Kavli Affiliate: Wei Gao
| First 5 Authors: Fei Shuang, Fei Shuang, , ,
| Summary:
We investigate the kinetics of phase transition between the 2H and
1T$^prime$ phases in monolayer MoTe$_2$ using atomistic simulations based on a
machine learning interatomic potential trained on SCAN-DFT data, combined with
mean field kinetic theory to interpret the underlying mechanisms. The
transition is found to involve both diffusive and diffusionless mechanisms.
Nucleation of 1T$^prime$ phase is initiated by the coalescence of neighboring
Te monovacancies into divacancies, which are found to be mobile and can
interact with other Te vacancies to form small triangular 1T$^prime$ islands.
Growth of these islands proceeds either by incorporating pre-existing vacancies
at the phase boundaries or, in their absence, by absorbing divacancies that
migrate from the surrounding lattice. Once a critical island size is reached,
vacancy-free growth becomes possible although with a higher activation barrier.
Upon removal of external stimuli, the system reverts to 2H phase, during which
Te vacancies reorganize into three-fold spoke-like vacancy lines at the island
center. This reverse process and the subsequent 1T$^prime$$leftrightarrow$2H
reversible transitions are diffusionless, rapid, do not require additional
vacancies and can be driven by mild external stimuli. Although our analysis
focuses on strain-induced transitions, the kinetic mechanisms are expected to
be generalizable to other types of stimuli.
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