Superseding van der Waals with Electrostatic Interactions: Intercalation of Cs into the Interlayer Space of SiAs₂

Cs _yM _xSi_{1- x}As₂ (M = Cu, Zn, or Ga; y = 0.15-0.19; x depends on M) represents a new group of pseudo-two-dimensional compounds that allow property tuning with various metal substituents without alteration of the main Si-As two-dimensional framework. Their crystal structure is built from M _xSi_{1- x}As₂ layers separated by disordered chains of Cs cations. These compounds are synthesized using a CsCl flux as a source of Cs, circumventing the need for an expensive and air-sensitive Cs metal reagent. M-Si substitution is required to compensate for the excess electrons donated by Cs cations. Alternatively, the charge compensation can be achieved by the formation of As vacancies. Resistivity measurements confirm the electron-balanced nature of the compounds that exhibit semiconducting behavior with small bandgaps.