Bandgap Engineering Of Mos2 Flakes Via Oxygen Plasma: A Layer Dependent Study

The ability to modify the band structure of a semiconducting material via doping or defect engineering is of significant importance for the development of many novel applications in emerging nanoelectronics. Here, we show that the electronic transport properties of molybdenum disulfide (MoS2) field effect transistors of various layer thicknesses (up to 8 layers) can be tailored via control exposure to oxygen plasma. We demonstrate that all the samples can be turned into complete insulators with increasing plasma exposure time and that the time required to turn the samples to complete insulators depends on the number of layers (L). We also found that the variation of mobility (μ) with plasma time (t) for all samples can be collapsed onto one curve and that μ follows a relation μ/L ≈ exp(-ρt/L) where ρ = μμ, and μ is the time derivative of μ. X-ray photoelectron spectroscopy data show that MoO3 defected regions were created by oxygen plasma and that the amount of MoO3 increases with plasma time. Our study suggest that the energetic oxygens from the plasma not only interacts with the surface atoms but also propagate deep inside the layers to create MoO3 defects in the MoS2, the transport properties of which can be described as an effective medium semiconductor with a bandgap higher than MoS2