Spontaneous curling of freestanding Janus monolayer transition-metal dichalcogenides

Abstract

In this paper, using molecular dynamics simulations we report spontaneous curling behaviors of freestanding Janus monolayer S-Mo-Se (MoSeS) structures. Density functional theory calculations are performed to obtain the phonon dispersion and phonon spectra of the Janus monolayer MoSeS for analyzing its structural stability. The results show that the Janus monolayer MoSeS is structurally stable. Due to the lattice mismatch between MoS and MoSe domains, the Janus monolayer MoSeS at the freestanding state always spontaneously rolls up in a constant temperature and pressure system. The direction of curling is preferred along the armchair orientation. Specifically, as for the Janus monolayer MoSeS whose size is larger than ∼30 nm, it can spontaneously roll up into a nanotube structure. The underlying physical mechanisms of these phenomena are well uncovered by using classical Timoshenko plate theory and the minimum energy principle.

Engineered 2D Transition Metal Dichalcogenides—A Vision of Viable Hydrogen Evolution Reaction Catalysis

“…[ 97 ] More careful preparations and experiments have been conducted on the Janus TMDs with controlled chalcogen substitution where one chalcogen layer is fully replaced by a different chalcogen. [ 120–126 ] One of the most studied version of these, the monolayered S‐Mo‐Se, can be considered as the MoS 2 monolayer with one Se substitutional doping layer ( Figure 8 a). [ 122 ] In the Janus structure, the breaking of structural symmetry gives large intrinsic lattice strain, and has significant effects in altering the band‐structure for distinctive physical and chemical properties.…”

Band structure of MoSTe Janus nanotubes

“…Such layers can, at least in principle, be obtained by substitution of the chalcogen atoms on one side of a regular MX 2 monolayer, and examples include MoSSe, MoSTe, and WSSe, among which MoSSe was recently synthesized [17]. TMD Janus monolayers are particularly interesting because their asymmetry gives rise to an intrinsic strain, which makes self-rolling into the nanotube structure energetically favorable [18,19]. In contrast to the multiwalled nanotubes mentioned above, such nanotubes are expected to be stable as single-walled structures with diameters of only a few nanometers.…”

Vacancy‐Induced Oxygen Reduction Activity in Janus Transition Metal Dichalcogenides

“…Recently, a new family of TMDs, Janus transition metal dichalcogenide monolayers (Janus TMDs, MXY, X≠Y) have been synthesized based on either MoS 2 or MoSe 2 monolayer by using the chemical vapor deposition (CVD) method . Since then, various kinds of 2D Janus TMDs have been investigated theoretically . Unlike the conventional TMDs, Janus TMDs can break the intrinsic in‐plane symmetry and out‐of‐plane mirror symmetry directly, resulting in enhanced in‐plane piezoelectricity and additional out‐of‐plane piezoelectricity .…”