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Fabrication of self-assembled Au droplets by the systematic variation of the deposition amount on various type-B GaAs surfaces.

Sui M, Li MY, Kim ES, Lee J - Nanoscale Res Lett (2014)

Bottom Line: Under an identical growth condition, the self-assembled Au droplets of mini to supersizes are successfully synthesized via the Volmer-Weber growth mode.Depending on the DA, an apparent evolution is clearly observed in terms of the average height (AH), lateral diameter (LD), and average density (AD).In addition, accompanied with the dimensional expansion, the AD of Au droplets drastically swings on 2 orders of magnitudes from 3.2 × 10(10) to 4.2 × 10(8) cm(-2).

View Article: PubMed Central - HTML - PubMed

Affiliation: College of Electronics and Information, Kwangwoon University, Nowon-gu Seoul 139-701, South Korea.

ABSTRACT
The fabrication of self-assembled Au droplets is successfully demonstrated on various GaAs (n11)B, where n is 2, 4, 5, 7, 8, and 9, by the systematic variation of the Au deposition amount (DA) from 2 to 12 nm with subsequent annealing at 550°C. Under an identical growth condition, the self-assembled Au droplets of mini to supersizes are successfully synthesized via the Volmer-Weber growth mode. Depending on the DA, an apparent evolution is clearly observed in terms of the average height (AH), lateral diameter (LD), and average density (AD). For example, compared with the mini Au droplets with a DA of 2 nm, AH of 22.5 nm, and LD of 86.5 nm, the super Au droplets with 12-nm DA show significantly increased AH of 316% and LD of 320%, reaching an AH of 71.1 nm and LD of 276.8 nm on GaAs (211)B. In addition, accompanied with the dimensional expansion, the AD of Au droplets drastically swings on 2 orders of magnitudes from 3.2 × 10(10) to 4.2 × 10(8) cm(-2). The results are systematically analyzed with respect to the atomic force microscopy (AFM) and scanning electron microscopy (SEM) images, energy-dispersive X-ray spectrometry (EDS) spectra, cross-sectional line profiles, Fourier filter transform (FFT) power spectra, and root-mean-square (RMS) roughness as well as the droplet dimension and density summary, respectively.

No MeSH data available.


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Au droplet evolution as a function of the DA. (a-x) Self-assembled Au droplets fabricated by the variation of the Au deposition amount on GaAs (411)B, (711)B, (811)B, and (911)B. The resulting droplets are presented with AFM top views of 1 × 1 μm2.
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Figure 9: Au droplet evolution as a function of the DA. (a-x) Self-assembled Au droplets fabricated by the variation of the Au deposition amount on GaAs (411)B, (711)B, (811)B, and (911)B. The resulting droplets are presented with AFM top views of 1 × 1 μm2.

Mentions: Figure 9 shows the Au droplet evolution as a function of the DA along with the systematic annealing at 550°C on GaAs (411)B, (711)B, (811)B, and (911)B, respectively. As summarized in Table 2, the results in terms of the size and density evolution are quite analogous to the previous two surfaces. For instance, the size of Au droplets on GaAs (411)B was gradually increased (by × 3.16 for AH and × 3.20 for LD), while the AD was progressively decreased by nearly 2 orders during the variation of the DAs from 2 to 12 nm as clearly shown in Table 2. Similar trends of Au droplet evolution on the other three surfaces can be clearly seen in Figure 9 with the comparable magnitude of changes. In general, various GaAs (n11)B show distinction in terms of the atom density, dangling bonds, and step density [29-31], and as a result, the resulting self-assembled nanostructures can show different behaviors in terms of size and density and even configurations. However, in this experiment, the difference in the result appeared to be minor. Perhaps, it is because the diffusion length of adatoms has a much stronger dependency on the activation energy and substrate temperature. As mentioned, the diffusion length increases by the square root of the product of the diffusion coefficient and residual time of adatoms (), and the diffusion coefficient is strongly proportional to the substrate temperature (D ∝ Tsub). In this experiment, the substrate temperature was fixed at 550°C, and thus the size of the Au droplets can be increased by absorbing Au adatoms within the diffusion length as discussed. Likewise, the diffusion length can also be affected by the variation of atom density, dangling bonds, and step density. However, the difference or the effect induced by the variation of the index to the surface diffusion seems to be relatively smaller as compared to that induced by the substrate temperature [35].


