Shallow donor in natural MoS2.

Using electron paramagnetic resonance and density functional theory calculations, we show that the shallow donor responsible for the n-type conductivity in natural MoS2 is rhenium (Re) with a typical concentration in the low 1017 cm-3 range and the g -values: g|| = 2.0274 and g⊥ = 2.2642. In bulk MoS2, the valley-orbit (VO) splitting and ionization energy of the Re shallow donor are determined to be ~3 meV and ~27 meV, respectively. Calculations show that the VO splitting of Re approaches the value in bulk if the number of MoS2 layers is larger than four and increases to 97.9 meV in a monolayer. [ABSTRACT FROM AUTHOR]