Thesis (M.T.R.P.)-University of KwaZulu-Natal, Durban, 2008.

Thesis (M.Sc.)--University of Hong Kong, 2007. / Includes bibliographical references.

Thesis (M.S.)--University of Wisconsin--Madison, 1981. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves [90]-93).

Thesis (M.S.)--University of Wisconsin--Madison, 1981. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 115-116).

This thesis investigates how to improve transparent flexible water vapour barriers by understanding how water permeates through them. The barriers consisted of a reactively sputtered aluminium oxide coating on an industrial-grade polypropylene substrate. Some also incorporated a di-acrylate smoothing layer. Key deposition conditions were studied and optimised for permeation and visible-light transparency: sputtering power, thickness & sequential deposition rate. One of the main deposition conditions corresponded to increasing coating nitrogen content in order to induce barrier-water interaction. The final investigation consisted of including acrylate layers in different barrier stacking combinations. It was found that thin, high sputter power coatings formed the best barriers to permeation. This was due to denser packing of the oxide and the inclusion of fewer macro-defects (large defects allowing unhindered permeation) and nano-defects (defects small enough to cause the permeant to interact with the coating). No clear benefit to permeation was found from the inclusion of nitrogen, but refractive index was seen to increase and the oxynitride coatings mechanically failed at a greater force than the oxides. This case illustrated the importance of considering the role of permeation through nano-defects: although a high activation energy was achieved for the nitrogen containing films, possibly suggesting greater interaction between the water vapour and the barrier, the amount of permeation was not reduced as the nitrogen gave rise to increased permeation due to nano-defects, thus changing the processing and chemistry can affect both the macro-defect and nano-defect permeation. Smoothing layers were found to reduce the permeation rate by covering large substrate features, thus allowing rough substrates to be used even for high barriers. Although a coating of acrylate on top of a barrier oxide showed no improvement, a 1-2-1-2 stack of smoothing layer (1) and oxide (2) was found to exhibit a large delay in the onset of permeation.

Seepage barriers have been used extensively to mitigate seepage problems in dams and levees. Although the designs of many of these dams and levees have been based on intact seepage barriers, seepage barriers have been shown to be susceptible to deformation and cracking when high differential hydraulic pressures act across the barrier. Cracking and deformation have also been observed due to thermal expansion and contraction during seepage barrier curing. Under certain conditions, a crack can lead to serious seepage problems, which could potentially lead to the development of a low-resistance seepage pathway. Three scenarios have been identified where there is potential for erosion to occur adjacent to a crack in a barrier: 1) erosion at the interface between a fine-grained soil and a course-grained soil, 2) erosion of overlying soil due to flow along a joint in bedrock, and 3) erosion of the barrier material itself. Previous studies have investigated the first mode of erosion and studies are underway to look into the second mode. The objective of this study is to investigate the third mode of erosion and to identify the conditions under which serious seepage problems can develop. The question considered was whether the combination of highly permeable material adjacent to a crack in a seepage barrier and a large differential head across the barrier combine to develop a velocity within the crack that is erosive to the seepage barrier material. Laboratory tests have been performed on a variety of seepage barrier materials to assess the potential for cracks to develop a preferred seepage path leading to a serious seepage problem. The results of this study will be useful in risk assessment studies of dams and levees with existing seepage barriers as well as in the design of new seepage barriers. Having knowledge of the conditions under which problems may occur will aid in the selection of seepage barrier types for new barriers, placement of instrumentation to monitor new and existing barriers, and mitigation of existing barriers where problems have been identified. The data provided will assist engineers in quantitatively assessing the potential for the propagation of critical seepage problems from cracks in seepage barriers.

This document only includes an excerpt of the corresponding thesis or dissertation. To request a digital scan of the full text, please contact the Ruth Lilly Medical Library's Interlibrary Loan Department (rlmlill@iu.edu).

