posted on 2024-02-14, 20:35authored byShiyu Xu, Mengjing Wang, Maria Bambrick-Santoyo, Kenneth Evans-Lutterodt, Natalie L. Williams, Judy J. Cha
A new
polytype of WTe2 with a bandgap has been recently
discovered through the intercalation of lithium into the van der Waals
gaps of Td-WTe2. Here, we report
the effects of reduced thicknesses and heterointerfaces on the intercalation-induced
phase transition in WTe2. Using in situ Raman spectroscopy during the electrochemical lithiation of WTe2 flakes as a function of flake thickness, we observe that
additional electrochemical energy is required for the phase transition
of WTe2 from the Td phase to
the new lithiated Td′ phase, going
from 0.8 V of the applied electrochemical voltage for a thick flake
to 0.5 V and 0.3 V for 7- and 5-layered samples, respectively. We
ascribe this suppression of the phase transition to the interfacial
interaction between the nanoflake and SiO2/Si substrate,
which plays an increasing role as the sample thickness is reduced.
The suppressed kinetics of the phase transition can be mitigated by
placing the WTe2 flake on a hexagonal boron nitride (hBN)
flake, which facilitates the release of the in-plane strain induced
by the phase transition. Our study underscores the significance of
interfacial effects in modulating phase transitions in two-dimensional
(2D) materials, suggesting heterogeneous transition pathways, as well
as interfacial engineering to control these phase transitions.