Spectroscopic study of CVD-grown MoO2@MoS2 core–shell nanorods: role of structural geometry

Abstract The chemical vapour deposition of micron-size, horizontal, uniform, high-aspect ratio MoO 2 @MoS 2 core–shell nanorods with a multilayer MoS 2 shell, grown on sapphire and silica substrates, is demonstrated. Alongside, the growth of 2D MoS 2 nanoribbons is also observed, mainly on the silica substrates. The optical and vibrational properties were probed using photoluminescence and Raman spectroscopy. The Raman analysis of the core–shell nanorods is particularly challenging due to overlapping vibrational modes. Further, the resonant Raman condition is simultaneously fulfilled for the MoS 2 shell and the MoO 2 core. A comprehensive vibrational analysis of MoO 2 @MoS 2 core–shell nanorods highlights the unique resonance Raman features that emerge from the interplay between the crystalline MoO 2 core and the multilayer MoS 2 shell. The resonant mode enhancements are found to be selective, unlike the scenario in the materials considered individually. A pronounced blue shift (40–70 meV) in the neutral A-exciton photoluminescence peak is observed, whose plausible origin is discussed. Our findings demonstrate that the structural geometry and interfacial interaction significantly tailor the optical and vibrational properties of MoO 2 @MoS 2 core–shell nanorods.