Structural stability of coplanar 1T-2H superlattice MoS₂under high energy electron beam

Abstract

Coplanar heterojunctions composed of van der Waals layered materials with different structural polymorphs have drawn immense interest recently due to low contact resistance and high carrier injection rate owing to low Schottky barrier height. Present research has largely focused on efficient exfoliation of these layered materials and their restacking to achieve better performances. We present here a microwave assisted easy, fast and efficient route to induce high concentration of metallic 1T phase in the original 2H matrix of exfoliated MoS layers and thus facilitating the formation of a 1T-2H coplanar superlattice phase. High resolution transmission electron microscopy (HRTEM) investigations reveal formation of highly crystalline 1T-2H hybridized structure with sharp interface and disclose the evidence of surface ripplocations within the same exfoliated layer of MoS. In this work, the structural stability of 1T-2H superlattice phase during HRTEM measurements under an electron beam of energy 300 keV is reported. This structural stability could be either associated to the change in electronic configuration due to induction of the restacked hybridized phase with 1T- and 2H-regions or to the formation of the surface ripplocations. Surface ripplocations can act as an additional source of scattering centers to the electron beam and also it is possible that a pulse train of propagating ripplocations can sweep out the defects via interaction from specific areas of MoS sheets.

Coexisting 1T/2H polymorphs, reentrant resistivity behavior, and charge distribution in MoS2−hBN 2D/2D composite thin films

“…Therefore, in the 1T case the diffraction spots are usually angularly shifted from there ideal place in the basal plane by 30° (yellow line). [36] As stated by Reshmi et al, [37] the dspacing of 2.34 Å (Fig. 5e) closely corresponds to (2 0 1) As stated above, the HRTEM images of Fig.…”

Direct synthesis of metastable phases of 2D transition metal dichalcogenides

“…Among the emerging approaches to induce the 2H-to-1T phase transformation in group VI TMDs, we would like also to mention the microwave plasma treatment 131,132 and the supercritical CO 2 treatment. 133,134 These less conventional approaches allow for a controllable phase engineering also in the liquid phase.…”

“…134 Similar to supercritical CO 2 treatment, mild microwave plasma treatment has been reported to introduce the 1T phase domains in the exfoliated 2H MoS 2 nanosheets. 132 C. Sharma et al have used forming gas microwave plasma to convert exfoliated 2H MoS 2 flakes into the 1T phase with a 70% efficiency. The phase transition is assumed to proceed due to the momentum transfer from the plasma ions to the MoS 2 lattice, causing the chalcogen plane gliding.…”

Construction of 1T@2H MoS2 heterostructures in situ from natural molybdenite with enhanced electrochemical performance for lithium-ion batteries

“…In contrast, aer the expansion of molybdenite concentrate, the dispersion was gray, and the exciton peaks at A and B were not apparent, which also proved the existence of 1T MoS 2 . 38,39 Moreover, XPS semi-quantitative method was used to verify that the 1T phase was produced in 1T@2H MoS 2 , and the relative content ratio of the 2H and 1T phase was determined by analysis. 34 AS shown in Fig.…”