Growth of topological insulator nanoparticles by droplet epitaxy

Topological insulators (TIs) are a class of materials which exhibit unique electronic states delocalized on the outer surface of the material. Due to the strong spin-orbit coupling in TIs, these states are spin-polarized and robust against scattering. The robust nature of these states could present a potential solution to the problem of decoherence in qubits. This has motivated research into creating quantum information storage/transport devices using TIs. In order to create such a device, we first must understand how to isolate these states energetically, and this can be done using quantum confinement. Our first step involves the creation of quantum confined TIs. Here, we report on the growth of TI quantum dots grown by droplet epitaxy. We chose the TI Bi2Se3, a commonly studied 3D topological insulator, and growths were performed on GaAs in a molecular beam epitaxy chamber. We varied the growth conditions of bismuth deposition time and substrate temperature to determine the degree to which TI nanoparticle dimensions could be controlled. Within the growth window, we observed particles in the range of 5-15 nm tall and 500-3000 nm2 in area (equivalent circular radius ~12-30 nm). We observed various trends in particle height, area, density and polydispersity as a result of varying growth conditions and adjusting the growth procedure (ex. adding a long anneal step between bismuth and selenium deposition steps). Overall, these results will be helpful in aiding further development of topological insulator devices.