Topological insulators have conducting states at their edges and surfaces even though they have a bulk band gap.Since these materials have bulk band gap and topologically protected surface states, they present an exotic playground for both electronic and morphologic investigations[1].

In our work, we have been working on a natural topological insulator Bi₂Te₃ crystals. Bi₂Te₃ has a rhombohedral crystal structure with lattice constants (a) and (c) 0.438nm and 3.03nm respectively. The atomic order consist of layered structure in these quence of Te(1)-Bi-Te(2)-Bi-Te(1) along the c-axis. These five atomic planes are named as a ‘quintuple’.

Scanning Tunneling Microscopy (STM) and Spectroscopy (STS) is instrumental in characterizing the atomic defects besides the local electronic structure. Apart from this, works ate larges scale are in progress to make new devices using this material.

Atomic resolution image of cleaved Bi₂Te₃ surface acquired by STM. Tunneling junction parameters were 500 mV, 400 pA. Topography image shows the vacancy defects on Te-1 surfaces and corresponding model is given in the inset.

Reference:

[1] Chen et al., 2009,Science,325 (5937): 178-181