Invited Paper NM-TuM11
Growth and In situ Electronic Transport and Scanning Probe Studies of Topological Materials Bi₂Se₃ and Na₃Bi

Tuesday, December 13, 2016, 11:20 am, Room Hau

Topological materials are fascinating novel electronic phases with important device implications. Topological insulators are insulating in their interiors but conduct on their boundaries; two-dimensional topological insulators can realize dissipationless conduction along their one-dimensional edges. Topological Dirac semimetals lie at the boundary between conventional and topological insulators, and can be pushed toward one or the other by electric or magnetic fields, realizing new types of switches.

I will discuss the development of a novel experimental capability combining the growth of topological materials by molecular beam epitaxy (MBE) with in situ magnetotransport and low-temperature scanning tunneling microscopy at 5 K. This capability has been used to study the transport properties of topological insulator Bi₂Se₃ in situ during MBE growth, monitoring the carrier concentration and mobility as a function of film thickness[1]. More recently, topological Dirac semimetal Na₃Bi thin films have been prepared on α-Al₂O₃(0001) substrates with low temperature charge carrier mobilities exceeding 6000 cm²V^-1s^-1 with n-type carrier densities below 1 x 10¹⁸ cm^-3, comparable to the best single crystal values[2]. Perpendicular magnetoresistance at low field shows the perfect weak-antilocalization behaviour expected for Dirac fermions in the absence of intervalley scattering. Our ongoing efforts to tune the carrier density using physical and chemical schemes to realize topological devices will also be discussed [3].

References

1. Jack Hellerstedt et al., Appl. Phys. Lett. 105, 173506 (2014).

2. J. Hellerstedt et al., Nano Lett. 16, 3210 (2016).

3. M.T. Edmonds et al., ACS Appl. Mater. Interfaces 8, 16412 (2016).