Nanoscale synthesis of ionic analogues of bilayer silicene with high carrier mobility

Abstract

Design of materials with special properties benefits from establishing deep structural and electronic analogies between emerging and existing materials. The Zintl anion [Al₂Si₂]²⁻ is both isostructural and isoelectronic to bilayer silicene; it thus makes a promising building block to assemble electronic materials. Here, we show that nanoscale films of SrAl₂Si₂, a semimetal formed by alternating [Al₂Si₂] and Sr layers, exhibit a high carrier mobility, exceeding 10 000 cm² V⁻¹ s⁻¹. The dominant role of the anionic bilayers in the electronic structure and transport properties is established by band structure calculations. To synthesize monocrystalline epitaxial films of SrAl₂Si₂ with atomically sharp interfaces, a general two-step route involving a sacrificial 2D template is devised. A distinct advantage of the films is their natural integration with silicon technology. The results establish a platform for engineering layered ionic nanomaterials.