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 _parallel = 2.0274 and g _{perpendicular to} = 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. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)