Heteroepitaxial growth in aqueous solutions: Rubidium iodide on mica

Abstract

We have performed a series of experiments in which the heteroepitaxial growth of rubidium iodide on mica was carried out by precipitation from aqueous solution. The process was studied using time-lapse optical microscopy, ex situ atomic-force microscopy, and x-ray diffraction. We find that this is an extremely robust epitaxial growth system, in that highly oriented islands are formed over a wide range of temperatures and evaporation rates. From the x-ray measurements we find that the distribution of azimuthal island orientations is in most cases less than $0.3\ifmmode^\circ\else\textdegree\fi{}$ wide, despite the fact that growth rates are generally well over $1\ensuremath{\mu}\mathrm{m}/\mathrm{s}.$ Using ex situ atomic-force microscopy, we show that during early stages of growth the external morphology of the epitaxial islands crosses over from a circular island shape to a triangular one, at an island size of approximately $1 \ensuremath{\mu}\mathrm{m}.$ Overall, the growth of salts on mica provides a rich environment in which to probe nucleation and growth phenomena as functions of temperature, evaporation rate, and epitaxial misfit.