Modular Design via Multiple Anion Chemistry of the High Mobility van der Waals Semiconductor Bi₄O₄SeCl₂

Abstract

Making new van der Waals materials with electronic or magnetic functionality is a chemical design challenge for the development of two-dimensional nanoelectronic and energy conversion devices. We present the synthesis and properties of the van der Waals material Bi4O4SeCl2, which is a 1:1 superlattice of the structural units present in the van der Waals insulator BiOCl and the three-dimensionally connected semiconductor Bi2O2Se. The presence of three anions gives the new structure both the bridging selenide anion sites that connect pairs of Bi2O2 layers in Bi2O2Se and the terminal chloride sites that produce the van der Waals gap in BiOCl. This retains the electronic properties of Bi2O2Se while reducing the dimensionality of the bonding network connecting the Bi2O2Se units to allow exfoliation of Bi4O4SeCl2 to 1.4 nm height. The superlattice structure is stabilized by the configurational entropy of anion disorder across the terminal and bridging sites. The reduction in connective dimensionality with retention of electronic functionality stems from the expanded anion compositional diversity.

Fast lithium-ion conductivity in the ‘empty-perovskite’ n = 2 Ruddlesden–Popper-type oxysulphide Y2Ti2S2O5

“…We speculate that this mechanism may contribute to the excellent photocatalytic activity of Y 2 Ti 2 S 2 O 5 and Sm 2 Ti 2 S 2 O 5 . 52,83 With advances in the design 84 and modular synthesis of layered mixed-anion semiconductors, 85 it may be possible to employ this strategy for the design of improved photocatalysts that efficiently separate charges and maximise carrier lifetimes.…”

Shift–Twin Option in Eight-Layer Hexagonal Perovskite Niobates Ba8MNb6O24

“…However, the entropy change could probably play a dominant role in lowering the Gibbs free energy (ΔG = ΔH − TΔS) over the enthalpy change, as recently reported in the stabilization of layered material Bi 4 O 4 SeCl 2 . 31 Thus the formation of a twinned structure may be allowed even the shifted structure is enthalpy favorable over the twinned structure.…”

Low thermal conductivity in a modular inorganic material with bonding anisotropy and mismatch

“…4A). Bi 4 O 4 SeCl 2 can be described as a bulk superlattice of BiOCl, with contrasting strong and weak bonding interfaces and Bi 2 O 2 Se containing an undersized bridging Se layer, with its associated distortion-prone interface arising from the in-plane structural instability, and is experimentally stabilized by Se/Cl site mixing ( 38 ). This extended structure should therefore combine the ingredients of Fig.…”