Post-Fabrication Engineering of Metal Nanoparticle Grain Structure and Faceting

Abstract

In this thesis metallic nanoparticles of varying size and material are annealed in different temperatures for varying durations of time in order to observe how each parameter may affect the number of crystal grains in the particles. The knowledge of how different parameters affect the number of grains was then used to make single crystal particles and enhance their faceting using chemical methods. This study indicates an exponential decay in the number of crystal grains per particle as the annealing temperature is increased, with both palladium and gold particles becoming nearly single crystal when the temperature reached 0.7 of the bulk metals melting temperature. The number of crystal grains in a metal particle have also shown a linear relation to the diameter of the fabricated metal disks in the size range 100 nm-270 nm. A linear relation could be observed even when using different annealing methods and for different metals. In an attempt to enhance the faceting of the metal particles using chemical methods, nanolithography-fabricated palladium particles could be shaped into cubes, and copper disks could be grown in to larger Wulff-shaped crystals.