Thermoelectric power factor enhancement of calcium-intercalated layered silicene by introducing metastable phase

It has been theoretically predicted that the thermoelectric properties of silicene can be enhanced by deforming its atomic structure. In CaSi2, calcium-intercalated layered silicene, the silicene structure of the metastable 3R phase is a deformed silicene structure of the stable 6R phase. In this paper, our first-principle calculation reveals that the Seebeck coefficient is enhanced by transformation from stable 6R- to metastable 3R-CaSi2. We experimentally enhance the Seebeck coefficient by endotaxially introducing metastable 3R-CaSi2 into single-crystalline 6R-CaSi2, leading to a high thermoelectric power factor. This study demonstrates that introducing the metastable phase can become an effective way to enhance the thermoelectric power factor.