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

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 cm2V−1s−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 SrAl2Si2with 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.