS devices has become more severe as the device size continues to scale down to submicron range. In our work, a simple yet effective method has been developed to provide the degradation laws with a better predictability. The method can be easily augmented into any of the existing degradation laws without requiring additional algorithm. With more accurate extrapolation method, we present a direct and accurate approach to modeling empirically the 0.18-ìm MOS reliability, which can predict the MOS lifetime as a function of drain voltage and channel length. With the further study on physical mechanism of MOS device degradation, experimental results indicated that the widely used power-law model for lifetime estimation is inaccurate for deep submicron devices. A better lifetime prediction method is proposed for the deep-submicron devices. We also develop a Spice-like reliability model for advanced radio frequency RF MOS devices and implement our reliability model into SpectreRF circuit simulator via Verilog-A HDL (Hardware Description Language). This RF reliability model can be conveniently used to simulate RF circuit performance degradation

In modern turbine engines for propulsion and energy generation, thermal barrier coating (TBCs) protect hot-section blades and vanes, and play a critical role in enhancing reliability, durability and operation efficiency. In this study, thermal cyclic lifetime and microstructural degradation of electron beam physical vapor deposited (EB-PVD) Yttria Stabilized Zirconia (YSZ) with (Ni,Pt)Al bond coat and Hf- and/or Y- modified CMSX-4 superalloy substrates were examined. Thermal cyclic lifetime of TBCs was measured using a furnace thermal cycle test that consisted of 10-minute heat-up, 50-minute dwell at 1135C, and 10-minute forced-air-quench. TBC lifetime was observed to improve from 600 cycles to over 3200 cycles with appropriated Hf- and/or Y alloying of CMSX-4 superalloys. This significant improvement in TBC lifetime is the highest reported lifetime in literature with similar testing parameters. Beneficial role of reactive element (RE) on the durability of TBCS were systematically investigated in this study. Photostimulated luminescence spectroscopy (PL) was employed to non-destructively measure the residual stress within the TGO scale as a function of thermal cycling. Extensive microstructural analysis with emphasis on the YSZ/TGO interface, TGO scale, TGO/bond coat interface was carried out by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and scanning electron microscopy (STEM) as a funcion of thermal cycling including after the spallation failure. Focused ion beam in-situ lift-out (FIB-INLO) technique was employed to prepare site-specific TEM specimens. X-ray diffraction (XRD) and secondary ion mass spectroscopy (SIMS) were also employed for phase identification and interfacial chemical analysis. While undulation of TGO/bond coat interface (e.g., rumpling and ratcheting) was observed to be the main mechanism of degradation for the TBCs on baseline CMSX-4, the same interface remained relatively flat (e.g., suppressed rumpling and ratcheting) for durable TBCs on Hf- and/or Y-modified CMSX-4. The fracture paths changed from the YSZ/TGO interface to the TGO/bond coat interface when rumpling was suppressed. The geometrical incompatibility between the undulated TGO and EB-PVD YSZ lead to the failure at the YSZ/TGO interface for TBCs with baseline CMSX-4. The magnitude of copressive residual stress within the TGO scale measured by PL gradually decreased as a function of thermal cycling for TBCs with baseline CMSX-4 superalloy substrates. This gradual decrease corrsponds well to the undulation of the TGO scale that may lead to relaxation of the compressive residual stress within the TGO scale. For TBCs with Hf- and/or Y-modified CMSX-4 superalloy substrates, the magnitude of compressive residual stress within the TGO scale remained relatively constant throughout the thermal cycling, although PL corresponding to the stress-relief caused by localized cracks at the TGO/bond coat interface and within the TGO scale was observed frequently starting 50% of lifetime. A slightly smaller parabolic growth constant and grain size of the TGO scale was observed for TBCs with Hf- and/or Y- modified CMSX-4. Small monoclinic HfO2 precipitates were observed to decorate grain boundaries and the triple pointes within the alpha-Al2O3 scale for TBCs with Hf- and/or Y-modified CMSX-4 substrates. Segregation of Hf/Hf4+ at the TGO/bond coat interfaces was also observed for TBCs with Hf- and/or Y-modified CMSX-4 superalloys substrates. Adherent and pore-free YSZ/TGO interface was observed for TBCs with Hf- and/or Y-modified CMSX-4, while a significant amount of decohesion at the YSZ/TGO interface was observed for TBCs with baseline CMSX-4. The beta-NiAl(B2) phase in the (Ni,Pt)Al bond coat was observed to partially transform into gama prime-Ni3Al (L12) phase due to depletion of Al in the bond coat during oxidation. More importantly, the remaining beta-NiAl phase transformed into L10 martensitic phase upon cooling even though there was no significant difference in these phase transformations for all TBCs. Results from these microstructural observations are documented to elucidate mechanisms that suppress the rumpling of the TGO/bond coat interface, which is responsible for superior performance of EB-PVD TBCs with (Ni,Pt)Al bond coat and Hf- and/or Y-modified CMXS-4 superalloy.

Lifetime and obsolescence of components for computer-based systems poses issues for continued usage and maintenance of the systems. This thesis investigates possible alternatives for lifetime extension of a train identification system used in Stockholm Metro. Research of other train identification systems available on the market were made to enable a cost comparison between lifetime extension and system replacement. Methods for extending lifetime of computer-based system, where components are obsolete, were investigated. Since most system documentation was inaccessible a reverse- engineering approach was chosen. Through usage of electrical schematics acquired and open-source hardware descriptions a hardware emulator was developed, which is directly compatible with the existing hardware. The total amount of resources used indicates it is possible to extend the systems lifetime at a low cost, as compared to the cost of system replacement. / Livslängd och åldrande av komponenter för datorbaserade system utgör problem för fortsatt användande och underhåll av systemen. Den här avhandlingen undersöker möjliga alternativ för livstidsförlängning av ett tågidentifieringssystem som används i Stockholms tunnelbana. Efterforskningar av andra tågidentifieringssystem tillgängliga på marknaden genomfördes för att möjliggöra en kostnadsjämförelse mellan livstidsförlängning och systemutbyte. Metoder för förlängning av livslängd av datorbaserade system, där komponenter är föråldrade, undersöktes. Då stora delar av systemdokumentationen inte var tillgänglig valdes baklängesutveckling som strategi. Genom användande av förvärvade elscheman och öppen-källkod hårdvarubeskrivningar kunde en hårdvaruemulator utvecklas, vilken är direkt kompatibel med befintlig hårdvara. Den totala resursanvändningen indikerar att det är möjligt att förlänga systemets livslängd till en låg kostnad, jämfört med kostnaden för ett systembyte.

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