Phase transitions between polytypes and intralayer superstructures in transition metal dichalcogenides

Katzke, Hannelore; Tolédano, Pierre; Depmeier, Wulf

doi:10.1103/physrevb.69.134111

Cited by 86 publications

(84 citation statements)

References 23 publications

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“…In 2H a stacking, one transition metal atom is always on top of another transition According to previous literature on TMDCs [32,33].…”

Section: H Polytypementioning

confidence: 97%

“…There are several other polytypes for stacks of more than two TLs, and at least 11 polytypes were identified in TMDCs [33]. For example, the unit cell of the 3R-MoS 2 (with the stacking /AbA BcB CaC/) [32,33] comprises nine atoms in three TLs.…”

Section: A Real Space Symmetrymentioning

confidence: 99%

“…For example, the unit cell of the 3R-MoS 2 (with the stacking /AbA BcB CaC/) [32,33] comprises nine atoms in three TLs. The treatment of these polytypes with a high number of TLs is beyond the scope of this work, but for the 3R case, Table I summarizes some symmetry considerations and gives representative TMDC examples.…”

Section: A Real Space Symmetrymentioning

confidence: 99%

“…The 2H bulk polytype can assume two forms with different stacking symmetries: 2H a (or /AbA CbC/ stacking) [32,33], and 2H c (/CaC AcA/ stacking) [33]. In 2H a stacking, one transition metal atom is always on top of another transition According to previous literature on TMDCs [32,33].…”

Section: H Polytypementioning

confidence: 99%

“…Group theory has already been used to describe the structure of TMDCs in the bulk form for different polytypes [32,33], in the few-TL 2H c polytype for zone center phonons (at the BZ point) [23][24][25] and for the electronic structure at the and K points [34], and for a more detailed understanding of some nonlinear optical processes [26]. In this work, group theory is applied to TMDCs in both the trigonal prismatic (H ) and octahedral (T ) metal atom coordinations, considering the stacking order for 2H a and 2H c for H , and 1T for T , and the dependence on the number of layers N (even or odd), and considering the full set of wave vectors in the BZ, i.e., going beyond the zone center.…”

Section: Introductionmentioning

confidence: 99%

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Group theory analysis of phonons in two-dimensional transition metal dichalcogenides

et al. 2014

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Transition metal dichalcogenides (TMDCs) have emerged as a new two-dimensional material's field since the monolayer and few-layer limits show different properties when compared to each other and to their respective bulk materials. For example, in some cases when the bulk material is exfoliated down to a monolayer, an indirect-to-direct band gap in the visible range is observed. The number of layers N (N even or odd) drives changes in space-group symmetry that are reflected in the optical properties. The understanding of the space-group symmetry as a function of the number of layers is therefore important for the correct interpretation of the experimental data. Here we present a thorough group theory study of the symmetry aspects relevant to optical and spectroscopic analysis, for the most common polytypes of TMDCs, i.e., 2H a, 2H c and 1T , as a function of the number of layers. Real space symmetries, the group of the wave vectors, the relevance of inversion symmetry, irreducible representations of the vibrational modes, optical activity, and Raman tensors are discussed.

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“…In 2H a stacking, one transition metal atom is always on top of another transition According to previous literature on TMDCs [32,33].…”

Section: H Polytypementioning

confidence: 97%

Section: A Real Space Symmetrymentioning

confidence: 99%

Section: A Real Space Symmetrymentioning

confidence: 99%

Section: H Polytypementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Group theory analysis of phonons in two-dimensional transition metal dichalcogenides

et al. 2014

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Extraordinarily Strong Interlayer Interaction in 2D Layered PtS₂

et al. 2016

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Platinum disulfide (PtS2 ), a new member of the group-10 transition-metal dichalcogenides, is studied experimentally and theoretically. The indirect bandgap of PtS2 can be drastically tuned from 1.6 eV (monolayer) to 0.25 eV (bulk counterpart), and the interlayer mechanical coupling is almost isotropic. It can be explained by strongly interlayer interaction from the pz orbital hybridization of S atoms.

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Highly Efficient Uniaxial In‐Plane Stretching of a 2D Material via Ion Insertion

et al. 2021

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On‐chip dynamic strain engineering requires efficient micro‐actuators that can generate large in‐plane strains. Inorganic electrochemical actuators are unique in that they are driven by low voltages (≈1 V) and produce considerable strains (≈1%). However, actuation speed and efficiency are limited by mass transport of ions. Minimizing the number of ions required to actuate is thus key to enabling useful “straintronic” devices. Here, it is shown that the electrochemical intercalation of exceptionally few lithium ions into WTe2 causes large anisotropic in‐plane strain: 5% in one in‐plane direction and 0.1% in the other. This efficient stretching of the 2D WTe2 layers contrasts to intercalation‐induced strains in related materials which are predominantly in the out‐of‐plane direction. The unusual actuation of LixWTe2 is linked to the formation of a newly discovered crystallographic phase, referred to as Td', with an exotic atomic arrangement. On‐chip low‐voltage (<0.2 V) control is demonstrated over the transition to the novel phase and its composition. Within the Td'‐Li0.5−δWTe2 phase, a uniaxial in‐plane strain of 1.4% is achieved with a change of δ of only 0.075. This makes the in‐plane chemical expansion coefficient of Td'‐Li0.5−δWTe2 far greater than of any other single‐phase material, enabling fast and efficient planar electrochemical actuation.

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Phase transitions between polytypes and intralayer superstructures in transition metal dichalcogenides

Cited by 86 publications

References 23 publications

Group theory analysis of phonons in two-dimensional transition metal dichalcogenides

Group theory analysis of phonons in two-dimensional transition metal dichalcogenides

Extraordinarily Strong Interlayer Interaction in 2D Layered PtS₂

Highly Efficient Uniaxial In‐Plane Stretching of a 2D Material via Ion Insertion

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Phase transitions between polytypes and intralayer superstructures in transition metal dichalcogenides

Cited by 86 publications

References 23 publications

Group theory analysis of phonons in two-dimensional transition metal dichalcogenides

Group theory analysis of phonons in two-dimensional transition metal dichalcogenides

Extraordinarily Strong Interlayer Interaction in 2D Layered PtS2

Highly Efficient Uniaxial In‐Plane Stretching of a 2D Material via Ion Insertion

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Product

Resources

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Extraordinarily Strong Interlayer Interaction in 2D Layered PtS₂