Symmetry Break and Seeded 2D Anisotropic Growth in Ternary CuGaS₂ Nanocrystals

Abstract

In the wurtzite phase, asymmetric growths of nanocrystals are typically observed along the polar [001] direction. Polarity driven layerwise alternative depositions of cations and anions on seed dots mostly drive such directional growths. However, while the reaction condition favored the asymmetric growth for 2D seeds, it breaks the symmetry of the basal plane and allowed the growth along one of the three symmetric directions. Considering Cu2S disks as seeds, the diffusion induced asymmetric growth leading to 2D tadpole shaped (2d-tadpole) ternary CuGaS2 nanostructures is reported here. The formation mechanism of these asymmetric unique ternary nanostructures is elaborately discussed with tailoring the growth patterns via tuning the interface or introducing a dopant. The entire formation process is also compared with standard tadpoles obtained from 0D Cu2S particles, and the parameters for obtaining such anomalous architectures were established. The most exciting chemistry tuned here is the exploration of specific reactivity of a dual sulfur source which led to highly monodisperse nanostructures observed self-assembled on microscopic grids. The entire study from the reaction chemistry to structural transformation are correlated and compared in both 2D and 0D seeded asymmetric growths leading along [100] and [001] directions, respectively.