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Simple two-step fabrication method of Bi2Te3 nanowires.

Kang J, Noh JS, Lee W - Nanoscale Res Lett (2011)

Bottom Line: Its performance is expected to be greatly improved when the material takes nanowire structures.However, it is very difficult to grow high-quality Bi2Te3 nanowires.Transmission electron microscopy study shows that Bi2Te3 nanowires grown by our technique are highly single-crystalline and oriented along [110] direction.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Materials Science and Engineering, Yonsei University, 262 Seongsanno, Seodaemun-gu, Seoul 120-749, Korea. wooyoung@yonsei.ac.kr.

ABSTRACT
Bismuth telluride (Bi2Te3) is an attractive material for both thermoelectric and topological insulator applications. Its performance is expected to be greatly improved when the material takes nanowire structures. However, it is very difficult to grow high-quality Bi2Te3 nanowires. In this study, a simple and reliable method for the growth of Bi2Te3 nanowires is reported, which uses post-sputtering and annealing in combination with the conventional method involving on-film formation of nanowires. Transmission electron microscopy study shows that Bi2Te3 nanowires grown by our technique are highly single-crystalline and oriented along [110] direction.

No MeSH data available.


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A cross section of a Bi2Te3 nanowire. (a) Pt is deposited locally to protect Bi2Te3 nanowire during the dual beam FIB process. (b) A SEM image shows the cross section of Bi2Te3 nanowire. (c) A low-magnification TEM image of the cross section of Bi2Te3 nanowire. There is no interface between the original Bi core and the Bi2Te3 shell after annealing. A SAED pattern and a HR-TEM image reveal that Bi2Te3 nanowire is highly single-crystalline across the nanowire.
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Figure 4: A cross section of a Bi2Te3 nanowire. (a) Pt is deposited locally to protect Bi2Te3 nanowire during the dual beam FIB process. (b) A SEM image shows the cross section of Bi2Te3 nanowire. (c) A low-magnification TEM image of the cross section of Bi2Te3 nanowire. There is no interface between the original Bi core and the Bi2Te3 shell after annealing. A SAED pattern and a HR-TEM image reveal that Bi2Te3 nanowire is highly single-crystalline across the nanowire.

Mentions: Because our method for Bi2Te3 nanowires synthesis uses heterogeneous nanowire structures consisting of OFF-ON-grown Bi core and post-deposited Bi2Te3 shell, the homogeneity of final nanowires should be verified. The biggest concern may be a residual existence of an interface between the original core and the shell layers. To examine this possibility, cross-sectional TEM measurements of thin slices randomly taken from the nanowires were carried out. For the TEM sampling, dual-beam focused ion beam (FIB) was utilized based on the process depicted in Figure 4. Pt was deposited onto a Bi2Te3 nanowire to prevent any distortion during the dual-beam FIB processes (Figure 4a). Focused gallium (Ga) ion beam or electron beam generated from a fine nozzle makes it possible to deposit or etch a Pt film area selectively on the substrate. The Ga ion beam dissociates injected Pt-precursor molecules and removes the ligands from them on the selective area, resulting in local deposition of the Pt film. This is the well-known technique for TEM sampling [19]. Then, the Omni-probe of the dual-beam FIB tool took the etched TEM sample with a thickness of below 100 nm away from the SiO2/Si substrate. The final sample for TEM measurement is shown in Figure 4b. Figure 4c is the cross-sectional TEM image of a Bi2Te3 nanowire. From a HR-TEM image and SAED pattern of the part where a Bi core-Bi2Te3 shell interface was originally located, it is found that the synthesized Bi2Te3 nanowire has no interface inside and is crystalline across the cross section. These results indicate that the inter-diffusion of component atoms actively occurs between the Bi core and the Bi2Te3 shell during a 10-h annealing at the elevated temperature, with evaporation of excess Bi atoms at the nanowire surface.


