Doctor of Philosophy (PhD), Ohio University, 2016, Physics and Astronomy (Arts and Sciences)

The aim of this dissertation is to develop a versatile experimental technique for synthesis of nanoparticles (NPs), which can be used to deposit NPs in various patterns for semiconductor device applications. In addition, the dissertation also aims at the synthesis and characterization of semiconductor NPs capable of nano-scale temperature measurement and infrared sensing. The standard inert gas condensation (IGC) process was modified to synthesize and directly deposit homogeneously sized NPs over a large surface area, with desired deposition pattern. The single 2 mm hole, that is used to extract the NP beam, was replaced with either a multiple-hole pattern (consisting of 25 holes, each 0.31 mm in diameter, arranged as a 5x5 array), or a single slit (20 mm long and 0.13 mm wide) with a continuously rotating (8rpm) substrate. The resultant NP deposition was in the form of multiple dots or a 20 mm long line or a 20 mm diameter circular deposition pattern, and covered a larger substrate area of around 144 mm2 to 350 mm2. SEM study demonstrated uniformity in the size of the NPs throughout the deposition area. Thus, with this IGC modifications the NP deposition area was increased from around 1-2 mm2 to about 350 mm2 and it was possible to vary the NP deposition pattern by varying the holes or slit designs. Next, semiconductor NPs of Erbium doped Aluminum Nitride (AlN:Er) and Indium Antimonide (InSb) were synthesized using IGC, and their morphological, structural and optical properties were investigated. For this the NPs were directly deposited on (111) p-type Silicon wafers, TEM grids and glass cover slips. AlN:Er TEM results reveal that for a fixed set of synthesis parameters the NPs were 13.62 ± 3.84 nm in size and had two different shapes. Nearly 84 percent of the NPs were smaller and cluster-type with undefined shape and the remaining 16 percent were comparatively large and spherical in shape. It was found that change in the synthesis parameters resulted in (open full item for complete abstract)

Committee: Martin Kordesch (Advisor) Subjects: Physics

PhD, University of Cincinnati, 2005, Engineering : Materials Science

In this project, phase transformations and precipitation behavior of Al-Cu nanoparticles were first studied. The nanoparticles were synthesized by a Plasma Ablation process and found to contain a 2∼5 nm thick adherent aluminum oxide scale, which prevented further oxidation. On aging, a precipitation sequence consisting of, nearly pure Cu precipitates to the metastable θ′ to equilibrium θ was observed. The structure of θ′ and its interface with the Al matrix has been characterized. Ultrafine Al-Cu nanoparticles (5∼25 nm) were also synthesized by inert gas condensation and their aging behavior was studied. These particles were found to be quite stable against precipitation. Secondly, pure Al nanoparticles were prepared by the Exploding Wire process and their sintering and consolidation behavior were studied. It was found that Al nanopowders could be processed to bulk structures with high hardness and density. Sintering temperature was found to have a dominant effect on density, hardness and microstructure. Sintering at temperatures >600 degree C led to breakup of the oxide scale, leading to an interesting nanocomposite composed of 100∼200 nm Al oxide dispersed in a bimodal nanometer-micrometer size Al matrix grains. And the randomly dispersed oxide fragments were quite effective in pinning the Al grain boundaries, preventing excessive grain growth and retaining high hardness. Cold rolling and hot rolling were effective methods for attaining full densification and high hardness. Thirdly, the microstructure evolution and mechanical behavior of Al-Al2O3 nanocomposites were studied. The composites can retain high strength at elevated temperature and thermal soaking has practically no detrimental effect on strength. Although the ductility of the composite remains quite low, there was substantial evidence for high localized plasticity. The strengthening mechanisms of the composite include: Orowan strengthening, grain size strengthening and forest strengthening. Finally, (open full item for complete abstract)

Committee: Dr. Vijay Vasudevan (Advisor) Subjects: Engineering, Materials Science