Fabrication of self-assembled Au droplets by the systematic variation of the deposition amount on various type-B GaAs surfaces.

Sui M, Li MY, Kim ES, Lee J - Nanoscale Res Lett (2014)

Au droplet evolution as a function of the DA. (a-x) Self-assembled Au droplets fabricated by the variation of the Au deposition amount on GaAs (411)B, (711)B, (811)B, and (911)B. The resulting droplets are presented with AFM top views of 1 × 1 μm2.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4150864&req=5

Figure 9: Au droplet evolution as a function of the DA. (a-x) Self-assembled Au droplets fabricated by the variation of the Au deposition amount on GaAs (411)B, (711)B, (811)B, and (911)B. The resulting droplets are presented with AFM top views of 1 × 1 μm2.
Mentions: Figure 9 shows the Au droplet evolution as a function of the DA along with the systematic annealing at 550°C on GaAs (411)B, (711)B, (811)B, and (911)B, respectively. As summarized in Table 2, the results in terms of the size and density evolution are quite analogous to the previous two surfaces. For instance, the size of Au droplets on GaAs (411)B was gradually increased (by × 3.16 for AH and × 3.20 for LD), while the AD was progressively decreased by nearly 2 orders during the variation of the DAs from 2 to 12 nm as clearly shown in Table 2. Similar trends of Au droplet evolution on the other three surfaces can be clearly seen in Figure 9 with the comparable magnitude of changes. In general, various GaAs (n11)B show distinction in terms of the atom density, dangling bonds, and step density [29-31], and as a result, the resulting self-assembled nanostructures can show different behaviors in terms of size and density and even configurations. However, in this experiment, the difference in the result appeared to be minor. Perhaps, it is because the diffusion length of adatoms has a much stronger dependency on the activation energy and substrate temperature. As mentioned, the diffusion length increases by the square root of the product of the diffusion coefficient and residual time of adatoms (), and the diffusion coefficient is strongly proportional to the substrate temperature (D ∝ Tsub). In this experiment, the substrate temperature was fixed at 550°C, and thus the size of the Au droplets can be increased by absorbing Au adatoms within the diffusion length as discussed. Likewise, the diffusion length can also be affected by the variation of atom density, dangling bonds, and step density. However, the difference or the effect induced by the variation of the index to the surface diffusion seems to be relatively smaller as compared to that induced by the substrate temperature [35].

Bottom Line: Under an identical growth condition, the self-assembled Au droplets of mini to supersizes are successfully synthesized via the Volmer-Weber growth mode.Depending on the DA, an apparent evolution is clearly observed in terms of the average height (AH), lateral diameter (LD), and average density (AD).In addition, accompanied with the dimensional expansion, the AD of Au droplets drastically swings on 2 orders of magnitudes from 3.2 × 10(10) to 4.2 × 10(8) cm(-2).

View Article: PubMed Central - HTML - PubMed

Affiliation: College of Electronics and Information, Kwangwoon University, Nowon-gu Seoul 139-701, South Korea.

ABSTRACT
The fabrication of self-assembled Au droplets is successfully demonstrated on various GaAs (n11)B, where n is 2, 4, 5, 7, 8, and 9, by the systematic variation of the Au deposition amount (DA) from 2 to 12 nm with subsequent annealing at 550°C. Under an identical growth condition, the self-assembled Au droplets of mini to supersizes are successfully synthesized via the Volmer-Weber growth mode. Depending on the DA, an apparent evolution is clearly observed in terms of the average height (AH), lateral diameter (LD), and average density (AD). For example, compared with the mini Au droplets with a DA of 2 nm, AH of 22.5 nm, and LD of 86.5 nm, the super Au droplets with 12-nm DA show significantly increased AH of 316% and LD of 320%, reaching an AH of 71.1 nm and LD of 276.8 nm on GaAs (211)B. In addition, accompanied with the dimensional expansion, the AD of Au droplets drastically swings on 2 orders of magnitudes from 3.2 × 10(10) to 4.2 × 10(8) cm(-2). The results are systematically analyzed with respect to the atomic force microscopy (AFM) and scanning electron microscopy (SEM) images, energy-dispersive X-ray spectrometry (EDS) spectra, cross-sectional line profiles, Fourier filter transform (FFT) power spectra, and root-mean-square (RMS) roughness as well as the droplet dimension and density summary, respectively.

No MeSH data available.


Related in: MedlinePlus