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Synthesis and quantum transport properties of Bi₂Se₃ topological insulator nanostructures.

Yan Y, Liao ZM, Zhou YB, Wu HC, Bie YQ, Chen JJ, Meng J, Wu XS, Yu DP - Sci Rep (2013)

Bottom Line: Bi₂Se₃ nanocrystals with various morphologies, including nanotower, nanoplate, nanoflake, nanobeam and nanowire, have been synthesized.Careful analysis of the SdH oscillations suggests the existence of Berry's phase π, which confirms the quantum transport of the surface Dirac fermions in both Bi₂Se₃ nanoplates and nanobeams without intended doping.The observation of the singular quantum transport of the topological surface states implies that the high-quality Bi₂Se₃ nanostructures have superiorities for investigating the novel physical properties and developing the potential applications.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory for Mesoscopic Physics, Department of Physics, Peking University, Beijing 100871, P.R. China.

ABSTRACT
Bi₂Se₃ nanocrystals with various morphologies, including nanotower, nanoplate, nanoflake, nanobeam and nanowire, have been synthesized. Well-distinguished Shubnikov-de Haas (SdH) oscillations were observed in Bi₂Se₃ nanoplates and nanobeams. Careful analysis of the SdH oscillations suggests the existence of Berry's phase π, which confirms the quantum transport of the surface Dirac fermions in both Bi₂Se₃ nanoplates and nanobeams without intended doping. The observation of the singular quantum transport of the topological surface states implies that the high-quality Bi₂Se₃ nanostructures have superiorities for investigating the novel physical properties and developing the potential applications.

No MeSH data available.


Schematic diagram of the growth mechanisms.(a) The crystal structures of Bi2Se3 from side-view (top panel) and top-view (bottom panel). (b) The vapor-liquid-solid growth along [0001] direction. (c) The dominant growth along [10-10] or [01-10] directions. (d) The growth along [11-20] direction and the formation of quasi-one dimensional structure.
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f2: Schematic diagram of the growth mechanisms.(a) The crystal structures of Bi2Se3 from side-view (top panel) and top-view (bottom panel). (b) The vapor-liquid-solid growth along [0001] direction. (c) The dominant growth along [10-10] or [01-10] directions. (d) The growth along [11-20] direction and the formation of quasi-one dimensional structure.

Mentions: The detailed growth mechanisms were presented in Figure 2. Bi2Se3 was layered rhombohedral crystal structure along c axis, as illustrated in Figure 2(a). Here, the c axis [0001] of the hexagonal cell corresponds to Bi2Se3 [111] of the approximately cubic closest-packed layer crystal structure, where five atomic layers in sequence of –Se-Bi-Se-Bi-Se- form a basic unit, i.e. quintuple layer (QL). The interaction within the QLs is strong, but the adjacent QLs are coupled by relatively weak van der Waals interaction. The binding energies are different for different surfaces, which suggests different growth rate along different directions. The catalyst particles serve as nucleation sites for the growth of Bi2Se3 nanostructures. Via slow pumping, the evaporated molecules can be transported by the carrier gas and the dynamic balance during the growth process can also be largely maintained. Under high temperatures, the source vapors have high energy that can overcome the binding energy of [0001] surface, resulting in the growth along c axis with growth rate Vc > Va = Vb (Va, Vb, Vc are the growth rates along a, b, c axis, respectively), as seen the products in Figures 1(a, b) and the sketch in Figure 2(b). Under lower temperatures, the energy of the vapors may be insufficient to overcome the binding energy of [0001] surface. The growth along [10-10] or [01-10] directions becomes dominant and results in the polygon morphologies as shown the products in Figures 1(c–f) and the sketch in Figure 2(c), which are commonly present in epitaxial growth of Bi2Se3 nanoplates412. Under much lower temperatures, the growth induced by catalyst along [11-20] direction breaks the crystal intrinsic symmetry and results in the one-dimensional preferential growth as presented in Figures 1(g, h) and Figure 2(d), respectively. Therefore, different kinds of morphologies of Bi2Se3 nanostructures can be synthesized through changing the distance between the source and the Si substrate which changes the temperature of the collection substrates and energy of the source vapor. Morphologies and good crystallinity of the synthesized samples have been verified by the TEM images, high resolution TEM (HRTEM) images, and SAED patterns, as shown in Figure 3. Furthermore, EDS spectrums (Figures 3(e, f)) collected from the head and the body of one nanobeam (Figure 3(c)) show the Au catalyst particle on the head and the compositions of Bi and Se in the body, which obviously verify the VLS growth mechanism.


