A topological insulator composite thin film with high spin-polarized electron channel and its preparation

Abstract

The invention discloses a topological insulator heterogeneous composite film with a high spin polarized electron transport channel, and the topological insulator heterogeneous composite film comprises a 6H-SiC (0001) or SrTiO3 substrate and topological insulator 6QLBi2Se3 and ordinary semiconductor 3QLSb2S3 which are in order grown on the substrate by a molecular beam epitaxy technology in an ultra high vacuum system. Through coverage of the surface of topological insulator Bi2Se3 with the Sb2S3, the electrical properties of the composite film are significantly improved compared with that of a pure Bi2Se3 film; the Dirac point is changed from 0.1eV less than valence-band maximum to 0.09eV higher than valence-band maximum, Fermi velocity is improved from 1.15 eV. Angstrom to 1.61eV. Angstrom, spin polarization rate is also increased from 0.65 to 0.91; at the same time, the width of the spin polarized electron transport channel is improved from about 1nm to 3nm, and can be further expanded according to the needs by increasing of the Sb2S3 covering layer thickness; and the Sb2S3 covering layer can reduce influence on the spin polarized electron flow transport channel due to surface contamination such as oxidation and the like.

Description

technical field [0001] The invention belongs to the field of condensed matter physics, and relates to a topological insulator composite thin film used for spin electronic devices and its preparation. Background technique [0002] Compared with traditional microelectronic devices that rely on the characteristics of electric charges, spintronic devices that use the spin characteristics of electrons have the advantages of high operating speed and low energy consumption. The topological insulator (Topological insulator) discovered in 2006 (Bernevig B.A. et al., Quantum spin Hall effect and topological phase transition in HgTe quantum wells. Science 2006, 314:1757-1761.) is an ideal material for making spintronic devices. This type of material has a highly spin-polarized topological surface state protected by topological symmetry, which can serve as a transport channel for spin-polarized electron flow, and thus can be used to realize the function of spintronic devices ( Pesin D....

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Problems solved by technology

Such as Bi 2 Se 3 The Dirac point of the valence band is at 0.1eV below the top of the valence band, so the working point cannot be set near the Dirac point, otherwise the non-spin-polarized conductive channel in the body will also be opened, and the spin polarizability of the transported electrons will be reduced. , causing resistance and heat loss

Furthermore, near the Dirac point, the energy dispersion is not ideally linear, which reduces the carrier Fermi velocity

(2) If the electronic state far away from the Dirac point is used as the spin current transport channel, the backscattering caused by the distortion of the isoenergy surface will affect the device performance

(Alpichshev Z. et al., STM imaging of electronic waves on the surface of Bi 2 Te 3 :Topologically protected surfacestates and hexagonal warping effects.Phys.Rev.Lett.2010,104:16401-16404.) (3) pure topological insulator film, because its spin current transport channel is limited to the outermost 1QL (quintuple layer, within the range of five atomic layers), so a small amount of contamination on the surface will have a significant impact on the spin current transport channel, thereby degrading the electrical performance of the device

(Kong D. et al., Rapid surface oxidation as a source of surface degradation factor for Bi 2 Se 3 .ACS Nano 2011,5:4698-4703.) (4) Since the spin current channel on the surface of a single topological insulator is confined to a very narrow surface layer, its charge transport capability is also very limited

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