Electronic properties of (Sb;Bi)₂Te₃ colloidal heterostructured nanoplates down to the single particle level

We investigate the potential use of colloidal nanoplates of Sb₂Te₃ by conducting transport on single particle with in mind their potential use as 3D topological insulator material. We develop a synthetic procedure for the growth of plates with large lateral extension and probe their infrared optical and transport properties. These two properties are used as probe for the determination of the bulk carrier density and agree on a value in the 2-3 × 10¹⁹ cm^-3 range. Such value is compatible with the metallic side of the Mott criterion which is also confirmed by the weak thermal dependence of the conductance. By investigating the transport at the single particle level we demonstrate that the hole mobility in this system is around 40 cm²V^-1s^-1. For the bulk material mixing n-type Bi₂Te₃ with the p-type Sb₂Te₃ has been a successful way to control the carrier density. Here we apply this approach to the case of colloidally obtained nanoplates by growing a core-shell heterostructure of Sb₂Te₃/Bi₂Te₃ and demonstrates a reduction of the carrier density by a factor 2.5.