Interface-Dependent Energy Transfer in Mixed-Dimensional PbI2/SnS van der Waals Heterostructures via Contact Geometry

초록

Heterostructures composed of van der Waals (vdW) layered semiconductor materials have garnered interest due to their anisotropic optoelectronic properties. Capitalizing on the structural anisotropy of 2D lattices, a novel heterostructure configuration can be formed in which the vdW layer edges face the surface of other layers, providing additional control over charge/energy transfer at the heterojunction compared to conventional vertically-stacked or laterally-connected vdW heterostructure geometries. In this context, the ability to integrate multi-dimensional vdW layered structures with various stacking orientations is of critical importance. Here, we report mixed-dimensional heterostructures based on vdW multilayer semiconductor materials ? 1D lead iodide (PbI2) nanowires and 2D tin sulfide (SnS) flakes ? and demonstrate that exciton energy transfer at the heterointerface is dependent on the contact geometry. Employing vapor?liquid?solid (VLS) growth using Pb catalysts, we obtained two different types of PbI2 nanowires oriented in [001] and [010] directions. Their sidewall facets ({100} and {010} planes, respectively) form distinct contact interfaces with the {001} plane of SnS flakes after dry transfer. Structural characterizations, along with optical analyses including photoluminescence (PL) and cathodoluminescence (CL), revealed that excitonic excitation in PbI2 nanowires can be transferred to SnS through their sidewall edges at the heterointerface. This induces luminescence from SnS, which has an indirect bandgap. The vdW contact geometry-dependent energy transfer leads to a substantial increase in excitonic emission from SnS domains at PbI2{100}/SnS{001} heterointerfaces compared to their PbI2{001}/SnS{001} counterparts, with the cathodoluminescence attenuation length being 1.8 times longer for the former configuration. We further confirm that the transferred energy travels efficiently along SnS domain edges via a guided mode.