Controlling Structure of One-Dimensional van der Waals Metal Halide Nanowires via VLS Growth

초록

Semiconductor materials with van der Waals (vdW) layered structures have attracted attention due to their anisotropic optoelectronic properties, which are strongly influenced by their layer-stacking configurations. While controlling the vdW layer stacking enables the modulation of electronic/photonic properties, existing approaches mainly focus on two-dimensional (2D) growth, offering limited control in vertical stacking geometries. In this presentation, we discuss our recent efforts to fabricate one-dimensional (1D) nanostructures with vdW layer stacks using a vapor-liquid-solid (VLS) growth technique, as well as control their growth (or stacking) orientations and the corresponding optoelectronic properties upon heterostructure fabrication. Using PbI2 growth with Pb catalysts as a model system, we demonstrate two possible growth directions where layers exhibit either transverse or parallel stacking relative to the nanowire axis. While initial growth direction can be regulated through homoepitaxy [1], structural modifications such as twin boundary (TB) introduction or direction change can be achieved by precisely doping additives (e.g., PbBr2) [2]. The resulting multi-segment structures display asymmetric band-edge excitonic emission profiles, depending on the crystallographic orientation of each segment. We further utilize these orientation-controlled vdW nanowires to create heterostructures with various vdW semiconductor materials, investigating the correlation between heterointerface geometry and their corresponding optoelectronic properties. Our results highlight the potential of the VLS method for controlling the optoelectronic and photonic properties of 1D vdW layered semiconductors in a wide range of device applications.