Authors: Sara Martí-Sánchez, Marc Botifoll, Eitan Oksenberg, Christian Koch, Carla Borja, Maria Chiara Spadaro, Valerio Di Giulio, Quentin Ramasse, F. Javier García de Abajo, Ernesto Joselevich, Jordi Arbiol
Published: 2022-07-14
DOI: 10.1038/s41467-022-31778-3
Source: Full article
AbstractStrain relaxation mechanisms during epitaxial growth of core-shell nanostructures play a key role in determining their morphologies, crystal structure and properties. To unveil those mechanisms, we perform atomic-scale aberration-corrected scanning transmission electron microscopy studies on planar core-shell ZnSe@ZnTe nanowires on α-Al2O3 substrates. The core morphology affects the shell structure involving plane bending and the formation of low-angle polar boundaries. The origin of this phenomenon and its consequences on the electronic band structure are discussed. We further use monochromated valence electron energy-loss spectroscopy to obtain spatially resolved band-gap maps of the heterostructure with sub-nanometer spatial resolution. A decrease in band-gap energy at highly strained core-shell interfacial regions is found, along with a switch from direct to indirect band-gap. These findings represent an advance in the sub-nanometer-scale understanding of the interplay between structure and electronic properties associated with highly mismatched semiconductor heterostructures, especially with those related to the planar growth of heterostructured nanowire networks.