| Growth of the {lcub}100{rcub} face of Archerite (KH2PO4, KDP) was investigated with atomic force microscopy (AFM). Archerite was chosen as a model system for all crystal growth from solutions due its ease of crystallization and long history as the subject of crystal growth research. Preliminary investigations of growth morphology and the kinetics of step motion in the absence of adsorbates were performed so that adsorbate-induced changes could be accurately evaluated. In situ measurements of step motion during growth from supersaturated aqueous solutions allows for the derivation of fundamental kinetic values such as the activation energy, kinetic coefficients, and the step-edge free energy. Ex situ measurements of surfaces removed from growth solutions show the progression of step bunching with time and distance from the growth hillock. The addition of soluble salts of labile trivalent metals, such as Al(III), Fe(III), and Cr(III), stops growth at low supersaturations via step pinning. Step motion in the presence of these adsorbate complexes was compared to the predictions of classic models of crystal growth, revealing several anomalous growth behaviors. The interactions of the adsorbate complexes with the step edge induce the formation and motion of a previously undiscovered morphological feature, supersteps. Additionally, although the dependence of step velocity on supersaturation was similar to model predictions, step motion recovered more rapidly than expected due to morphological changes. However, the labile nature of the metals prevented the stoichiometric identification of the step-pinning moiety. To investigate molecular interactions between adsorbates and the step edge, inert coordination complexes with specific molecular properties were added to the growth solution. Electrostatic attractions alone are not responsible for step-pinning, nor does the presence of inner-sphere phosphate groups assure pinning when the remainder of the inner coordination sphere has incompatible hydrogen-bonding with the lattice. A combination of inner-sphere phosphate groups and ligands with compatible hydrogen bonding are necessary to induce pinning. Additional instrumental techniques included ultraviolet-visible spectroscopy (UV-Vis), capillary electrophoresis (CE), laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), and 31P nuclear magnetic resonance spectroscopy (NMR).*; *Please refer to dissertation for diagrams. |
