Broken Valley Degeneracy in Epitaxial MoS2 on Plasma-Engineered AlN

Two-dimensional transition metal dichalcogenides represent a highly attractive platform for the development of valleytronic devices due to their unique spin-valley properties. Herein, a plasma-assisted interfacial engineering is proposed to enhance valley polarization and valley splitting in MoS 2 /AlN heterostructure by modifying the surface configurations of AlN substrates. The experimental results show that after the optimized N 2 -plasma treatment, the AlN surface becomes smoother with a decreased migration barrier, thereby facilitating the growth of high-quality MoS 2 . The valley splitting and degree of valley polarization in the optimal sample reach 7.96 meV (the corresponding Landé g factor is 19.6) and 33.8% at −7 T, which are 16.0- and 1.0-fold higher than those in the untreated MoS 2 /AlN heterostructure, respectively. Theoretical simulations indicate that the enhanced spin-valley properties are predominantly ascribed to the AlN surface magnetism induced by the hybridization of P z and P y orbitals of surface N and O atoms. This work opens a new avenue for manipulating spin-valley properties in 2D materials via interfacial engineering.