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Temperature-Dependent Site Control of InAs/GaAs (001) Quantum Dots Using a Scanning Tunneling Microscopy Tip During Growth.

Toujyou T, Tsukamoto S - Nanoscale Res Lett (2010)

Bottom Line: However, these dots were remained at least 40 s and collapsed less than 1000 s.Then, we fabricated InAs nano dots (width: 24-150 nm, height: 2.8-28 nm) at 300°C under In and As(4) irradiations.These were not collapsed and considered to high crystalline dots.

View Article: PubMed Central - HTML - PubMed

Affiliation: Center for Collaborative Research, Anan National College of Technology, Anan, Tokushima, 774-0017 Japan.

ABSTRACT
Site-controlled InAs nano dots were successfully fabricated by a STMBE system (in situ scanning tunneling microscopy during molecular beam epitaxy growth) at substrate temperatures from 50 to 430°C. After 1.5 ML of the InAs wetting layer (WL) growth by ordinal Stranski-Krastanov dot fabrication procedures, we applied voltage at particular sites on the InAs WL, creating the site where In atoms, which were migrating on the WL, favored to congregate. At 240°C, InAs nano dots (width: 20-40 nm, height: 1.5-2.0 nm) were fabricated. At 430°C, InAs nano dots (width: 16-20 nm, height: 0.75-1.5 nm) were also fabricated. However, these dots were remained at least 40 s and collapsed less than 1000 s. Then, we fabricated InAs nano dots (width: 24-150 nm, height: 2.8-28 nm) at 300°C under In and As(4) irradiations. These were not collapsed and considered to high crystalline dots.

No MeSH data available.


STMBE images of a dot grown in a hole structure under In and As4 irradiations at 300°C and its line profiles. a Shows the hole structure, b and c were images after supplying additional 0.02 ML and 0.04 ML of InAs, respectively
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Figure 4: STMBE images of a dot grown in a hole structure under In and As4 irradiations at 300°C and its line profiles. a Shows the hole structure, b and c were images after supplying additional 0.02 ML and 0.04 ML of InAs, respectively

Mentions: To prevent the collapse of the dots, we try to fabricate at 300°C. After 1.5 ML of the InAs WL growth at 500°C, we stopped In supply and decreased a substrate temperature to 300°C. We first fabricated a hole structures (width: 25 nm, depth: 3 nm) by applying voltage from −1 to +1 V as shown in Fig. 4a. A tip bias was −0.6 V, a tunnel current was 0.3 nA, and the scan speed was 3,000 nm/s. This hole structure which reached to the GaAs substrate might be considered as the Ga-rich sites compared with other InAs WL region [15]. After fabricating the hole structure, we started supplying In flux again. The amount of InAs supply was estimated at 0.02 ML in every scan. After supplying additional 0.02 ML of InAs, spontaneously, mobile In atoms congregated to this site, forming the dot structure (width: 20 nm, height: 1.7 nm) as shown in Fig. 4b. After further continually supplying of InAs, this dot structure became enlarged (width: 24 nm, height: 2.8 nm), but we could not confirm any other S–K dot structure at this moment (Fig. 4c). After supplying 1.66 ML (1.5 + 0.16 ML) of InAs, S–K dots were fabricated at other place. This indicated the difference of growth rates between the dot structure in the hole structure and the S–K dots. Figure 5 shows the schematic illustration of the fabrication process of a nano dot growth. By applying voltage, a hole structure was artificially created as shown in Fig. 5b, which dug the WL. This hole structure might be considered as the Ga-rich sites compared with other InAs WL region. The migration barrier for In atoms decreases going from GaAs to InAs [9]. This site congregated In atoms, which were mainly migrating on the WL (Fig. 5c), and went easily beyond its critical thickness, forming the dot structure (Fig. 5d).


Temperature-Dependent Site Control of InAs/GaAs (001) Quantum Dots Using a Scanning Tunneling Microscopy Tip During Growth.

Toujyou T, Tsukamoto S - Nanoscale Res Lett (2010)

STMBE images of a dot grown in a hole structure under In and As4 irradiations at 300°C and its line profiles. a Shows the hole structure, b and c were images after supplying additional 0.02 ML and 0.04 ML of InAs, respectively
© Copyright Policy
Related In: Results  -  Collection

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Figure 4: STMBE images of a dot grown in a hole structure under In and As4 irradiations at 300°C and its line profiles. a Shows the hole structure, b and c were images after supplying additional 0.02 ML and 0.04 ML of InAs, respectively
Mentions: To prevent the collapse of the dots, we try to fabricate at 300°C. After 1.5 ML of the InAs WL growth at 500°C, we stopped In supply and decreased a substrate temperature to 300°C. We first fabricated a hole structures (width: 25 nm, depth: 3 nm) by applying voltage from −1 to +1 V as shown in Fig. 4a. A tip bias was −0.6 V, a tunnel current was 0.3 nA, and the scan speed was 3,000 nm/s. This hole structure which reached to the GaAs substrate might be considered as the Ga-rich sites compared with other InAs WL region [15]. After fabricating the hole structure, we started supplying In flux again. The amount of InAs supply was estimated at 0.02 ML in every scan. After supplying additional 0.02 ML of InAs, spontaneously, mobile In atoms congregated to this site, forming the dot structure (width: 20 nm, height: 1.7 nm) as shown in Fig. 4b. After further continually supplying of InAs, this dot structure became enlarged (width: 24 nm, height: 2.8 nm), but we could not confirm any other S–K dot structure at this moment (Fig. 4c). After supplying 1.66 ML (1.5 + 0.16 ML) of InAs, S–K dots were fabricated at other place. This indicated the difference of growth rates between the dot structure in the hole structure and the S–K dots. Figure 5 shows the schematic illustration of the fabrication process of a nano dot growth. By applying voltage, a hole structure was artificially created as shown in Fig. 5b, which dug the WL. This hole structure might be considered as the Ga-rich sites compared with other InAs WL region. The migration barrier for In atoms decreases going from GaAs to InAs [9]. This site congregated In atoms, which were mainly migrating on the WL (Fig. 5c), and went easily beyond its critical thickness, forming the dot structure (Fig. 5d).

Bottom Line: However, these dots were remained at least 40 s and collapsed less than 1000 s.Then, we fabricated InAs nano dots (width: 24-150 nm, height: 2.8-28 nm) at 300°C under In and As(4) irradiations.These were not collapsed and considered to high crystalline dots.

View Article: PubMed Central - HTML - PubMed

Affiliation: Center for Collaborative Research, Anan National College of Technology, Anan, Tokushima, 774-0017 Japan.

ABSTRACT
Site-controlled InAs nano dots were successfully fabricated by a STMBE system (in situ scanning tunneling microscopy during molecular beam epitaxy growth) at substrate temperatures from 50 to 430°C. After 1.5 ML of the InAs wetting layer (WL) growth by ordinal Stranski-Krastanov dot fabrication procedures, we applied voltage at particular sites on the InAs WL, creating the site where In atoms, which were migrating on the WL, favored to congregate. At 240°C, InAs nano dots (width: 20-40 nm, height: 1.5-2.0 nm) were fabricated. At 430°C, InAs nano dots (width: 16-20 nm, height: 0.75-1.5 nm) were also fabricated. However, these dots were remained at least 40 s and collapsed less than 1000 s. Then, we fabricated InAs nano dots (width: 24-150 nm, height: 2.8-28 nm) at 300°C under In and As(4) irradiations. These were not collapsed and considered to high crystalline dots.

No MeSH data available.