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High temperature rare earth compounds: Synthesis, characterization and applications in device fabrication

Joseph Reese Brewer, University of Nebraska - Lincoln

Abstract

As the area of nanotechnology continues to grow, the development of new nanomaterials with interesting physical and electronic properties and improved characterization techniques are several areas of research that will be remain vital for continued improvement of devices and the understanding in nanoscale phenomenon. In this dissertation, the chemical vapor deposition synthesis of rare earth (RE) compounds is described in detail. In general, the procedure involves the vaporization of a REClx (RE = Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho) in the presence of hydride phase precursors such as decaborane and ammonia at high temperatures and low pressures. Unlike traditional single source precursor techniques such as metal-organic chemical vapor deposition, the materials produced are of extremely high chemical purity. The crystallographic orientation of as-synthesized rare earth hexaboride nanostructures and gadolinium nitride thin films was controlled by judicious choice of specific growth substrates and modeled by analyzing x-ray diffraction powder patterns and crystallographic models.^ The vapor-liquid-solid mechanism was used in combination with the chemical vapor deposition process to synthesize single crystalline rare earth hexaboride nanostructures. Unlike previously reported synthetic techniques to generate rare earth hexaborides, my synthesis provided control over the tip diameter of the nanomaterials, was applicable to all available rare earth metals and utilized a chemical scheme that was much less toxic. Furthermore, the synthesis provided the first ever doped rare earth hexaboride nanowires. The as produced materials showed excellent electronic properties and could be applicable to many different types of electronic applications.^ The rare earth hexaboride nanostructures were then implemented into two existing technologies to enhance their characterization capabilities. First, the rare earth hexaboride nanowires were used as a test material for the development of a TEM based local electrode atom probe tomography (LEAP) technique. The TEM based LEAP technique is the first to combine atomic resolution crystallographic imaging with angstrom scale 3D compositional mapping. This technique also provided some of the first quantitative compositional information of the rare earth hexaboride systems and is applicable to a wide range of nanowire materials. Second, due to the rigidity and excellent conductivity of the rare earth hexaborides, nanostructures were grown onto tungsten wires for the development of robust, oxidation resistant nanomanipulator electronic probes for semiconductor device failure analysis.^

Subject Area

Chemistry, Inorganic|Nanoscience

Recommended Citation

Brewer, Joseph Reese, "High temperature rare earth compounds: Synthesis, characterization and applications in device fabrication" (2010). ETD collection for University of Nebraska - Lincoln. AAI3412912.
http://digitalcommons.unl.edu/dissertations/AAI3412912

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