Ca-doped strontianite-calcite hybrid micropillar arrays formed via oriented dissolution and heteroepitaxial growth on calcite

Even though heteroepitaxial growth of one-dimensional microstructures or three-dimensional islands has been realized via strategies such as chemical vapor deposition, molecular beam epitaxy, and solution phase, researchers have not succeeded in the formation of one-dimensional hybrid microstructures via the combination of heteroepitaxial growth and oriented dissolution up to now. In this work, well ordered single crystalline calcium-doped strontianite-calcite hybrid micropillar arrays with the long axis along the [001] direction of the two phases were formed on calcite (104) substrates via heteroepitaxial growth of strontianite and oriented dissolution of calcite in aqueous solution for the first time. Energy-dispersive spectroscopy analysis shows that the micropillars are composed of strontianite occluded with about 12 mol % of Ca. During the growth process of strontianite, calcite cores formed in the inner side of the strontianite micropillars at the base stage via the oriented dissolution. The lattices of the strontianite and calcite match very well at the interface of calcite and strontianite. A novel formation mechanism is proposed for the formation of Ca-doped strontianite-calcite hybrid micropillars via the synergetic process of the oriented dissolution of one carbonate mineral and the heteroepitaxial growth of another carbonate mineral in Volmer-Weber growth mode with a small lattice misfit. Ca-doped strontianite micropillar arrays might grow epitaxially on the calcite (001) and (104) planes with small misfits.