Exploring the potential of Janus MoSSe and related Janus alloy monolayers

Janus transition metal dichalcogenide monolayers, characterized by their inherent structural out-of-plane asymmetry, represent a significant advancement in the field of two-dimensional materials. This thesis focuses on the fabrication of Janus MoSSe monolayers, their unique properties and their application potential. Different fabrication routes were explored, with the thermal sulfurization of MoSe2 monolayers emerging as the most reliable method. Raman and photoluminescence spectroscopy revealed characteristic signatures of the structural asymmetry and stoichiometric composition. Key findings include spectroscopic indicators for sample quality, such as defect-related vibrational modes and Fano-resonance induced peak asymmetries, and the potential for stoichiometry controlled band gap tuning. Density functional theory was employed to map the effects of strain and doping on Raman shifts in Janus MoSSe monolayers, providing a reference for experimental studies. These findings showed paths to reducing strain via substrate engineering. Comparisons with non-stoichiometric Janus alloys highlighted the impact of stoichiometry and defect density on the doping level, with ideal Janus MoSSe exhibiting lower intrinsic n-doping. Electronic device studies revealed that field-effect transistors (FETs) based on Janus MoSSe exhibit intrinsic n-doping, stable charge transport, and near-Ohmic contacts, outperforming their Janus alloy counterpart. Notably, Janus alloy FETs demonstrated ambipolar behavior at elevated temperatures, possibly attributable to thermally activated defect states. Optoelectronic characterization demonstrated Janus MoSSe's excellent photoresponse, with fast and consistent carrier dynamics largely unaffected by environmental conditions. The material's broad wavelength response and its photoconductive properties positions it as a versatile candidate for light-sensitive applications. This thesis establishes Janus MoSSe as a versatile 2D material with potential in electronic and optoelectronic applications. By addressing challenges in synthesis and exploring its intrinsic behaviors, this work provides a comprehensive foundation for future research on Janus materials.