Simple two-step fabrication method of Bi2Te3 nanowires.

Kang J, Noh JS, Lee W - Nanoscale Res Lett (2011)

A cross section of a Bi2Te3 nanowire. (a) Pt is deposited locally to protect Bi2Te3 nanowire during the dual beam FIB process. (b) A SEM image shows the cross section of Bi2Te3 nanowire. (c) A low-magnification TEM image of the cross section of Bi2Te3 nanowire. There is no interface between the original Bi core and the Bi2Te3 shell after annealing. A SAED pattern and a HR-TEM image reveal that Bi2Te3 nanowire is highly single-crystalline across the nanowire.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3211341&req=5

Figure 4: A cross section of a Bi2Te3 nanowire. (a) Pt is deposited locally to protect Bi2Te3 nanowire during the dual beam FIB process. (b) A SEM image shows the cross section of Bi2Te3 nanowire. (c) A low-magnification TEM image of the cross section of Bi2Te3 nanowire. There is no interface between the original Bi core and the Bi2Te3 shell after annealing. A SAED pattern and a HR-TEM image reveal that Bi2Te3 nanowire is highly single-crystalline across the nanowire.
Mentions: Because our method for Bi2Te3 nanowires synthesis uses heterogeneous nanowire structures consisting of OFF-ON-grown Bi core and post-deposited Bi2Te3 shell, the homogeneity of final nanowires should be verified. The biggest concern may be a residual existence of an interface between the original core and the shell layers. To examine this possibility, cross-sectional TEM measurements of thin slices randomly taken from the nanowires were carried out. For the TEM sampling, dual-beam focused ion beam (FIB) was utilized based on the process depicted in Figure 4. Pt was deposited onto a Bi2Te3 nanowire to prevent any distortion during the dual-beam FIB processes (Figure 4a). Focused gallium (Ga) ion beam or electron beam generated from a fine nozzle makes it possible to deposit or etch a Pt film area selectively on the substrate. The Ga ion beam dissociates injected Pt-precursor molecules and removes the ligands from them on the selective area, resulting in local deposition of the Pt film. This is the well-known technique for TEM sampling [19]. Then, the Omni-probe of the dual-beam FIB tool took the etched TEM sample with a thickness of below 100 nm away from the SiO2/Si substrate. The final sample for TEM measurement is shown in Figure 4b. Figure 4c is the cross-sectional TEM image of a Bi2Te3 nanowire. From a HR-TEM image and SAED pattern of the part where a Bi core-Bi2Te3 shell interface was originally located, it is found that the synthesized Bi2Te3 nanowire has no interface inside and is crystalline across the cross section. These results indicate that the inter-diffusion of component atoms actively occurs between the Bi core and the Bi2Te3 shell during a 10-h annealing at the elevated temperature, with evaporation of excess Bi atoms at the nanowire surface.

Bottom Line: Its performance is expected to be greatly improved when the material takes nanowire structures.However, it is very difficult to grow high-quality Bi2Te3 nanowires.Transmission electron microscopy study shows that Bi2Te3 nanowires grown by our technique are highly single-crystalline and oriented along [110] direction.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Materials Science and Engineering, Yonsei University, 262 Seongsanno, Seodaemun-gu, Seoul 120-749, Korea. wooyoung@yonsei.ac.kr.

ABSTRACT
Bismuth telluride (Bi2Te3) is an attractive material for both thermoelectric and topological insulator applications. Its performance is expected to be greatly improved when the material takes nanowire structures. However, it is very difficult to grow high-quality Bi2Te3 nanowires. In this study, a simple and reliable method for the growth of Bi2Te3 nanowires is reported, which uses post-sputtering and annealing in combination with the conventional method involving on-film formation of nanowires. Transmission electron microscopy study shows that Bi2Te3 nanowires grown by our technique are highly single-crystalline and oriented along [110] direction.

No MeSH data available.


Related in: MedlinePlus