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A validated predictive model of a-Si:H solar cell arrays was developed. The performance of a-Si:H solar cells was modeled by predicting the performance before degradation first, and then modifying it with terms that account for degradation and recovery effects. A unique approach for the determination of the fundamental rate controlling parameters for the degradation and recovery process was carried out by observing the variation of the short-circuit current. The experimental annealing of a-Si:H silicon samples showed that the percent recovery from the degraded state to the as-grown state by annealing was virtually independent of the initial state at the start of the annealing process. This allowed the recovery parameters to be determined independently of the prior degradation process. An extremely simple and fast running algorithm for the long-term performance was developed in terms of the incident solar radiation, the panel temperature, and the total radiation exposed. Also it was found that the entire process of the Staebler-Wronski effect could be adequately represented by a correlation in which the degradation and recovery processes are solely a function of the total radiation exposure of the panel at ambient conditions.

Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Silicon-germanium (SiGe) BiCMOS technology platforms have proven invaluable for implementing a wide variety of digital, RF, and mixed-signal applications in extreme environments such as space, where maintaining high levels of performance in the presence of low temperatures and background radiation is paramount. This work will focus on the investigation of the total-dose radiation tolerance of a third generation complementary SiGe:C BiCMOS technology platform. Tolerance will be quantified under proton and X-ray radiation sources for both the npn and pnp HBT, as well as for an operational amplifier built with these devices. Furthermore, a technique known as junction isolation radiation hardening will be proposed and tested with the goal of improving the SEE sensitivity of the npn in this platform by reducing the charge collected by the subcollector in the event of a direct ion strike. To the author's knowledge, this work presents the first design and measurement results for this form of RHBD.

This thesis evaluates the suitability of silicon-germanium technology for electronic systems intended for extreme environments, such as ambient temperatures outside of military specification (-55 degC to 125 degC) range and intense exposures to ionizing radiation. Silicon-germanium devices and circuits were characterized at cryogenic and high-temperatures (up to 300 degC) and exposed to ionizing radiation, providing empirical evidence that silicon-germanium is an excellent platform for terrestrial and space-based electronic applications.

Microstructure changes in uranium and uranium/metal alloys due to radiation damage are of great interest in nuclear science and engineering. Titanium has attracted attention because of its similarity to Zr. It has been proposed for use in the second generation of fusion reactors due to its resistance to radiation-induced swelling. Aluminum can be regarded as a standard absorbing material or backing material for irradiation targets. Initial study of thin aluminum films irradiation by �������Cf fission fragments and alpha particles from source has been conducted in the Radiation Center, Oregon State University. Initial study of thin aluminum films irradiation by �������Cf fission fragments and alpha particles from source has been conducted in the Radiation Center, Oregon State University. Aluminum can be regarded as a standard absorbing material or backing material for irradiation targets. The AFM investigation of microstructure damages of thin aluminum surfaces revealed that the voids, dislocation loops and dislocation lines, formed in the thin aluminum films after bombardment by �������Cf fission fragments and alpha particles, depends on the irradiation dose. The void swelling and diameter and depth of voids increase linearly with the fluence of particles and dose; however, the areal density of voids decreased when formation of dislocation loops began. Study of deposition of uranium on titanium backing material by molecular plating and characterization of produced U/Ti film has been performed. The U/Ti film has smooth and uniform surfaces but the composition of the deposits is complex and does not include water molecules which probably involve the presence of U (VI). A possible structure for the deposits has been suggested. X-ray diffraction pattern of U/Ti films showed that The U/Ti film has an amorphous structure. Uranium films (0.500 mg/cm��) and stack of titanium foils (thickness 0.904 mg/cm��) were used to study the microstructural damage of the uranium film and its backing material. Irradiation of U/Ti film and Ti foils with 1 MeV/u (136 MeV) �������Xe�������� ions in was performed in the Positive Ion Injector (PII) unit at the Argonne Tandem Linear Accelerator System (ATLAS) Facility at Argonne National Laboratory, IL. Pre- and post- irradiation of samples was analyzed by X-ray diffraction, Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS) and Atomic Force Microscopy (AFM). The irradiation of U/Ti films results in the formation of a crystalline U���O��� phase and polycrystalline Ti phase. Annealing of the thin uranium deposit on a titanium backing at 800��C in the air atmosphere condition for an hour produced a mixture of UO���, U���O���, Ti, TiO and TiO��� (rutile) phases; meanwhile, annealing at 800oC for an hour in the argon environment produced a mixture of ��-U���O���, Ti and TiO��� (rutile) phases. These phenomena indicate that the damage during irradiation was not due to foil heating. Microstructural damage of irradiated uranium film was dominated by void and bubble formation. The microstructure of irradiated titanium foils is characterized by hillocks, voids, polygonal ridge networks, dislocation lines and dislocation networks. Theory predicts that titanium undergoes an allotropic phase transformation at 882.5 ��C, changing from a closed-packed hexagonal crystal structure (��-phase) into a body-centered cubic crystal structure (��- phase). When the titanium foils were irradiated with 136MeV �������Xe�������� at beam intensity of 3 pnA corresponding to 966��C, it was expected that its structure can change from hexagonal-close packed (hcp) to body-centered cubic (bcc). However, in contrast to the theory, transformation from ��-Ti (hcp) phase to fcc-Ti phase was observed. This phenomenon indicates that during irradiation with high energy and elevated temperature, the fcc-Ti phase more stable than the hcp-Ti Phase. / Graduation date: 2012