Interfacial Effects on the Photoluminescence Properties of Epitaxial Monolayer MoS2 on MoO2 on C-Sapphire

Interfacial interactions, including interfacial charge transfer and strain, play important roles in the applications of 2D layered materials. Recently, MoO 2 have been widely used as precursors or substrates for growth of high-quality MoS 2 . Herein, photoluminescence (PL) and Raman spectroscopy are used to investigate the dependence of epitaxial monolayer MoS 2 PL properties on MoO 2 nanoflakes in different thicknesses on c-sapphire. On all MoO 2 nanoflakes, the trion exciton of MoS 2 disappears due to the interfacial charge transfer from MoS 2 to MoO 2 . The neutral exciton of MoS 2 exhibits a ≈60 meV redshift on thick MoO 2 nanoflakes compared to those either on c-sapphire or on thin MoO 2 nanoflakes, which is attributed to the relaxation of c-sapphire-induced compressive strain in MoO 2 over a critical thickness. Temperature-dependent PL measurements reveal a stronger electron–phonon interaction in MoS 2 on MoO 2 than on c-sapphire. The findings provide an easy way to tune the properties of MoS 2 via tuning the thickness of MoO 2 buffer layer on c-sapphire.