Theses and Dissertations from UMD

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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM

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2010 - 20112

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Subject: search.filters.subject.Anodic Aluminum Oxide

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    EXPLOITING PROCESS SYNERGY BETWEEN ANODIC ALUMINUM OXIDE NANOTEMPLATES AND ATOMIC LAYER DEPOSITION: FROM THIN FILMS TO 3D NANO-ELECTRONIC DEVICES
    (2011) Banerjee, Parag; Rubloff, Gary W; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Self-assembled, 3D nanoporous templates present an opportunity to develop devices which are lithography-free, massively scalable and hence, highly manufacturable. Self-limited deposition processes on the other hand, allow functional thin films to be deposited inside such templates with precision and unprecedented conformality. Taken together, the combination of both processes provides a powerful `toolbox' to enable many modern nano devices. In this work, I will present data in three parts. First, I will demonstrate the capabilities of Atomic Layer Deposition (ALD), a self-limited thin film deposition technique in preparing nanoalloyed Al-doped ZnO (AZO) thin films. These films are visibly transparent and electrically conducting. Structure-property relationships are established that highlight the power of ALD to tailor film compositions at the nanoscale. Next, I will use ALD ZnO films in conjunction with aged, ALD V2O5 films to form pn junctions which show rectification with an Ion/Ioff as high as 598. While, the ZnO is a well known n-type semiconductor, the discovery of p-type conductivity in aged V2O5 is surprising and is found to be due to the protonic (H+) conductivity of intercalated H2O in V2O5. Thus, we demonstrate a mixed electronic-ionic pn junction for the first time. Finally, I combine the material set of the pn junction with self-assembled, anodic aluminum oxide (AAO) 3D nanoporous templates to create 3D nanotubular pn junctions. The pn junctions are built inside pores which are only 90nm wide and up to 2μm deep and show rectification with Ion/Ioff of 16.7. Process development and integrations strategies will be discussed that allow for large scale manufacturing of such devices a real possibility.
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    A MULTISCALE MODEL FOR AN ATOMIC LAYER DEPOSITION PROCESS
    (2010) Dwivedi, Vivek Hari; Adomaitis, Raymond A; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Atomic layer deposition (ALD) is a deposition technique suitable for the con- trolled growth of thin films. During ALD, precursor gasses are supplied to the reactor in an alternating sequence producing individual atomic layers through self- limiting reactions. Thin films are grown conformally with atomic layer control over surfaces with topographical features. A very promising material system for ALD growth is aluminum oxide. Alu- minum oxide is highly desirable for both its physical and electronic characteristics. Aluminum oxide has a very high band gap (~ 9 ev) and a high dielectric constant (k ~ 9). The choice of precursors for aluminum oxide atomic layer deposition vary from aluminum halide, alkyl, and alkoxides for aluminum-containing molecules; for oxygen-containing molecules choices include oxygen, water, hydrogen peroxide and ozone. For this work a multiscale simulation is presented where aluminum oxide is deposited inside anodic aluminum oxide (AAO) pores for the purposes of tuning the pore diameter. Controlling the pore diameter is an import step in the conversion of AAO into nanostructered catalytic membranes (NCM). Shrinking the pore size to a desired radius allows for the control of the residence time for molecules entering the pore and a method for molecular filtration. Furthermore pore diameter control would allow for the optimization of precursor doses making this a green process. Inherently, the ALD of AAO is characterized by a slow and a faster time scale where film growth is on the order of minutes and hours and surface reactions are near instantaneous. Likewise there are two length scales: film thickness and composition on the order of nanometers and pore length on the order of microns. The surface growth is modeled in terms of a lattice Monte Carlo simulation while the diffusion of the precursor gas along the length of the pore is modeled as a Knudsen diffusion based transport model.