Strain-driven Charge Localisation and Spin Dynamics of Paramagnetic Defects in S-deficit 2H-MoS2 Nanocrystals

A microscopic control over the origin and dynamics of localised spin centres in lower dimensional solids turns out to be a key factor for next generation spintronics and quantum technologies. With the help of low temperature electron paramagnetic resonance (EPR) measurements, supported by the first-principles calculations within density functional theory (DFT) formulation, we found the origin of different high-spin paramagnetic intrinsic charge-centres, Mo3+(4d3) and Mo2+(4d4) present in the nano-crystalline sulfur deficit hexagonal molybdenum disulfide (2H-MoS_(2-x)), against the established notion of spin-1/2 , Mo5+ centres. A critical strain generated in the nano-structured 2H-MoS_(2-x) was found to be very crucial for spin-localization in this layered material. Indeed, computationally effective proposition of the PBE+U exchange-correlations within DFT including D3-dispersion corrections found to be more viable than expensive higher rung of exchange-correlation functionals, explored earlier. It is also found that the oxygen vacancy of the reduced oxide phase, embedded in 2H-MoS_(2-x) host lattice, has the longest relaxation times. Moreover, the temperature dependence of spin-lattice relaxation measurements reveals a direct process for interstitial spin centres and a Raman process for both sulfur and oxygen vacancy sites. We expect such observation would be a valuable pillar for better understanding of the next generation quantum technologies and device applications.