Morphology Evolution during the Solution-Phase Synthesis of Nanostructured Material
Timothy Drews
University of Minnesota
Date:
Thursday, Feb. 23, 2006
Time: 4:00 p.m.
Place: Engineering II, Room 3361
ABSTRACT
The size and shape (e.g. morphology) evolution of nanostructured materials have a critical influence on the final product quality. In this talk, I will first discuss a system, the electrodeposition of on-chip copper interconnects, where understanding how the morphology evolves can lead to the minimization of product failure. I will then describe another system, the hydrothermal growth of silicalite-1 zeolite, where understanding how the morphology evolves can lead to the creation of materials with tailored porosity. A common theme in both systems is the significant understanding of the morphology evolution gained through a combined experimental and simulation approach and its relationship with performance.
In the electrodeposition of interconnects, if the surface roughness and shape evolution are not properly controlled, pre-mature pinch-off of the interconnect (or trench) can occur, entrapping electrolyte and potentially leading to product failure. Multiple additives are used in the electrodeposition bath to control the morphology evolution in the trench. A combined experimental and hierarchical simulation approach was developed to understand the morphology evolution, in order to design optimal baths that will work as interconnect widths are continually decreased.
The morphology evolution of zeolites is also critical to understand because it may lead to strategies for isolating or enhancing the concentration of crystal-like nanoparticles. These nanoparticles can eventually be used to create materials with hierarchical porosity and thin films. Precursor nanoparticles that form spontaneously upon hydrolysis of tetraethylorthosilicate (TEOS) in aqueous solutions of tetrapropylammonium hydroxide (TPAOH) evolve to s ilicalite-1, a molecular sieve crystal that serves as a model for the self-assembly of porous inorganic materials in the presence of organic structure directing agents . The aging and coalescence of the nanoparticles is studied here by SAXS and TEM. A kinetic mechanism, based on the idea of the oriented aggregation of the nanoparticles, is proposed that is in agreement with the experimental findings of nanoparticle crystal shape, size, and yield evolution.