Electrochemically exfoliated thin Bi ₂ Se ₃ films and van der Waals heterostructures Bi ₂ Se ₃ /graphene

Abstract

Abstract Thin Bi 2 Se 3 flakes with few nanometer thicknesses and sized up to 350 μ m were created by using electrochemical splitting from high-quality Bi 2 Se 3 bulk monocrystals. The dependence of film resistance on the Bi 2 Se 3 flake thickness demonstrates that, at room temperature, the bulk conductivity becomes negligible in comparison with the surface conductivity for films with thicknesses lower than 80 nm. Unexpectedly, all these films demonstrated p-type conductivity. The doping effect with sulfur or sulfur-related radicals during electrochemical exfoliation is suggested for the p-type conductivity of the exfoliated Bi 2 Se 3 films. The formation of 2–8 nm films was predominantly found. Van der Waals (vdW) heterostructures of Bi 2 Se 3 /Graphene/SiO 2 /Si were created and their properties were compared with that of Bi 2 Se 3 on the SiO 2 /Si substrate. The increase of the conductivity and carrier mobility in Bi 2 Se 3 flakes of 3–5 times was found for vdW heterostructures with graphene. Thin Bi 2 Se 3 films are potentially interesting for applications for spintronics, nano- and optoelectronics.