Ultrathin septuple layered PbBi2Se4 nanosheets

Abstract

Layered lead bismuth selenide, PbBi2Se4, an intergrowth compound of PbSe (rocksalt) and Bi2Se3 (hexagonal), is a topological insulator in the bulk phase. We present a simple solution based synthesis of two dimensional (2D) few seven atomic (septuple) layered PbBi2Se4 nanosheets (4–7 nm thick) for the first time. The excellent electrical transport in ultrathin PbBi2Se4 is attributed to the presence of dominant surface states that offer high electrical mobility (∼153 cm2 V−1 s−1) and scattering resistant carriers. Ultrathin 3–5 SLs PbBi2Se4 shows an n-type semiconducting behaviour with a band gap of ∼0.6 eV, which is confirmed by optical spectroscopy and thermopower measurements.