Synthesis and quantum transport properties of Bi₂Se₃ topological insulator nanostructures.

Yan Y, Liao ZM, Zhou YB, Wu HC, Bie YQ, Chen JJ, Meng J, Wu XS, Yu DP - Sci Rep (2013)

Schematic diagram of the growth mechanisms.(a) The crystal structures of Bi2Se3 from side-view (top panel) and top-view (bottom panel). (b) The vapor-liquid-solid growth along [0001] direction. (c) The dominant growth along [10-10] or [01-10] directions. (d) The growth along [11-20] direction and the formation of quasi-one dimensional structure.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3569629&req=5

f2: Schematic diagram of the growth mechanisms.(a) The crystal structures of Bi2Se3 from side-view (top panel) and top-view (bottom panel). (b) The vapor-liquid-solid growth along [0001] direction. (c) The dominant growth along [10-10] or [01-10] directions. (d) The growth along [11-20] direction and the formation of quasi-one dimensional structure.
Mentions: The detailed growth mechanisms were presented in Figure 2. Bi2Se3 was layered rhombohedral crystal structure along c axis, as illustrated in Figure 2(a). Here, the c axis [0001] of the hexagonal cell corresponds to Bi2Se3 [111] of the approximately cubic closest-packed layer crystal structure, where five atomic layers in sequence of –Se-Bi-Se-Bi-Se- form a basic unit, i.e. quintuple layer (QL). The interaction within the QLs is strong, but the adjacent QLs are coupled by relatively weak van der Waals interaction. The binding energies are different for different surfaces, which suggests different growth rate along different directions. The catalyst particles serve as nucleation sites for the growth of Bi2Se3 nanostructures. Via slow pumping, the evaporated molecules can be transported by the carrier gas and the dynamic balance during the growth process can also be largely maintained. Under high temperatures, the source vapors have high energy that can overcome the binding energy of [0001] surface, resulting in the growth along c axis with growth rate Vc > Va = Vb (Va, Vb, Vc are the growth rates along a, b, c axis, respectively), as seen the products in Figures 1(a, b) and the sketch in Figure 2(b). Under lower temperatures, the energy of the vapors may be insufficient to overcome the binding energy of [0001] surface. The growth along [10-10] or [01-10] directions becomes dominant and results in the polygon morphologies as shown the products in Figures 1(c–f) and the sketch in Figure 2(c), which are commonly present in epitaxial growth of Bi2Se3 nanoplates412. Under much lower temperatures, the growth induced by catalyst along [11-20] direction breaks the crystal intrinsic symmetry and results in the one-dimensional preferential growth as presented in Figures 1(g, h) and Figure 2(d), respectively. Therefore, different kinds of morphologies of Bi2Se3 nanostructures can be synthesized through changing the distance between the source and the Si substrate which changes the temperature of the collection substrates and energy of the source vapor. Morphologies and good crystallinity of the synthesized samples have been verified by the TEM images, high resolution TEM (HRTEM) images, and SAED patterns, as shown in Figure 3. Furthermore, EDS spectrums (Figures 3(e, f)) collected from the head and the body of one nanobeam (Figure 3(c)) show the Au catalyst particle on the head and the compositions of Bi and Se in the body, which obviously verify the VLS growth mechanism.

Bottom Line: Bi₂Se₃ nanocrystals with various morphologies, including nanotower, nanoplate, nanoflake, nanobeam and nanowire, have been synthesized.Careful analysis of the SdH oscillations suggests the existence of Berry's phase π, which confirms the quantum transport of the surface Dirac fermions in both Bi₂Se₃ nanoplates and nanobeams without intended doping.The observation of the singular quantum transport of the topological surface states implies that the high-quality Bi₂Se₃ nanostructures have superiorities for investigating the novel physical properties and developing the potential applications.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory for Mesoscopic Physics, Department of Physics, Peking University, Beijing 100871, P.R. China.

ABSTRACT
Bi₂Se₃ nanocrystals with various morphologies, including nanotower, nanoplate, nanoflake, nanobeam and nanowire, have been synthesized. Well-distinguished Shubnikov-de Haas (SdH) oscillations were observed in Bi₂Se₃ nanoplates and nanobeams. Careful analysis of the SdH oscillations suggests the existence of Berry's phase π, which confirms the quantum transport of the surface Dirac fermions in both Bi₂Se₃ nanoplates and nanobeams without intended doping. The observation of the singular quantum transport of the topological surface states implies that the high-quality Bi₂Se₃ nanostructures have superiorities for investigating the novel physical properties and developing the potential applications.

No MeSH data available.