Property Tuning of Two-Dimensional Materials by Stacking Order and applications of homostructural devices*

The optical and electronic structures of two-dimensional (2D) materials often show very strong layer-dependent properties. Such properties allow us to achieve various functionalities using different thickness (layer number), stacking order and heterostructures. The stacking-dependent properties allow us to build optoelectronic devices using the same material and same thickness, but it is a much less explored topic. Detailed understanding of the inter-layer interaction via stacking order will help greatly in tailoring the properties of 2D materials for applications, e.g. in pn junction, transistors, solar cells and LEDs.

In this talk, we use ultra-low wavenumber Raman and PL techniques and electric measurements, as well as simulation to study 2- & 3-layer 2D MoS₂. The Raman and PL spectra also show clear correlation with layer-thickness and stacking sequence. We fabricated homostructured devices using differently stacked 2-layer MoS₂. Photocurrent measurements and ab initio calculations reveal that difference in the electronic structures mainly arises from competition between spin-orbit coupling and interlayer coupling in different structural configurations.