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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.


(a) The image of the as-grown bulk crystal, sample size is about 10 mm × 7 mm. Inset shows the optical image of the Hall bar device. (b) Selected area electron diffraction patterns of Bi1.5Sb0.5Te3-xSex samples. Six-fold symmetry is present for x = 1.3 sample. (c) XRD patterns for a series of Bi1.5Sb0.5Te3-xSex samples. The data have been shifted by one order of magnitude each for clarity. All major diffraction peaks can be indexed as the (003) family. A systematic shift to the left can be observed as Se concentration x decreases. Additional small peaks, indicated by arrows, exist for x below 1.2 samples. Those peaks can be identified as diffraction peaks coming from Sb2Te2Se and Sb2Te3, demonstrating the presence of phase segregation. (d) (red line) The out-of-plane lattice constant c, calculated from the majority peaks, demonstrate a monotonic increases as Se concentration decreases. (blue line) The height of Sb2Te3 (0 1 11) peak vs Se concentration x clearly shows that it emerges below x = 1.2.
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f1: (a) The image of the as-grown bulk crystal, sample size is about 10 mm × 7 mm. Inset shows the optical image of the Hall bar device. (b) Selected area electron diffraction patterns of Bi1.5Sb0.5Te3-xSex samples. Six-fold symmetry is present for x = 1.3 sample. (c) XRD patterns for a series of Bi1.5Sb0.5Te3-xSex samples. The data have been shifted by one order of magnitude each for clarity. All major diffraction peaks can be indexed as the (003) family. A systematic shift to the left can be observed as Se concentration x decreases. Additional small peaks, indicated by arrows, exist for x below 1.2 samples. Those peaks can be identified as diffraction peaks coming from Sb2Te2Se and Sb2Te3, demonstrating the presence of phase segregation. (d) (red line) The out-of-plane lattice constant c, calculated from the majority peaks, demonstrate a monotonic increases as Se concentration decreases. (blue line) The height of Sb2Te3 (0 1 11) peak vs Se concentration x clearly shows that it emerges below x = 1.2.

Mentions: The single crystals of Bi1.5Sb0.5Te3-xSex were grown by modified Bridgman method, details can be found in the method section. The resulting crystals can be easily cleaved along the (111) plane with a shiny surface, as shown in Figure 1a. Transmission electron microscopy (TEM) was performed to determine the structural characteristics. Flakes of the Bi1.5Sb0.5Te3-xSex (BSTS) were obtained by mechanical exfoliation of cleaved crystals. Selected-area electron diffraction (SAED) patterns for x = 1.2 to 1.5 samples indicate the perfect single crystalline rhombohedral phase13 with a six-fold symmetry, as shown in Figure 1b right. On the other hand, for the x = 1.1 sample, Bi1.5Sb0.5Te1.9Se1.1, the relatively even peak intensity suggested a random mixed hexagonal structure. This demonstrates a transition taken in place as Se concentration decreased from x = 1.2 to 1.1.


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) The image of the as-grown bulk crystal, sample size is about 10 mm × 7 mm. Inset shows the optical image of the Hall bar device. (b) Selected area electron diffraction patterns of Bi1.5Sb0.5Te3-xSex samples. Six-fold symmetry is present for x = 1.3 sample. (c) XRD patterns for a series of Bi1.5Sb0.5Te3-xSex samples. The data have been shifted by one order of magnitude each for clarity. All major diffraction peaks can be indexed as the (003) family. A systematic shift to the left can be observed as Se concentration x decreases. Additional small peaks, indicated by arrows, exist for x below 1.2 samples. Those peaks can be identified as diffraction peaks coming from Sb2Te2Se and Sb2Te3, demonstrating the presence of phase segregation. (d) (red line) The out-of-plane lattice constant c, calculated from the majority peaks, demonstrate a monotonic increases as Se concentration decreases. (blue line) The height of Sb2Te3 (0 1 11) peak vs Se concentration x clearly shows that it emerges below x = 1.2.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: (a) The image of the as-grown bulk crystal, sample size is about 10 mm × 7 mm. Inset shows the optical image of the Hall bar device. (b) Selected area electron diffraction patterns of Bi1.5Sb0.5Te3-xSex samples. Six-fold symmetry is present for x = 1.3 sample. (c) XRD patterns for a series of Bi1.5Sb0.5Te3-xSex samples. The data have been shifted by one order of magnitude each for clarity. All major diffraction peaks can be indexed as the (003) family. A systematic shift to the left can be observed as Se concentration x decreases. Additional small peaks, indicated by arrows, exist for x below 1.2 samples. Those peaks can be identified as diffraction peaks coming from Sb2Te2Se and Sb2Te3, demonstrating the presence of phase segregation. (d) (red line) The out-of-plane lattice constant c, calculated from the majority peaks, demonstrate a monotonic increases as Se concentration decreases. (blue line) The height of Sb2Te3 (0 1 11) peak vs Se concentration x clearly shows that it emerges below x = 1.2.
Mentions: The single crystals of Bi1.5Sb0.5Te3-xSex were grown by modified Bridgman method, details can be found in the method section. The resulting crystals can be easily cleaved along the (111) plane with a shiny surface, as shown in Figure 1a. Transmission electron microscopy (TEM) was performed to determine the structural characteristics. Flakes of the Bi1.5Sb0.5Te3-xSex (BSTS) were obtained by mechanical exfoliation of cleaved crystals. Selected-area electron diffraction (SAED) patterns for x = 1.2 to 1.5 samples indicate the perfect single crystalline rhombohedral phase13 with a six-fold symmetry, as shown in Figure 1b right. On the other hand, for the x = 1.1 sample, Bi1.5Sb0.5Te1.9Se1.1, the relatively even peak intensity suggested a random mixed hexagonal structure. This demonstrates a transition taken in place as Se concentration decreased from x = 1.2 to 1.1.

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.