Influence of Nanoarchitectures on Interlayer Interactions in Layered Bi–Mo–Se Heterostructures

Abstract

Recently, it was shown that the metastable heterostructure (Bi-Se) 0.97 MoSe 2 , consisting of alternating bilayers of BiSe and MoSe 2 trilayers, contained both the semiconducting 2H-and the metallic 1T-polytype of MoSe 2 . In this study, we investigated five other structures containing different stackings of BiSe, Bi 2 Se 3 , and MoSe 2 layers in the repeat unit to understand what facilitates the stabilization of metastable constituent layers. X-ray diffraction was used to characterize the stacking sequences and the structure of the different layers, and X-ray photoelectron spectroscopy and Raman spectroscopy were carried out to understand the occurring interlayer interactions. A sufficient transfer of electrons from the BiSe layers into MoSe 2 is required to form 1T-MoSe 2 upon crystallization. The yield of 1T-MoSe 2 is reduced if charges are localized at antiphase boundaries in BiSe or if filling of conduction band states in Bi 2 Se 3 or 2H-MoSe 2 occurs. If the repeat unit contains more than one layer of MoSe 2 , band structure changes allow charges from BiSe to be distributed over all available dichalcogenide layers, suppressing the formation of both 1T-MoSe 2 and antiphase boundaries. Understanding the interplay between the different layers may enable the design of heterostructures with the desired constituent structure and properties.

2 + 2 = 3: Making Ternary Phases through a Binary Approach

“…One approach used for the synthesis of complex ternary phases is to avoid the formation of these binary intermediates altogether. − By depositing the elements into a thin, ordered film, the diffusion path length of all of the elements can be minimized. As this ordered amorphous film is then annealed, the layers react and directly form the desired ternary product with very high purity.…”

Modulation doping and charge density wave transition in layered PbSe–VSe2 ferecrystal heterostructures

“…Deviations from the expected bulk compositions are due to the limited information depth of XPS measurements, especially when the repeat unit thickness is of the same order of magnitude as the inelastic mean free path of the photoelectrons. 58 The error bars in Fig. 3 illustrate the variations in composition that are observed at different cleavage planes for the same sample types (symbols indicate the respective average values).…”

“…X-ray and UV photoelectron spectroscopy (XPS, UPS) can give valuable insights into the interlayer interactions in ferecrystals, especially charge transfer mechanisms, as was demonstrated previously. 56–58 [(PbSe) 1+ δ ] m [VSe 2 ] 1 ferecrystals with m = 1–4 and [(PbSe) 1+ δ ] 1 [VSe 2 ] n ferecrystals ( n = 1–3) have been investigated, as well as a binary sample of VSe 2 that was also prepared via the MER synthesis. In the following, individual ferecrystal samples will be abbreviated by their characteristic stacking sequence ( m , n ).…”

Substituent Effects in the Synthesis of Heterostructures

“…[(Bi 2 Se 3 ) 1+δ ] 1 [(MoSe 2 )] 1 forms from Mo|Se|Bi|Se precursors when they contain the stoichiometric amount of Bi and Mo and excess Se. Presumably, the excess amounts of Se in Mo|Se|Bi|Se reduce the amount of charge transfer from Bi to Mo, resulting in the nucleation and growth of 2H-MoSe 2 , which is the only polymorph observed in the XPS of [(Bi 2 Se 3 ) 1+δ ] n [(MoSe 2 )] 1 compounds . Mixtures of [(BiSe) 1+γ ] 1 [(MoSe 2 )] 1 and [(Bi 2 Se 3 ) 1+δ ] 1 [(MoSe 2 )] 1 form if there is not sufficient excess Se.…”

“…The MoSe 2 in [(BiSe) 1+γ ] 1 [(MoSe 2 )] 1 is a mix of semiconducting 2H and metallic 1T polymorphs . The MoSe 2 layered with Bi 2 Se 3 is only the semiconducting 2H polymorph . These results suggest that ″substituent-like″ electronic effects exist in the synthesis of extended solids, impacting the reaction pathway.…”