Influence of interstitial V on structure and properties of ferecrystalline ([SnSe]1.15)1(V1+Se2)n for n=1, 2, 3, 4, 5, and 6

Abstract

Cite this article as: M. Falmbigl, D. Putzky, J. Ditto and D.C. Johnson, Influence of interstitial V on structure and properties of ferecrystalline ([SnSe]1.15)1(V1+xSe2)n for n=1, 2, 3, 4, 5, and 6, Journal of Solid State Chemistry, http://dx. AbstractA series of ferecrystalline compounds ([SnSe] 1.15 ) 1 (V 1+x Se 2 ) n with n = 1 -6 and a thin film V 1+x Se 2 were synthesized utilizing the modulated elemental reactant technique. The effect of interstitial V-atoms ranging from 0.13  x  0.42 in different compounds on structure and electrical properties of these intergrowth compounds is reported. The presence of the interstitial V-atoms for n > 1 was confirmed by Rietveld refinements as well as HAADF-STEM cross sections. The off-stoichiometry in the thin film V 1.13 Se 2 causes a suppression of the charge density wave, similar to the effect of non-stoichiometry observed for the bulk compound. The charge density wave of ([SnSe] 1.15 ) 1 (V 1+x Se 2 ) 1, however, is not affected by the non-stoichiometry due to its incorporation as volume inclusions or due to the quasi 2-dimensionality of the isolated VSe 2 layer. In the compounds ([SnSe] 1.15 ) 1 (V 1+x Se 2 ) n with n = 2 -6, the temperature dependence of the electrical resistivity approaches bulk-like behavior.

Atomic-Scale Probing of Reversible Li Migration in 1T-V1+xSe2 and the Interactions between Interstitial V and Li

“…The 1T-V 1+ x Se 2 thin-sheet samples used in this study were cleaved from a bulk crystal by mechanical exfoliation. Small domains with superstructures (e.g., V 5 Se 8 ( x = 0.25) and V 3 Se 4 ( x = 0.5)) randomly distribute in the 1T-VSe 2 ( x = 0) matrix (see Figure S1), which is consistent with the literatures. − Figure a,b is atomically resolved high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images of VSe 2 ( x = 0) nanostructure along the direction of [001] and [100], respectively. No interstitial V atoms have been observed in the VSe 2 ( x = 0) region.…”

“…Here, we use an in situ high-resolution TEM (HRTEM) technique to real-time track the foreign Li insertion and extraction processes in 1T-V 1+ x Se 2 (vanadium diselenide) nanostructures and monitor the structural evolutions. The nonstoichiometric VSe 2 , that is, V 1+ x Se 2 , tends to form self-intercalated compounds, such as V 3 Se 4 and V 5 Se 8 . − For TMDs, when going to the right of the periodic table the d levels (a d-subshell contains d-orbitals inside an atom’s electron shell) progressively decrease in energy and may enter the sulfur or selenium p valence band . Then the d level will be filled at the expense of the valence band, which means that the cations M 4+ are reduced and the anions X 2– are oxidized, resulting in the instability of the compound .…”

“…For vanadium diselenide and vanadium sulfide, the tendency to form self-intercalated compounds M 1+ x X 2 is well-known − ,− because for these cation-rich compounds the interstitial atoms in the van der Waals gap of the layers improve structural stability . So far the structural studies on the system have been performed and the structures of representative compounds such as V 5 Se 8 , V 3 Se 4 , and V 7 Se 8 were reported. , The interstitial V atoms have an important influence on the electric transport, , magnetic properties, and circularly polarized electroluminescence …”

Predicting and Synthesizing Interface Stabilized 2D Layers

“…The resistivity of (Pb 2 MnSe 3 ) 0.6 VSe 2 decreases as the temperature is decreased from room temperature, as expected for a metal, before increasing slowly as the temperature is decreased below ∼150 K. The rate of increasing resistivity accelerates below ∼100 K. The upturn in resistivity at ∼100 K is similar to that found in (PbSe) 1.1 VSe 2 , although the magnitude of the increase is less and the transition is also less abrupt. , The origin of the charge density wave (CDW) in (PbSe) 1.1 VSe 2 is from the VSe 2 monolayer. The signature upturn in resistivity remains if the thickness of the PbSe layer is increased or if PbSe is replaced by SnSe to form the compounds [(SnSe) 1.1 ] m VSe 2 . , The temperature where the upturn occurs varies systematically with the thickness of the SnSe or PbSe layer. , The sharpness of the upturn also varies, presumably as a result of changes in carrier concentration due to defects that form during self-assembly of the precursor. , The CDW found in the compounds with monolayers of VSe 2 is not present if the thickness of the VSe 2 is increased. , The CDW is changed if modulation doping occurs and is completely suppressed for large amounts of charge transfer, for example, in (BiSe)­VSe 2 . CDW transitions in monolayers of VSe 2 have also been reported, and were shown to be sensitive to the heterointerface formed with the substrate. , The rotational disorders present in both (PbSe) 1.1 VSe 2 and (Pb 2 MnSe 3 ) 0.6 VSe 2 prevent direct measurement of structural distortion caused by the localization of conduction electrons .…”

“…37,39 The sharpness of the upturn also varies, presumably as a result of changes in carrier concentration due to defects that form during self-assembly of the precursor. 40,41 The CDW found in the compounds with monolayers of VSe 2 is not present if the thickness of the VSe 2 is increased. 20,42 The CDW is changed if modulation doping occurs 43 and is completely suppressed for large amounts of charge transfer, for example, in (BiSe)VSe 2 .…”