Self-assembled Bismuth Selenide (Bi₂Se₃) quantum dots grown by molecular beam epitaxy

Three-dimensional topological insulators (TIs) are insulators in the bulk with surface states that have spins locked with momentum and are protected by time-reversal symmetry. Control of these states can be useful for novel applications in quantum computing and spintronics. Some properties of these materials can be enhanced by electronic confinement in quantum dots (QDs)^1,2. Bi₂Se₃ is particularly interesting since its band gap is relatively large and the experimentally verified Dirac cone is in the Γ-point. Bi₂Se₃ has been grown successfully by molecular beam epitaxy (MBE) on different substrates, and a lithographically defined QD with quantum confinement was previously demonstrated³. We report the growth of self-assembled Bi₂Se₃ QDs by MBE using the droplet epitaxy technique. The QDs form after anneal of Bi droplets under a Se flux. They are crystalline and have average dimensions of 12-nm height (12 quintuple layers) and 46-nm width, and a density of 8.5x10⁹ cm^-2. The QD formation process developed is simple, reproducible and tunable.

1. Herath, T. M. et al. J. Phys. Condens. Matter 26, 115302 (2014).
2. Paudel, H. P. et al, M. N. Phys. Rev. B 88, 085316 (2013).
3. Cho, S. et al. Nano Lett. 12, 469 (2012).