Thesis (M.S. in Environmental Engineering)--Vanderbilt University, May 2006. / Title from title screen. Includes bibliographical references.

Thesis (M.S.)--University of Missouri--Rolla, 2007. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed October 23, 2007) Includes bibliographical references (p. 54-57).

Thesis (D.E.)--Lamar University-Beaumont, 2003. / Includes bibliographical references.

No description available.

The mantle is the largest reservoir of many of the Earth’s volatile species. Detailed isotopic studies of noble gases within the mantle volatiles have demonstrated that they are of a primordial origin, which have been trapped in the mantle since the Earth’s accretion. This original volatile signature has continually evolved over time, due to the production of in situ radiogenic isotopes and through the recycling of surface volatiles back into the mantle (Lupton and Craig, 1975; Holland and Ballentine, 2006). The study of noble gases within magmatic samples has enabled the composition and structure of the mantle to be determined and has distinguished the multiple volatile reservoirs (primordial, crustal, marine etc.) that have contributed to the mantle composition sampled. Together with the halogens (Cl, Br and I) they represent key tracers of volatile transport processes in the Earth. Therefore a combined analytical approach including the halogens and noble gases is not only be able to track the influx of surface volatile into the mantle, but also provide a greater understanding to the fundamental controls of transport, storage and partitioning of volatiles within the mantle. A combined noble gas and halogen study was undertaken on three different geological samples sets to determine how surface volatiles interact with the mantle on a variety of different scales. Firstly continental xenoliths from the Western Antarctic Rift were analysed to establish the role of subduction volatiles in the creation of the rifts volcanic products. The xenoliths have 3He/4He ratios of 7.5RA indicating that the rift is dominated by the rising asthenospheric mantle. However the Br/Cl and I/Cl ratio and heavy noble gases within the xenoliths indicate that marine derived volatiles have been incorporated into the mantle beneath the rift and may have provided and fundamental control on the formation of the rift itself. Secondly the role of surface contamination on mantle samples has been evaluated. A transect along a MOR pillow basalt has been analysed for its halogen concentrations in conjunction with the previously determined noble gases. The outer sections are enriched in Cl relative to Br and I due to the assimilation of a high salinity brine during eruption. In contrast the crystalline interior of the pillow has MORB like Br/Cl and I/Cl ratios but elevated 132Xe/36Ar ratios indicative of the incorporation of pelagic sediments. This small scale analytical approach has shown that submarine pillow basalts are prone to contamination from the surrounding marine environment and provides a method for the identification and quantification of marine contamination. Finally the halogens within olivine phenocrysts from three Emperor Seamounts have been analysed to determine the distribution of the halogens within the lower mantle. The I/Cl ratio of the samples evolves from a MORB-like ratio in the oldest seamount to elevated values similar to sedimentary pore fluids and chondrites in the younger seamounts. This indicates that the Hawaiian mantle plume contains isolated pockets of subducted or primordial material which have been isolated from whole mantle mixing and have therefore retained a halogen signature distinct from the average mantle values.

No description available.

This thesis contains four parts. In the first part, we investigate the post treatment of low-temperature-deposited high dielectric constant (high-k) thin films to enhance their properties. The high-pressure oxygen (O2 and O2+UV light) is employed to improve the properties of low-temperature-deposited metal oxide dielectric films and interfacial layer. In this study, 13nm HfO2 thin films are deposited by sputtering method at room temperature. Then, the oxygen treatments with a high-pressure of 1500 psi at 150 ¢J are performed to replace the conventional high temperature annealing. According to the XPS analyses, integration area of the absorption peaks of O-Hf and O-Hf-Si bonding energies apparently raise and the quantity of oxygen in deposited thin films also increases from XPS measurement. In addition, the leakage current density of standard HfO2 film after O2 and O2+UV light treatments can be improved from 3.12¡Ñ10-6 A/cm2 to 6.27¡Ñ10-7 and 1.3¡Ñ10-8 A/cm2 at |Vg| = 3 V. The leakage current density is significantly suppressed and the current transport mechanism is transformed from trap-assisted tunneling to Schottky-Richardson emission due to the passivation of traps inside HfO2 film and interfacial layer. The proposed treatment is applicable for the future flexible electronics. In the second part of this thesis, we study the memory characteristics of CoSi2 nanocrystals with SiO2 or Al2O3/HfO2 multiple layer tunnel oxide. Due to the property of high-k, it can provide thicker physics thickness than thermal oxide (SiO2) under identical equivalent oxide thickness (EOT) and enhances the reliability without reducing the programming speed. By engineering the different dielectric constant materials and the energy band structure, the performance of nonvolatile memory can be improved. The device that employs HfO2/Al2O3/HfO2 as tunnel oxide exhibits better memory window and carrier injection efficiency than the device employing thermal oxide. Furthermore, the device employs Al2O3/HfO2/Al2O3 as tunnel oxide present the better retention characteristics than the device employs HfO2/Al2O3/HfO2 as tunnel oxide. The corresponding mechanisms were also discussed. For the advanced nonvolatile application, high-k material - hafnium oxide was applied on the resistance switching nonvolatile memory device as resistive switching layer with TiN/Ti/HfO2/TiN structure in the third part of this thesis. By using a thin Ti layer as the reactive buffer layer into the anode side, the proposed device exhibits superior bistable characteristics. Since the Ti can easily absorb oxygen atoms from buried HfO2, the TiN/Ti bi-layer can greatly improve the resistive switching characteristics. The mechanism of the proposed device is dominated by the redox reaction between the Hf and HfOX. In addition, the proposed device has multi-bit storage ability to enhance the storage density. From the temperature-dependent measurements, the low ambient temperatures would cause the formation and rupture of the conduction path with discordant quality and quantity during every switching cycle, which give rise to a wide distribution of the HRS and LRS resistance and instability of resistive switching properties. In the fourth part of this thesis, we investigate the characteristics of an advanced Cu-induced resistance switching non-volatile memory with Pt/Cu/SiON/TiN/SiO2/Si structure. By inserting a Cu ultra thin film between the SiON layer and Pt top electrode, the device exhibits bipolar resistive switching characteristics after a forming process at 13.6 V. However, the forming and resistive switching process can not be observed in the device if the Cu thin film is omitted. Additionally, we employ a two-step forming process to reduce the forming voltage to 7.5 V. During the forming process, the bias-induced Cu could form a filament-like stretched electrode, but the ¡§set¡¨ and ¡§forming¡¨ voltage of the proposed device take place on different polarity. Therefore, we suppose a bipolar switching mechanism, and our device is dominated by the formation and rupture of the oxygen vacancies in a conduction path between the Cu filament and TiN button electrode. The device also demonstrates stable resistance states during 105 cycling bias pulse operations and acceptable retention characteristics after an endurance test at 85¢J. The I-V switching curves are analyzed to realize the carrier transport mechanisms in different bias regions and resistance states. Additionally, the effective thickness of the resistance switching layers (deff) for the samples with different SiON thickness is also extracted from the related mechanism and demonstrated that the deff is independent with the initial SiON thickness. The corresponding mechanisms and the deff verify the bipolar switching is dominated by the formation and rupture of the oxygen vacancies in conduction path between Cu filament and TiN bottom electrode.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

No description available.

No description available.