Synthesis of Epitaxial MoS 2 /MoO 2 Core-Shell Nanowires by Two-Step Chemical Vapor Deposition with Turbulent Flow and Their Physical Properties.

MoO 2 nanowires (NWs), MoO 2 /MoS 2 core-shell NWs, and MoS 2 nanotubes (NTs) were synthesized by the turbulent flow chemical vapor deposition of MoO 2 using MoO 3 , followed by sulfurization in the sulfur gas flow. The involvement of MoO x suboxide is suggested by density functional theory (DFT) calculations of the surface energies of MoO 2 . The thickness of the MoS 2 layers can be controlled by precise tuning of sulfur vapor flow and temperatures. MoS 2 had an armchair-type winding topology due to the epitaxial relation with the MoO 2 NW surface. A single ∼ few-layer MoO 2 /MoS 2 core-shell structure showed photoluminescence after the treatment with a superacid. The resistivities of an individual MoO 2 NW and a MoS 2 NT were measured, and they showed metallic and semiconducting resistivity-temperature relationships, respectively.