The current test methods that evaluate the liquid water resistance performance of a water resistive barrier (WRB) have various drawbacks. A Hydrostatic Pressure Test Apparatus (HPTA) provided by SMT Research Ltd. was used to develop a unique test method to detect liquid water penetration through WRBs. The sensor used in HPTA has 42 channels and each channel reads an individual electric resistance. Lower electric resistance indicates more liquid water penetrates the sensor, vice versa. The measurement system of the device was studied and tested. The results showed the measurement system works properly to detect amount change of the liquid water applied to the sensor while there is no proportional relationship between the amount of liquid water and electrical resistance. The change between two adjacent electrical readings was evaluated by a factor called Normalized Difference Vegetation Index (NDMI). The NDMI factor was determined to be a better measurement than the value of electrical resistance. Preliminary tests using HPTA with Membrane D and Membrane F were done and the apparatus was found to have water leaking through the joint. The clamping method of HPTA was then modified to solve the problem and further WRBs were tested using the modified device. Six WRB materials, Membrane A, Membrane B, Membrane C, Membrane D, Membrane E and Membrane F were tested and 83 tests were conducted in total. A colormap method was used to evaluate the water resistance ability of each material. Among all materials, Membrane E had the highest water resistive duration of long and a water resistance score (WRS) of 337.14. Membrane F had a lower duration of short and a WRS of 78.75. Membrane C and Membrane D have water resistance durations between very short and short and their WRS were 36.5 and 82.71. Membrane A and Membrane B had the lowest water resistance duration of very short and their WRS were 15.15 and 23.19. Plots of Log R vs. Time and NDMI vs. Time of the edge sensors and center sensors were plotted in MATLAB. The water movement behaviours in the two groups of sensors varied by materials. / Graduate / 2023-06-22

As the semiconductor industries are moving beyond 22 nm node technology, the currently used stacked Ta/TaN diffusion barrier including a copper seed will be unable to fulfill the requirements for the future technologies. Due to its low resistivity and ability to perform galvanic copper fill without a seed layer, ruthenium (Ru) has emerged as a potential copper diffusion barrier. However, its crystallization and columnar nanostructure have been the main cause of barrier failures even at low processing temperatures (300 oC -350 oC). In this study, we have proposed and evaluated three different strategies to improve the performance of the ultrathin Ru film as a diffusion barrier for copper. The first study focused on shallow surface plasma irradiation/amorphization and nitridation of 5 nm Ru films. Systematic studies of amorphization and nitrogen incorporation versus sample bias were performed. XPS, XRD and RBS were used to determine the physico-chemical, crystallization and barrier efficiency of the plasma modified Ru barrier. The nitrogen plasma surface irradiation of Ru films at substrate bias voltage of -350 V showed an improved barrier performance up to 400 oC annealing temperatures. The barrier barely started failing at 450 oC due mainly to nitrogen instability. The second study involved only amorphization of the Ru thin film without any nitrogen incorporation. A low energy ion beam irradiation/amorphization on Ru thin film was carried out by using 60 KeV carbon ions with different irradiation doses. The irradiation energy was chosen high enough so that the irradiation ions pass through the whole Ru thin film and stop in the SiO2/Si support substrate. The C-ion fluence of 5×1016 atoms/cm2 at 60 KeV made the Ru film near amorphous without changing its composition. XRD and RBS were used to determine the relationship between crystallization and barrier efficiency of the carbon irradiated Ru barrier. The amorphized Ru film showed an improved barrier performance up to 400 oC annealing temperatures similar to the plasma nitrided Ru films. The barrier barely began to fail at 450 oC due mainly to crystallization. The third study focused on a study of Al doping of nitrided Ru thin films and their crystallinity with the aim of obtaining a completely amorphous Ru based barrier and stable nitridation. The addition of 4% Al and 14% of nitrogen in Ru produced a near amorphous film. Nitrogen in the film remained stable until the annealing temperature of 450 oC for 10 min in N2 atmosphere. Crystallization growth of the film was inhibited until 450 oC. At 500 oC, the crystallization of the Ru films barely started, but the degree of its crystallization is minimal. The Ru-Al-N film was demonstrated to be an effective diffusion barrier for copper until the annealing temperature of 450 oC and began to fail at 500 oC. The Al doping was shown to stabilize the nitrogen in the Ru thin film barrier inhibiting its crystallization and leading to improved diffusion barrier performance and a gain in processing temperatures of 150 oC -200 oC over the as prepared pure Ru thin film barriers.

Cat Island, Mississippi, the westernmost barrier island in Mississippi Sound, demarcates the northeastern extent of the St. Bernard subdelta of the Mississippi River. The unusual ?T? shape of Cat Island is likely the result of reworking of the original shore-parallel island by westward longshore currents post-abandonment of the St. Bernard Delta. XRD analyses performed on Vibracore samples collected from nearshore Cat Island showed quartz sands were common regardless of depth or location. Clays predominated in sediments at depth near the southern tip of the island but were minor in more surficial sediments. Lithologically, surficial sediments from the south and west were quite similar, particularly the decrease in illite/smectite (I/S) abundance, which may reflect westerly reworking of in situ sediments. Analyses indicate this reworking is more effective in changing local lithology than sediment provenance.