The diffusion length (l D) can be defined as (where D is the surface diffusion coefficient and τ is the residence time), and the D has a strong proportional dependency on the substrate temperature (D ∝ T sub). RG7204 solubility dmso Then, driven by a high T sub, the l D can be significantly increased. In a thermodynamic equilibrium system, nanostructures tend to increase their dimensions by absorbing nearby adatoms to lower the surface energy until reaching the equilibrium in order to keep the energy of the whole system in the lowest state. Therefore, when more adatoms exist within the l D, the increased dimensions
of droplets can be expected. In terms of the uniformity, the color pattern of the FFT power spectrum represents the frequency of the height with a directionality. The FFT spectrum with the 2-nm DA in Figure 3a-1 showed a round shape due to the round shape of the droplets. With the 3-nm DA, a smaller core of the FFT pattern was observed due to the reduced height frequency associated with the reduced density in Figure 3b-1 as well as the AFM image in Figure 2b. Then, the FFT patterns in Figure 3c-1,d-1,e-1,f-1 with the increased DAs became smaller and smaller as the frequency of the height became narrower and uniform. In addition, flat tops of droplets were observed
with the line profiles of the DAs of 9 and 12 nm in Figures 3e,f and 5e,f. This is in strong contrast with the selleck round dome-shaped droplets at lower Molecular motor DAs. In the case of Si with the increased Au deposition amount, lateral growth of Au nanostructures occurred even with as low as approximately 5-nm DA and finally resulted in the formation of a merged Au layer at approximately 20-nm DA . However, in
this experiment, the droplets were still maintained even above 12-nm DA (not shown here). Although it is not very logical to compare GaAs and Si directly due to the different growth conditions such as temperature, from this result, it can be expected that the binding energy between Au adatoms and surface atoms (E i) is weaker on GaAs surfaces than on Si (111). In other words, with increased DAs, droplets with lateral dimension expansion (coalescence) would require much higher DAs. In terms of the surface roughness (R q) during the DA variation from 2 to 3 nm, the R q was increased from 6.22 to 11.63 nm along with the expansion of the droplet dimensions as shown in Figure 4d. With the gradually increased DAs, the R q in Figure 4d showed an increasing trend accompanied with increased droplet dimensions, 6.22 nm for the 2-nm DA and 11.63 for the 3-nm DA, and gradually increased to 24.37 nm at the 9-nm DA. Then, the R q was saturated and showed a decreasing trend from there, likely due to the dominance of density decrease over the dimensional increase. Figure 6 shows the EDS spectra of the surface elemental characterization and the related SEM images of 4- and 12-nm samples. Generally, the resulting EDS spectra showed similar spectra for Ga and As with 4- and 12-nm DA as expected.