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.