Tuning the electronic structure of monolayer MoS2 towards metal like via vanadium doping

Doping of two-dimensional layered semiconducting materials is becoming pivotal in tailoring their electronic properties, enabling the development of advanced electronic and optoelectronic devices, where the selection of dopant is important. Here, we demonstrate the potential of substitutional vanadium (V) doping in monolayer molybdenum disulfide ($\mathrm{Mo}{\mathrm{S}}_2$) lattice in different extents leading to tunable electronic and optoelectronic properties. We found that low-level V doping (∼1 $\text{at.}\%$) induces $p$-type characteristics in otherwise $n$-type monolayer $\mathrm{Mo}{\mathrm{S}}_2$, whereas medium-level doping (∼5 $\text{at.}\%$) leads to an ambipolar semiconductor. Degenerately doped $\mathrm{Mo}{\mathrm{S}}_2$ (∼9 $\text{at.}\%$) facilitates a transition from semiconducting towards metallic (metal-like) with reduced electrical resistivity (∼4.5 $\mathrm{\Omega }\text{m}$ of $\mathrm{Mo}{\mathrm{S}}_2$ to $\sim 2.2\times {10}^{-5}\mathrm{\Omega }\text{m}$), low activation energy for transport (∼11 meV), and electric field independent drain current in field effect transistor–based transfer characteristics. A detailed temperature- and power-dependent photoluminescence study along with density functional theory–based calculations in support unravels the emergence of an excitonic transition at ∼850 nm with its intensity dependent on the amount of vanadium. This study shows the potential of V doping in $\mathrm{Mo}{\mathrm{S}}_2$ for generating multifunctional two-dimensional materials for next generation electronics, optoelectronics, and interconnects with systematic control over its electronic structure in a wide range.