Abstract
We report the growth of self-assembled Bi2Se3 quantum dots (QDs) by molecular beam epitaxy on GaAs substrates using the droplet epitaxy technique. The QD formation occurs after anneal of Bismuth droplets under Selenium flux. Characterization by atomic force microscopy, scanning electron microscopy, X-ray diffraction, high-resolution transmission electron microscopy and X-ray reflectance spectroscopy is presented. Raman spectra confirm the QD quality. The quantum dots are crystalline, with hexagonal shape, and have average dimensions of 12-nm height (12 quintuple layers) and 46-nm width, and a density of 8.5 × 109 cm−2. This droplet growth technique provides a means to produce topological insulator QDs in a reproducible and controllable way, providing convenient access to a promising quantum material with singular spin properties.
Highlights
The electronic confinement in all three dimensions of semiconductor quantum dots (QDs) leads to unique quantum properties
In this work we demonstrate a viable method to create self-assembled quantum dots of Bi2Se3 by molecular beam epitaxy based on the droplet epitaxy technique
The samples were grown in a dual-chamber Riber 2300P system equipped with in situ reflection high-energy electron diffraction (RHEED)
Summary
The electronic confinement in all three dimensions of semiconductor quantum dots (QDs) leads to unique quantum properties. A discrete energy spectrum is produced, and the confinement impacts how the electrons interact with each other and to external influences, such as electric and magnetic fields These quantum effects can be tuned by changes in the sizes of the dots or the strength of the confining potential. Three-dimensional TIs, such as Bi2Se3 and related materials, are insulators in the bulk form, usually with a narrow band gap They have surface states with spins that are locked with momentum and protected by time-reversal symmetry[12]. Among the many TIs, Bi2Se3 is interesting because its band gap is larger than those of most other TIs, and the experimentally verified Dirac cone is at the gamma point[13] These materials exhibit a tetradymite crystal structure with Se-Bi-Se-Bi-Se units, commonly referred to as quintuple layers, that are bonded together by van der Waals forces[14]. In this work we demonstrate a viable method to create self-assembled quantum dots of Bi2Se3 by molecular beam epitaxy based on the droplet epitaxy technique
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