Substitutional transition metal doping in MoS2: a first-principles study

Single-layer MoS 2 is a direct-gap semiconductor whose band edges character is dominated by the d-orbitals of the Mo atoms. It follows that substitutional doping of the Mo atoms has a significant impact on the material’s electronic properties, namely the size of the band gap and the position of the Fermi level. Here, density functional theory is used along with the G 0 W 0 method to examine the effects of substituting Mo with four different transition metal dopants: Nb, Tc, Ta, and Re. Nb and Ta possess one less valence electron than Mo does and are therefore p-type dopants, while Re and Tc are n-type dopants, having one more valence electron than Mo has. Four types of substitutional structures are considered for each dopant species: isolated atoms, lines, three-atom clusters centered on a S atom (c3s), and three-atom clusters centered on a hole (c3h). The c3h structure is found to be the most stable configuration for all dopant species. However, electronic structure calculations reveal that isolated dopants are preferable for efficient n- or p-type performance. Lastly, it is shown that photoluminescence measurements can provide valuable insight into the atomic structure of the doped material. Understanding these properties of substitutionally-doped MoS 2 can allow for its successful implementation into cutting-edge solid state devices.