Controlled doping of 2d transition metal dichalcogenide materials

The substitution of different transitional metal atoms in the crystal lattice of two-dimensional (2D) monolayer transition-metal dichalcogenide (TMDC) materials allows for tuning of the band structure and electrical, optical, and catalytic properties of the materials. There are still obstacles in synthesizing doped metal atoms in 2D materials in a controlled and uniform manner, which must be overcome. Janus TMDC materials have recently sparked the interest of a variety of applications because symmetry-breaking generates an electric field due to the electric field perpendicular to the more electronegative surface. There is no literature on the synthesis and characterization of metal-doped 2D Janus TMDC materials. In this thesis, Ta and Nb doped 2D Janus WSeS monolayers were synthesized and their morphology, structural, and optical properties were examined. First, Ta2O5 and Nb2O5 precursors were homogeneously mixed with WO3 at various Ta: W and Nb: W atom concentrations. Secondly, Ta and Nb doped 2D WSe2 monolayers were produced by the chemical vapor deposition method and then top Se layer of materials were removed by plasma and replaced by S atoms by in-situ thermal sulfurisation. Raman and atomic force microscope confirmed the existence of all 2D metal doped Janus materials in monolayer thickness, respectively. Raman and Photoluminescence spectroscopy analysis were also demonstrated that the chemical and optical properties of Ta and Nb doped WSe2 and Janus WSeS can be modified by a controlled doping strategy. As a result, this thesis demonstrates, for the first time in the literature, that a new and successful method for controlled doping of monolayer TMDC materials and the production of new types of Janus materials can be established.