Tuning the electronic and optical properties of 1L-MoS2 through controlled thermal treatments

Molybdenum disulfide (MoS₂) has emerged as a promising two-dimensional (2D) semiconductor for developing electronic and optoelectronic devices due to its unique physical properties, including high carrier mobility and excellent mechanical strength. In particular, MoS₂ is characterized by a thickness dependent bandgap which gives rise to direct transitions between its conduction and valence band in the case of monolayers (1L-MoS₂). This MoS₂ feature, combined with its high absorption coefficient, results in intense photoemission. Despite these attractive properties, precisely controlling the physical characteristics of few-layer MoS₂ such as layer thickness, doping level, crystalline quality, and defect density remains a significant challenge. Different synthesis methods, such as chemical vapor deposition (CVD) and mechanical exfoliation, often result in variations in the material's structure and doping. Additionally, external factors like substrate interactions, strain, and environmental conditions can significantly alter its electronic and optical properties. We present how thermal treatments conducted under controlled atmospheres can predictably modify the electronic and optical properties of 1L-MoS₂, affecting its strain and doping. In particular, we explore the roles of temperature, treatment time, and gas pressure. Our findings, supported by micro-Raman characterizations, show that it is possible to tailor the doping according to temperature and exposure time conditions. Simultaneously, photoluminescence spectroscopy measurements revealed an enhancement of the photoluminescence emission band associated with exciton recombination. Understanding how environment condition influence MoS₂'s physical properties is fundamental not only for optimizing these properties but also for scaling up MoS₂ production through specific post-synthesis processes.