Giant Enhancement of Seebeck Coefficient by Deformation of Silicene Buckled Structure in Calcium-Intercalated Layered Silicene Film

Abstract

Layered silicene with deformed buckled structure attracts great interest as a next generation 2D Dirac thermoelectric material beyond conventional layered materials. However, the difficulty of modulating atomic positions in silicene prevents its realization. This study proposes a method to deform buckled structure in layered silicene by controlling the intercalated atoms, which can dramatically enhance its thermoelectric properties. Silicene buckled structure is deformed in epitaxial CaSi2 thin films, Ca-intercalated layered silicenes, on Si(111) substrates, which is related to the composition of intercalated Ca. Therein, buckling height of silicene is changed. This CaSi2 film with deformed silicene exhibits not only metal-like electrical conductivity but also three times larger Seebeck coefficient than the theoretically predicted value, resulting in ≈3000 times larger power factor (≈40 μW cm−1 K−2) than that of the reported CaSi2 film at room temperature. This result experimentally demonstrates that power factor can be greatly enhanced by deforming the silicene buckled structure.