Study on Controlled CVD Growth of Monolayer MoS2 and its Heterostructures for Optoelectronic Applications
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My PhD thesis focuses on the controlled growth of monolayer MoS2 and MoS2 based heterostructure with other 2D material (WS2), TiO2 nanostructures and plasmonic nanoparticles (Ag, Au). These heterostructures are synthesized by various methods including chemical vapour deposition (CVD), RF sputtering and hydrothermal method. We have studied the controlled large area growth of monolayer MoS2 by CVD technique on a variety of different substrates. We have successfully fabricated large area high quality p-n heterojunction between single layer MoS2 (1L- MoS2) and TiO2 nanorods, grown by in-situ CVD technique showing strong enhancement of PL intensity mediated by the charge transfer due to the p-doping effect in 1L-MoS2 . We have also fabricated TiO2 /Au/MoS2 (TiO2 /Ag/MoS2 ) ternary core-shell heterostructure with an array of Au/Ag nanoparticles (NPs) coated on the hydrothermally grown hierarchical TiO2 nanostructures followed by a direct CVD growth of monolayer MoS2 and studied the effect of the plasmonic NPs on the ternary system, thus, causing a giant enhancement in the PL intensity. We studied the tunability of the photoluminescence (PL) of the monolayer MoS 2 (1L-MoS2) by decorating it with WS2 quantum dots (WS2 QD) by solving the four-energy level model involving coupled carrier dynamics based on the coupled rate equations. We have also developed 1L-MoS2/WS2 QD heterojunction photodetector demonstrating ultrafast and broadband high photodetection.
Supervisor: P. K. Giri