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Title: Growth of ultrathin Bi 2 Se 3 films by molecular beam epitaxy
[Formula: see text] is a widely studied 3D topological insulator having potential applications in optics, electronics, and spintronics. When the thickness of these films decreases to less than approximately 6 nm, the top and bottom surface states couple, resulting in the opening of a small gap at the Dirac point. In the 2D limit, [Formula: see text] may exhibit quantum spin Hall states. However, growing coalesced ultrathin [Formula: see text] films with a controllable thickness and typical triangular domain morphology in the few nanometer range is challenging. Here, we explore the growth of [Formula: see text] films having thicknesses down to 4 nm on sapphire substrates using molecular beam epitaxy that were then characterized with Hall measurements, atomic force microscopy, and Raman imaging. We find that substrate pretreatment—growing and decomposing a few layers of [Formula: see text] before the actual deposition—is critical to obtaining a completely coalesced film. In addition, higher growth rates and lower substrate temperatures led to improvement in surface roughness, in contrast to what is observed for conventional epitaxy. Overall, coalesced ultrathin [Formula: see text] films with lower surface roughness enable thickness-dependent studies across the transition from a 3D-topological insulator to one with gapped surface states in the 2D regime.  more » « less
Award ID(s):
2011824
PAR ID:
10410512
Author(s) / Creator(s):
; ; ;
Date Published:
Journal Name:
Journal of Vacuum Science & Technology A
Volume:
41
Issue:
1
ISSN:
0734-2101
Page Range / eLocation ID:
012202
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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