HILLOCK INTERACTIONS DURING CALCITE GROWTH OBSERVED USING IN SITU ATOMIC FORCE MICROSCOPY
Gershonowitz, Jeremy Brett
Calcite, the most thermodynamically stable form of CaCO3, is a common biomineral found in marine organisms such as mollusks and sea urchins. The calcite structures found in these organisms often display non-equilibrium morphologies and increased fracture toughness compared to geologic calcite. It has been shown that the rhombohedral morphology of calcite single crystals grown via spiral growth is reflected in the rhombohedral shape of growth hillocks at the atomic scale. The underlying cause of this similarity is poorly understood. To better understand this morphological link, we present here an in-situ Atomic Force Microscopy study of interactions between neighboring hillocks in pure calcite, and in calcite grown in the presence of glycine. We discovered that in pure calcite, neighboring hillocks can interact in exactly three geometries. Each geometry has a characteristic morphology and effect on the growth of the crystal. We show that the addition of glycine alters these characteristics due to changes in the shape of the hillock and the kinetics at the step edge. Lastly, we present observational evidence of hillock overgrowth, a hypothesis of the factors that cause overgrowth, and a discussion of the implications that hillock overgrowth has on the bulk scale morphology of the crystal. The results presented in this thesis narrow the research gap of the phenomenological link between the atomic and bulk scale morphologies of calcite crystals and may inform future studies that aim to narrow this research gap as well.
Materials Science; Crystal Growth; in situ AFM; Solution Growth; Spiral Growth; Calcite
Estroff, Lara A.
Baker, Shefford P.
Materials Science and Engineering
M.S., Materials Science and Engineering
Master of Science
dissertation or thesis