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Intrinsic topological insulator Bi(1.5)Sb(0.5)Te(3-x)Se(x) thin crystals.

Wang W, Li L, Zou W, He L, Song F, Zhang R, Wu X, Zhang F - Sci Rep (2015)

Bottom Line: A correlation between the structure and the physical properties has been revealed.We found out that within the rhombohedral structure, the composition with most Te substituting Se has the highest resistivity.On the other hand, segregation of other composition phases will introduce much higher bulk concentration.

View Article: PubMed Central - PubMed

Affiliation: National Laboratory of Solid State Microstructures, Center of Photovoltaic Engineering and School of Physics, Nanjing University, Nanjing 210093, China.

ABSTRACT
The quaternary topological insulator (Bi,Sb)2(Te,Se)3 has demonstrated topological surface states with an insulating bulk. Scientists have identified an optimized composition of Bi(1.5)Sb(0.5)Te(1.7)Se(1.3) with the highest resistivity reported. But the physics that drive to this composition remains unclear. Here we report the crystal structure and the magneto-transport properties of Bi(1.5)Sb(0.5)Te(3-x)Se(x) (BSTS) series. A correlation between the structure and the physical properties has been revealed. We found out that within the rhombohedral structure, the composition with most Te substituting Se has the highest resistivity. On the other hand, segregation of other composition phases will introduce much higher bulk concentration.

No MeSH data available.


Related in: MedlinePlus

(a) Temperature dependences of the low field (1T) Hall coefficient RH for varies Se concentration x.Positive RH has been observed above 100 K for x = 1.2. (b) The value of RH at 1.9 K as a function of Se concentration x. The largest /RH/ can be observed at x = 1.2, corresponding a 2D carries density of 1.08 × 10−13 cm−2. c) Magnetic field dependent Hall conductance Gxy for Bi1.5Sb0.5Te1.8Se1.2 (x = 1.2) at 100 K. The black line is a three band model fitting. The brown, green and blue dashed lines represent bulk, surface and impurity channels, respectively.
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f3: (a) Temperature dependences of the low field (1T) Hall coefficient RH for varies Se concentration x.Positive RH has been observed above 100 K for x = 1.2. (b) The value of RH at 1.9 K as a function of Se concentration x. The largest /RH/ can be observed at x = 1.2, corresponding a 2D carries density of 1.08 × 10−13 cm−2. c) Magnetic field dependent Hall conductance Gxy for Bi1.5Sb0.5Te1.8Se1.2 (x = 1.2) at 100 K. The black line is a three band model fitting. The brown, green and blue dashed lines represent bulk, surface and impurity channels, respectively.

Mentions: To further understand the transport properties, we have performed the Hall measurement. Figure 3a shows the temperature dependence of the low-field (1T) Hall coefficient RH, for all the samples. The RH in Bi1.5Sb0.5Te1.8Se1.2, shows a crossing from positive to negative at 100 K. Considering the activation behavior at high temperature, this can be understood as the electrons from bulk valence band excited to the impurity band leaving the bulk holes dominate conducting81316, at high temperatures. At low temperatures, the excited bulk electrons freeze back to the bulk valence band, leaving electrons in the impurity band and surface states dominate the conductance. Thus the majority carrier type changes back to electrons, although both electrons and holes co-exist in the system, the observed carrier type change is due to the competition between them, which have been observed many times in similar highly compensated systems812.


Intrinsic topological insulator Bi(1.5)Sb(0.5)Te(3-x)Se(x) thin crystals.

Wang W, Li L, Zou W, He L, Song F, Zhang R, Wu X, Zhang F - Sci Rep (2015)

(a) Temperature dependences of the low field (1T) Hall coefficient RH for varies Se concentration x.Positive RH has been observed above 100 K for x = 1.2. (b) The value of RH at 1.9 K as a function of Se concentration x. The largest /RH/ can be observed at x = 1.2, corresponding a 2D carries density of 1.08 × 10−13 cm−2. c) Magnetic field dependent Hall conductance Gxy for Bi1.5Sb0.5Te1.8Se1.2 (x = 1.2) at 100 K. The black line is a three band model fitting. The brown, green and blue dashed lines represent bulk, surface and impurity channels, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4300459&req=5

f3: (a) Temperature dependences of the low field (1T) Hall coefficient RH for varies Se concentration x.Positive RH has been observed above 100 K for x = 1.2. (b) The value of RH at 1.9 K as a function of Se concentration x. The largest /RH/ can be observed at x = 1.2, corresponding a 2D carries density of 1.08 × 10−13 cm−2. c) Magnetic field dependent Hall conductance Gxy for Bi1.5Sb0.5Te1.8Se1.2 (x = 1.2) at 100 K. The black line is a three band model fitting. The brown, green and blue dashed lines represent bulk, surface and impurity channels, respectively.
Mentions: To further understand the transport properties, we have performed the Hall measurement. Figure 3a shows the temperature dependence of the low-field (1T) Hall coefficient RH, for all the samples. The RH in Bi1.5Sb0.5Te1.8Se1.2, shows a crossing from positive to negative at 100 K. Considering the activation behavior at high temperature, this can be understood as the electrons from bulk valence band excited to the impurity band leaving the bulk holes dominate conducting81316, at high temperatures. At low temperatures, the excited bulk electrons freeze back to the bulk valence band, leaving electrons in the impurity band and surface states dominate the conductance. Thus the majority carrier type changes back to electrons, although both electrons and holes co-exist in the system, the observed carrier type change is due to the competition between them, which have been observed many times in similar highly compensated systems812.

Bottom Line: A correlation between the structure and the physical properties has been revealed.We found out that within the rhombohedral structure, the composition with most Te substituting Se has the highest resistivity.On the other hand, segregation of other composition phases will introduce much higher bulk concentration.

View Article: PubMed Central - PubMed

Affiliation: National Laboratory of Solid State Microstructures, Center of Photovoltaic Engineering and School of Physics, Nanjing University, Nanjing 210093, China.

ABSTRACT
The quaternary topological insulator (Bi,Sb)2(Te,Se)3 has demonstrated topological surface states with an insulating bulk. Scientists have identified an optimized composition of Bi(1.5)Sb(0.5)Te(1.7)Se(1.3) with the highest resistivity reported. But the physics that drive to this composition remains unclear. Here we report the crystal structure and the magneto-transport properties of Bi(1.5)Sb(0.5)Te(3-x)Se(x) (BSTS) series. A correlation between the structure and the physical properties has been revealed. We found out that within the rhombohedral structure, the composition with most Te substituting Se has the highest resistivity. On the other hand, segregation of other composition phases will introduce much higher bulk concentration.

No MeSH data available.


Related in: MedlinePlus