Revisiting the Twin Plane Re-entrant Edge Growth Mechanism at an Atomic Scale by Electron Microscopy

Abstract

We conducted an extensive electron microscopy study on surface and defect structures of boron suboxide/suboxycarbide platelets by examining them under various imaging conditions, e.g., side-view and top-view perspectives. It was determined that a twin plane re-entrant edge mechanism was responsible for the growth process at an atomic scale. Moreover, this thorough investigation provided an opportunity to resolve several critical issues regarding this otherwise well-known growth mechanism for metallic nanostructures. In this study, the platelets contained multiple {001} twin lamellae parallel to basal planes and their side faces were mainly enclosed by {101} facets. Vertical growth was heterogeneously nucleated of {001}-type growth twins that were confined at the corners. In lateral growth, nucleation sites were greatly extended to twin re-entrant edges around all side faces. No secondary growth twins were introduced during lateral growth because {101}-type side faces were not twin planes. This work clearly establishes that surface structures of twinned platelets determine nucleation behaviors on basal/side faces and thus control the final morphology, which is relevant to the shape control of metal nanoplates.