In-plane anisotropy in van der Waals epitaxial MoS₂ on MoO₂(010)

Transition metal dichalcogenide based 2D/2D or 2D/3D van der Waals heterostructures exhibit superior properties for high-performance electronics, tunneling transistors, and catalysts. Here, we report on the fabrication of high quality 2D/3D MoS₂/MoO₂ heterostructures with an atomic clean interface by one-step chemical vapor deposition. Optical microscopy, atomic force microscopy, Raman spectroscopy, scanning electron microscopy, and energy dispersive spectroscopy measurements reveal the high-quality of as-grown samples and the specific epitaxial relationship between MoS₂ and MoO₂: MoS₂[$1¯1¯$20]//MoO₂[001] and MoS₂[$1¯$100]//MoO₂[201]. Photoluminescence and Kelvin probe force microscopy measurements combined with density functional theory calculations confirm the interfacial charge transfer from MoS₂ to the underlying MoO₂. Furthermore, MoO₂ induced in-plane anisotropy in MoS₂ was revealed using angle-resolved polarized Raman and photoluminescence spectroscopy with anisotropic ratios of 1.27 (Raman) and 1.29 (photoluminescence), respectively, which is most possibly attributed to anisotropic interfacial charge interactions. Our findings provide an excellent platform for the investigation on interfacial effects. Moreover, the in-plane anisotropy in MoS₂ induced by MoO₂ has expanded the application of isotropic MoS₂ in the polarization-dependent fields.