Strain-driven Charge Localisation and Spin Dynamics of Paramagnetic Defects in S-deficit 2H-MoS2 Nanocrystals
arxiv(2023)
摘要
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.
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