Growth and fluorination of CaSi2 thin film

We fabricated bilayer silicene (BLSi) from an epitaxial CaSi2 thin film grown on a Si (111) substrate followed by treatment with BF4--based ionic liquid. First, a 6R-CaSi2 thin film was grown from simultaneously supplied Ca and Si sources. After reacting the CaSi2 thin film with BF4--based ionic liquid, the BLSi was formed. The reaction proceeded laterally along the CaSi2 layer. The rearrangement of the Si and Ca atomic layers in the CaSi2 thin film was investigated by high-angle annular dark-field scanning transmission electron microscope images. (c) 2020 The Japan Society of Applied Physics