Fabrication of three-dimensional nanostructures for thermal study

Advance in nanotechnology has made a good understanding of high frequency phonon dominant, nanometer scale thermal transport a necessity. To study nanometer-scale thermal transport in three dimensions, three-dimensional nanostructured materials are needed. In this work, fabrication of sub 100 nanometer periodic dielectric three-dimensional structures and epitaxial nanostructures are discussed. Using self-assembly of colloidal silica particles as a template, various dielectrics of interest were filled to create nanostructured dielectric materials. First, sub-100 nanometer silica nanoparticles were synthesized and used to assemble a colloidal crystal template, opals. Static silicon chemical vapor deposition filled the above templates with amorphous silicon and thermal annealing converted the amorphous silicon to polycrystalline silicon with an average grain size of 10 nanometers. Subsequent etching with dilute ethanolic hydrofluoric acid yielded periodic three-dimensional polycrystalline silicon nanostructures with characteristic skeleton size of around 20 nanometers. Using a similar colloidal crystal template made of 400 nanometer sized silica nanoparticles, cuprous oxide film was epitaxially grown into the template using electrodeposition. These three-dimensional, sub-100 nanometer silicon nanostructures and three-dimensional epitaxial cuprous oxide nanostructures are similar to the length scale of the mean free path of the phonons. The nanostructures fabricated in this thesis provide fabrication tools to prepare samples which can be used to investigate the nanoscale phonon transport