From the nucleation of wiggling Au nanostructures to the dome-shaped Au droplets on GaAs (111)A, (110), (100), and (111)B

Abstract

In this paper, the systematic evolution process of self-assembled Au droplets is successfully demonstrated on GaAs (111)A, (110), (100), and (111)B. On various GaAs substrates, self-assembled Au clusters begin to nucleate at around 300°C, and then, they develop into wiggly Au nanostructures at 350°C. Between 400°C and 550°C, the self-assembled dome-shaped Au droplets with fine uniformity are fabricated with various sizes and densities based on the Volmer-Weber growth mode. Depending on the annealing temperature, the size including the average height and lateral diameter and the density of Au droplets show the opposite trend of increased size with correspondingly decreased density as a function of the annealing temperature due to the difference in the diffusion length of adatoms at varied activation energy. Under an identical growth condition, depending on the surface index, the size and density of Au droplets show a clear distinction, observed throughout the temperature range. The results are systematically analyzed and discussed in terms of atomic force microscopy (AFM) images, cross-sectional line profiles, and Fourier filter transform (FFT) power spectra as well as the summary plots of the size and density.

From the Au nano-clusters to the nanoparticles on 4H-SiC (0001)

“…In brief, during the annealing between 500 and 700 °C the surface morphology underwent a drastic evolution from the flat Au thin film with only few nanometer modulation to the irregular Au nano-mounds with several hundred nanometers in height due to the enhanced surface diffusion as a function of temperature, which also can be equally observed with large-scale scanning electron microscopy (SEM) images in Fig S4. Similar evolution of the irregular Au nano-mounds can be observed on quartz substrate 34 , various GaAs 35 36 , sapphire 37 and soft polymeric substrates 38 .…”

Effect of Au thickness on the evolution of self-assembled Au droplets on GaAs (111)A and (100)

“…In this work, the self-assembled Au droplets on GaAs (100) again showed quite similar evolution trends compared to those on GaAs (111)A. Based on the previous work [ 43 ], when the annealing temperature was varied between 250°C and 550°C on GaAs (100) and (111)A, respectively, the Au droplets showed a clear distinction in terms of their size and density. Indeed, at a lower temperature range between 250°C and 350°C, droplets began to nucleate and develop into wiggly Au nanostructures.…”

“…Perhaps, it could be because the ideal surface energy values of GaAs (100) and (111) are quite in a similar range: 65 meV/Å 2 for GaAs (100) and 62 meV/Å 2 for GaAs (111), respectively [ 47 ]. And also, it could be because the L D of Au adatoms has a much more noticeable effect with the temperature variation based on the diffusion and the annealing temperature variation effect on various GaAs surfaces [ 43 ]. Namely, in this experiment, the size and density of Au droplets can be governed by thermal surface diffusion and the surface index can have a minor effect when the L D was fixed with a fixed annealing temperature.…”

The versatility of the dynamic hydrogen bubble template derived copper foam on the emerging energy applications: progress and future prospects

“…50–55 The development of well-integrated hierarchical porous structures, such as porous foams has immensely influenced the direction of electrochemical energy research with the help of their opulent beneficial physical features that facilitate fast surface reaction kinetics due to rapid charge transfer between the open-pore hierarchical morphology, which in turns enhances the ionic as well as electronic conductivity. 56–60 Remarkable examples include ultraporous carbon electrodes and graphene aerogels, which are the sole commercial electrode materials in the supercapacitor industry. 62–64 Another leading instance of porous networks in material science is mesoscopically ordered materials, such as brightly coloured crystalline colloidal arrays of intelligent polymer hydrogel films with switchable periodicity and diffraction patterns that have huge application potential in sensors or supercapacitors.…”