Topological transport and atomic tunnelling–clustering dynamics for aged Cu-doped Bi2Te3 crystals

Abstract

Enhancing the transport contribution of surface states in topological insulators is vital if they are to be incorporated into practical devices. Such efforts have been limited by the defect behaviour of Bi2Te3 (Se3) topological materials, where the subtle bulk carrier from intrinsic defects is dominant over the surface electrons. Compensating such defect carriers is unexpectedly achieved in (Cu0.1Bi0.9)2Te3.06 crystals. Here we report the suppression of the bulk conductance of the material by four orders of magnitude by intense ageing. The weak antilocalization analysis, Shubnikov–de Haas oscillations and scanning tunnelling spectroscopy corroborate the transport of the topological surface states. Scanning tunnelling microscopy reveals that Cu atoms are initially inside the quintuple layers and migrate to the layer gaps to form Cu clusters during the ageing. In combination with first-principles calculations, an atomic tunnelling–clustering picture across a diffusion barrier of 0.57 eV is proposed.

High‐Mobility Sm‐Doped Bi2Se3 Ferromagnetic Topological Insulators and Robust Exchange Coupling

“…Sample Preparation : As in our previous report, the (Sm x Bi 1– x ) 2 Se 3 samples with x = 0, 0.002, 0.005, 0.025, and 0.05 were prepared by the melting method, during which mixed high‐purity Bi, Se, and Sm powders (99.999% purity, Alfa Aesar, in a designed molar ratio) were sealed in clean silica ampoules. The mixtures were then heated to 950 °C throughout one day and kept at this temperature for five days, while being slowly stirred at a speed of 5 turns/minute.…”

Towards higher thermoelectric performance of Bi2Te3 via defect engineering

“…In this system, B atoms act as 0-D defects, i.e., dopants, to contribute charge carriers; grain boundaries act as 2-D defects; and Si grains are 3-D defects. The synergy of defects with different dimensionality greatly enhances the TE performance: charge carriers that donated from dopants flow irreversibly into the host matrix, the mobility is largely retained because the host matrix contains fewer point defects, Electron microscope images of defects observed in Bi2Te3: (e) 0-D Cu dopants [9], (f) 1-D dislocations [10], (g) 2-D grain boundaries [11], (h) 3-D NiTe nanoinclusions [12]. and the final electrical conductivity could be higher than the conductivity of both of the components separately.…”

Roles of Cu in the Enhanced Thermoelectric Properties in Bi0.5Sb1.5Te3

“…In 2011, Liu et al [10] proposed the presence of Cu ions in the van der Waals gap of Bi 2 Te 2.7 Se 0.3 via the characterization and analysis of electrical transport properties and lattice parameters. In 2014, theoretical calculations showed that the formation energy of Cu intercalation in p-type Bi 2 Te 3 is favorable [11]. Another point is that the Cu atoms prefer to enter the Sb sites due to the small electronegativity and radius difference between Cu and Sb [12,13].…”