Bragg coherent X-ray diffraction imaging of the Sn tip in VLS-grown Sn-ITO nanostructures

Abstract

The crystallization of the liquid Sn tip following vapor-liquid-solid (VLS) growth of Sn-ITO nanostructures, presents an intriguing problem due to the confinement by the bottom substrate and side ITO wall. We investigated the crystalline structure and morphology of the Sn tips grown by VLS on c-plane sapphire using Bragg coherent diffraction imaging (BCDI) with a nanoscale spatial resolution in three dimensions. BCDI reconstructions of individual Sn tips reveal that each one is a single crystal with a high degree of crystalline order. Each tip maintains an overall spherical morphology-reminiscent of a liquid droplet-truncated at its base and one side. Despite this, distinct crystalline facets are identified on the crystal surface. Furthermore, a defective region was observed near the tip-substrate interface, characterized by high strain and reduced crystalline order.