Interface‐Driven Structural Distortions and Composition Segregation in Two‐Dimensional Heterostructures

Abstract

The discovery of emergent phenomena in 2D materials has sparked substantial research efforts in the materials community. A significant experimental challenge for this field is exerting atomistic control over the structure and composition of the constituent 2D layers and understanding how the interactions between layers drive both structure and properties. While no segregation for single bilayers was observed, segregation of Pb to the surface of three bilayer thick PbSe-SnSe alloy layers was discovered within [(Pb Sn Se) ] (TiSe ) heterostructures using electron microscopy. This segregation is thermodynamically favored to occur when Pb Sn Se layers are interdigitated with TiSe monolayers. DFT calculations indicate that the observed segregation depends on what is adjacent to the Pb Sn Se layers. The interplay between interface- and volume-free energies controls both the structure and composition of the constituent layers, which can be tuned using layer thickness.

The Spatially Oriented Charge Flow and Photocatalysis Mechanism on Internal van der Waals Heterostructures Enhanced g-C3N4

“…Recent advances in constructing van der Waals heterostructures (VDWHs) have provided unprecedented opportunities to precisely manipulate the electronic structure of 2D materials. − Such VDWHs are made by assembling two or more different 2D crystals (monolayer or multilayers) with the controlled stacking sequences. Since chemical composition and electronic structure of each component can be rationally designed, one can tune the charge displacement and flow orientation at the heterostructure interface. − The possibility of making multilayer VDWHs has been demonstrated experimentally, using graphene, MoS 2 and hexagonal boron nitride (h-BN) as building blocks. − Although they exhibit oriented charge transfer crossing the heterostructure interface, traditional VDWHs still suffer from low efficiency in separating and transferring oriented charges in each component’s multilayer structure because of the weakness of vdW forces between adjacent layers. − …”

Two‐Dimensional Transition Metal Oxides and Chalcogenides for Advanced Photocatalysis: Progress, Challenges, and Opportunities

“…Among known photocatalysts, transition metal oxides (TMOs) and transition metal chalcogenides (TMCs) comprise a popular category, as a result of their tunable structure, high stability, low cost, Earth abundance, and appealing catalytic activity, along with a large number of different compounds in this category. [ 5 ] As of today, various TMOs and TMCs have been explored and implemented for diverse photocatalytic reactions, including Cu 2 O, [ 6 ] ZnO, [ 7 ] NiO, [ 8 ] Mn 3 O 4 , [ 9 ] Co 3 O 4 , [ 10 ] Fe 2 O 3 , [ 11 ] CeO 2 , [ 12 ] ZrO 2 , [ 13 ] TiO 2 , [ 14 ] ZnIn 2 S 4 , [ 15 ] CdS, [ 16 ] MnS, [ 17 ] PbS, [ 18 ] NiS 2 , [ 19 ] WS 2 , [ 20 ] TiS 2 , [ 21 ] FeCoS 2 –CoS 2 , [ 22 ] Mo/NiS 2 , [ 23 ] MoS, [ 24 ] Cu 2 MoSe 4 , [ 25 ] NiSe 2 , [ 26 ] CoSe 2 , [ 27 ] Pb x Sn 1− x Se, [ 28 ] etc.…”

Synthesis of Tunable SnS-TaS2 Nanoscale Superlattices

“…While misfit compounds display a number of exotic properties as a result of their construction, they are thermodynamic in nature and limited to architectures in which n = 1, 2 and m = 1, thus precluding investigation of property tunability via a full series of variably stacked materials. However, as self-assembled analogues to misfit compounds, chalcogenide thin film superlattices formed from designed precursors remove thermodynamic constraints, allowing the study of systematic changes in structure and properties as a function of precise changes to the stacking sequences (i.e., m , n = 1, 2, 3, 4, ...) and strategic control of dopants. − Reports have revealed the tunability of properties relevant to a number of technologically promising applications, including surveying architectural effects on thermoelectric performance, , charge density wave transitions, − and superconductivity onset …”