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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.


Schematic representation of Bi2Te3 nanowire synthesis method. Step 1: Bi nanowires are grown on the oxidized Si substrate by the OFF-ON method. Step 2: Bi2Te3 is deposited onto the substrate containing the Bi nanowires by in situ RF sputtering, which forms Bi-Bi2Te3 core/shell nanowires. Homogeneous Bi2Te3 nanowires are synthesized during the vacuum annealing at 350°C.
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Figure 1: Schematic representation of Bi2Te3 nanowire synthesis method. Step 1: Bi nanowires are grown on the oxidized Si substrate by the OFF-ON method. Step 2: Bi2Te3 is deposited onto the substrate containing the Bi nanowires by in situ RF sputtering, which forms Bi-Bi2Te3 core/shell nanowires. Homogeneous Bi2Te3 nanowires are synthesized during the vacuum annealing at 350°C.

Mentions: Figure 1 illustrates the schematics of Bi2Te3 nanowires synthesis process based on the OFF-ON method. To synthesize Bi2Te3 nanowires, Bi nanowires are grown by the OFF-ON method in the first step [17]. For Bi nanowire growth, a Bi thin film is first deposited onto a SiO2/Si substrate at a rate of 32.7 Å/s by radio frequency (RF) sputtering under a base pressure of 10-7 Torr. Then, the Bi film on the SiO2/Si substrate is thermally annealed at 250°C for 10 h in an ultrahigh vacuum to grow Bi nanowires. Bi nanowires spontaneously grow to release the compressive stress acting on the Bi film, which is produced by the large thermal expansion coefficient difference between a Bi thin film (13.4 × 10-6/°C) and a SiO2/Si substrate ((0.5 × 10-6/°C)/(2.4 × 10-6/°C)) [17]. After the Bi nanowire growth is completed, a Bi2Te3 thin film is deposited onto the Bi nanowire-including SiO2/Si substrate using in situ RF sputtering under a base pressure of 10-7 Torr. The samples then undergo vacuum annealing at 350°C for 10 h. During this second step, Bi2Te3 nanowires are synthesized, as the component atoms are inter-diffused between the Bi core nanowire and the Bi2Te3 surface layer. Moreover, the excess Bi atoms evaporate due to the high annealing temperature (350°C) well above the melting point of Bi (271.5°C), leaving behind stoichiometric Bi2Te3 nanowires. The probability of Te evaporation is expected to be low, since the annealing temperature (350°C) is significantly lower than the melting points of Te (449.5°C) and Bi2Te3 (585°C). The whole process is very simple, as schematically depicted in Figure 1. To characterize Bi2Te3 nanowires in detail, atomic structure, crystalline quality, and composition are analyzed using high-resolution transmission electron microscopy (HR-TEM).


Simple two-step fabrication method of Bi2Te3 nanowires.

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

Schematic representation of Bi2Te3 nanowire synthesis method. Step 1: Bi nanowires are grown on the oxidized Si substrate by the OFF-ON method. Step 2: Bi2Te3 is deposited onto the substrate containing the Bi nanowires by in situ RF sputtering, which forms Bi-Bi2Te3 core/shell nanowires. Homogeneous Bi2Te3 nanowires are synthesized during the vacuum annealing at 350°C.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211341&req=5

Figure 1: Schematic representation of Bi2Te3 nanowire synthesis method. Step 1: Bi nanowires are grown on the oxidized Si substrate by the OFF-ON method. Step 2: Bi2Te3 is deposited onto the substrate containing the Bi nanowires by in situ RF sputtering, which forms Bi-Bi2Te3 core/shell nanowires. Homogeneous Bi2Te3 nanowires are synthesized during the vacuum annealing at 350°C.
Mentions: Figure 1 illustrates the schematics of Bi2Te3 nanowires synthesis process based on the OFF-ON method. To synthesize Bi2Te3 nanowires, Bi nanowires are grown by the OFF-ON method in the first step [17]. For Bi nanowire growth, a Bi thin film is first deposited onto a SiO2/Si substrate at a rate of 32.7 Å/s by radio frequency (RF) sputtering under a base pressure of 10-7 Torr. Then, the Bi film on the SiO2/Si substrate is thermally annealed at 250°C for 10 h in an ultrahigh vacuum to grow Bi nanowires. Bi nanowires spontaneously grow to release the compressive stress acting on the Bi film, which is produced by the large thermal expansion coefficient difference between a Bi thin film (13.4 × 10-6/°C) and a SiO2/Si substrate ((0.5 × 10-6/°C)/(2.4 × 10-6/°C)) [17]. After the Bi nanowire growth is completed, a Bi2Te3 thin film is deposited onto the Bi nanowire-including SiO2/Si substrate using in situ RF sputtering under a base pressure of 10-7 Torr. The samples then undergo vacuum annealing at 350°C for 10 h. During this second step, Bi2Te3 nanowires are synthesized, as the component atoms are inter-diffused between the Bi core nanowire and the Bi2Te3 surface layer. Moreover, the excess Bi atoms evaporate due to the high annealing temperature (350°C) well above the melting point of Bi (271.5°C), leaving behind stoichiometric Bi2Te3 nanowires. The probability of Te evaporation is expected to be low, since the annealing temperature (350°C) is significantly lower than the melting points of Te (449.5°C) and Bi2Te3 (585°C). The whole process is very simple, as schematically depicted in Figure 1. To characterize Bi2Te3 nanowires in detail, atomic structure, crystalline quality, and composition are analyzed using high-resolution transmission electron microscopy (HR-TEM).

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.