Atomically Architected Silicon Pyramid Single-Crystalline Structure Supporting Epitaxial Material Growth and Characteristic Magnetism

The control of three-dimensional (3D) geometrical shapes is one of important approaches that contribute the development of new functionalities in material science. We produced 3D Si pyramids with atomically flat and reconstructed {111} facet surfaces supporting atomically resolved material growth in 3D space for the first time. The complex 4-fold clean 7×7 and 2×2-Fe low-energy electron diffraction (LEED) patterns reflecting the pyramidal geometry showed the realization of atomically reconstructed facet surfaces on the 3D patterned Si. Cross-sectional transmission electron microscopy (TEM) revealed the epitaxial heterointerfaces between Fe nanofilm and Si facet surfaces. The LEED and TEM results indicate the applicability of the Si pyramid as a supporting substrate for arbitrarily oriented 3D functional structures. The pyramidal Fe nanofilm displayed magnetic properties depending on the geometric shape, owing to the facet surfaces and the sharp facet edges. The unique anisotropic magnetization behavior of the 3D pyramid shape indicates that the epitaxial growth of an arbitrary geometry by virtue of the atomically ordered substrate surfaces in 3D space can contribute to the modification of the functionality.