Optimization of the Growth of the Van der Waals Materials Bi₂Se₃ and (Bi_0.5In_0.5)₂Se₃ by Molecular Beam Epitaxy

Abstract

The naturally existing chalcogenide Bi 2 Se 3 is topologically nontrivial due to the band inversion caused by the strong spin-orbit coupling inside the bulk of the material. The surface states are spin polarized, protected by the time-inversion symmetry, and thus robust to the scattering caused by nonmagnetic defects. A high-purity topological insulator thin film can be easily grown via molecular beam epitaxy (MBE) on various substrates to enable novel electronics, optics, and spintronics applications. However, the unique surface state properties have historically been limited by the film quality, which is evaluated by crystallinity, surface morphology, and transport data. Here we propose and investigate different MBE growth strategies to improve the quality of Bi 2 Se 3 thin films grown by MBE. Based on the surface passivation status, we have classified the substrates into two categories, self-passivated or unpassivated, and determine the optimal growth mechanisms on the representative sapphire and GaAs, respectively. For Bi 2 Se 3 on GaAs, the surface passivation status determines the dominant growth mechanism. In the end, growths of the topological trivial insulator (Bi 0.5 In 0.5 ) 2 Se 3 (BIS) on GaAs are investigated following the protocols proposed.

Bi2Se3 Growth on (001) GaAs Substrates for Terahertz Integrated Systems

“…The subscripts H, R, and C in this work indicate the hexagonal, rhombohedral, and cubic index systems. (1̅015) H is equivalent to (015) H and (221) R in Bi 2 Se 3 . ,, The Bi 2 Se 3 vdW gaps are oriented parallel to the GaAs(001) C surface for the (0001) H orientation growth and oblique to the surface for the (1̅015) H orientation growth. As shown in Figure c, the (0001) H -oriented [11̅00] H and [1̅21̅0] H Bi 2 Se 3 domains appeared on flatter regions of the GaAs(001) C substrate in the As-desorbed sample, while the (1̅015) H -oriented growth of the [1̅21̅0] H Bi 2 Se 3 domains occurred on a multi-faceted rougher area.…”

“…20−23 Additional work has investigated the growth of Bi 2 Se 3 (0001) H on GaAs(001). 15,24,25 Finally, it has also been demonstrated that Bi 2 Se 3 (1̅ 015) H can be grown on GaAs(001). 14,26 However, these papers generally focused on the overall Bi 2 Se 3 film quality, rather than on understanding and improving the interface between the Bi 2 Se 3 film and the technologically important GaAs(001) substrate.…”

“…TI materials include Bi 2 Se 3 , Bi 2 Te 3 , and Sb 2 Te 3 . Among these materials, Bi 2 Se 3 is widely used as it is relatively easy to synthesize and has a larger band gap than the other TI materials . For these reasons, we chose to use Bi 2 Se 3 as the TI material exemplar in this article.…”

“…Previous work regarding the molecular beam epitaxy (MBE) growth of Bi 2 Se 3 on GaAs and related substrates has been done by a variety of groups. Some of this work has focused on the growth Bi 2 Se 3 (0001) H on GaAs(111) substrates since these substrates have an in-plane hexagonal symmetry similar to that of Bi 2 Se 3 . − Additional work has investigated the growth of Bi 2 Se 3 (0001) H on GaAs(001). ,, Finally, it has also been demonstrated that Bi 2 Se 3 (1̅015) H can be grown on GaAs(001). , However, these papers generally focused on the overall Bi 2 Se 3 film quality, rather than on understanding and improving the interface between the Bi 2 Se 3 film and the technologically important GaAs(001) substrate. A sharp interface is critical to both good film growth and the creation of Bi 2 Se 3 /GaAs­(001) devices.…”

Two‐Dimensional Van Der Waals Topological Materials: Preparation, Properties, and Device Applications

“…Reproduced with permission. [ 173 ] Copyright 2021, American Chemical Society. j) MBE growth process and phase control of 2D MoTe 2 thin film.…”