Strain-Modified Chirality in Selenium-Alloyed Tellurium Nanocrystals

We investigated the effects of selenium alloying on the shape chirality of colloidal trigonal tellurium nanocrystals (NCs) containing up to ∼6 at. % Se. Circular dichroism spectroscopy shows stronger optical activity in alloyed samples, relative to pure Te NCs, indicating enhanced shape chirality. X-ray diffraction analysis revealed a contraction of the c-axis lattice parameter, attributed to smaller Se atoms substituting for Te, resulting in compressive strain. Furthermore, the average microstrain increases with increasing Se content, along with the development of strong axial strain distribution anisotropy, which is consistent with the intrinsic anisotropy of the Te lattice. Analysis of interplanar spacings from scanning transmission electron microscopy images at atomic-column resolution confirms the existence of heterogeneous intraparticle strain distributions. Hence, these results imply that substitutional Se point defects in Te cause anisotropic strain gradients, which enhance the tendency of chiral Te NCs to form more asymmetric shapes. This study demonstrates how strain engineering by alloying can be employed to tune the structural and optical properties of colloidal NCs.