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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.
Highlights
Enhancing the transport contribution of surface states in topological insulators is vital if they are to be incorporated into practical devices
We introduce an ageing method to (Cu0.1Bi0.9)2Te3.06 crystals whereby intense ageing leads to a great suppression of the bulk conductance of up to four orders of magnitude
The Fermi level is observed to move inside the bandgap, and no sizeable impurity band (IB) can be observed by the scanning tunnelling microscopy (STM)
Summary
Enhancing the transport contribution of surface states in topological insulators is vital if they are to be incorporated into practical devices. Doping by 0.1% can already suppress the bulk carrier concentration, a serious concern is that the Fermi level will further shift owing to the migration of the dopant atoms after the optimized TSS has been achieved[21,22,23]. All the above evidence points to an observable TSS-related electron transport in our aged Cu-doped Bi2Te3 bulk crystals.
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