Anisotropic Growth of Otavite on Calcite: Implications for Heteroepitaxial Growth Mechanisms

Abstract

Elucidating the molecular-scale mechanisms driving complex growth behaviors during heteroepitaxial growth in aqueous media has remained a challenging endeavor. Toward this goal, in situ atomic force microscopy was employed to image the heteroepitaxial growth of otavite (CdCO3) at the (1014) surface of calcite (CaCO3) single crystals in static aqueous conditions. Heteroepitaxial growth proceeded via spreading of three-dimensional (3D) islands and two-dimensional (2D) atomic layers at low and high initial saturation levels, respectively. Experiments were carried out as a function of applied force and imaging mode thus enabling determination of growth mechanisms unaltered by imaging artifacts. This approach revealed the significant anisotropic nature of heteroepitaxial growth on calcite in both growth modes and its dependence on supersaturation, film thickness, and substrate topography. The 3D islands not only grew preferentially along the [421] direction relative to the [010] direction, resulting in rod-l...