Figure 1: SEM, STM, LEED and sheet conductance of Bi2Se3 on Si(111).
From: Nanoscale electron transport at the surface of a topological insulator
(a) Scheme of the STP experiment: a voltage Vtrans leading to a transverse current Itrans is applied to the sample by two tips (red circuit). A potentiometer connects the tunnelling tip to the sample contacts in a Wheatstone bridge circuit. Vloc represents the local potential at the surface under the tunnelling tip. (b) SEM image of the contact geometry. Scale bar, 75 μm. Two Au tips contact the Bi2Se3 sample surface. A W tip is operated in tunnelling distance (tunnelling tip) and simultaneously maps the surface structure and the electrochemical potential. (c) STM image of the 14 QL Bi2Se3 film on Si(111) (Vt=1 V, It=12 pA, 650 × 650 nm2). Scale bar, 100 nm. The surface of the Bi2Se3 film is crystalline and flat. The inset shows the hexagonal LEED pattern of the Bi2Se3 film at 35 eV (lattice constant of 0.41±0.01 nm) exhibiting the high crystallinity of the film. (d) Distance-dependent resistance measurement of the Bi2Se3 film, leading to a sheet conductance of 1.8±0.1 mS. The inset shows SEM image snapshots of the measuring process. Scale bar, 75 μm.
