Systematic Study on the Self-Assembled Hexagonal Au Voids, Nano-Clusters and Nanoparticles on GaN (0001).

Puran Pandey,Jihoon Lee,Mao Sui,Eun-Soo Kim,Quanzhen Zhang,Ming-Yu Li,Sefer Bora Lisesivdin

doi:10.1371/journal.pone.0134637

Puran Pandey, Jihoon Lee + Show 5 more

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https://doi.org/10.1371/journal.pone.0134637

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Abstract

Au nano-clusters and nanoparticles (NPs) have been widely utilized in various electronic, optoelectronic, and bio-medical applications due to their great potentials. The size, density and configuration of Au NPs play a vital role in the performance of these devices. In this paper, we present a systematic study on the self-assembled hexagonal Au voids, nano-clusters and NPs fabricated on GaN (0001) by the variation of annealing temperature and deposition amount. At relatively low annealing temperatures between 400 and 600°C, the fabrication of hexagonal shaped Au voids and Au nano-clusters are observed and discussed based on the diffusion limited aggregation model. The size and density of voids and nano-clusters can systematically be controlled. The self-assembled Au NPs are fabricated at comparatively high temperatures from 650 to 800°C based on the Volmer-Weber growth model and also the size and density can be tuned accordingly. The results are symmetrically analyzed and discussed in conjunction with the diffusion theory and thermodynamics by utilizing AFM and SEM images, EDS maps and spectra, FFT power spectra, cross-sectional line-profiles and size and density plots.

Highlights

Au nanoparticles (NPs) have attracted significant research interests due to their potential applications in solar cells,[1,2] memories,[3] sensors,[4] and bio-medical devices[5,6] owing to their localized surface plasmon resonance, increased absorption, enhanced fluorescence and scattering properties.[1,2,3,4,5,6] The performance of corresponding devices are strongly dependent on the size and density of Au NPs
The atomic force microscopy (AFM) top-views, cross-sectional line profiles and Fourier filter transform (FFT) power spectra are presented in Fig 2 and the corresponding 3-diffusion coefficient (Ds) AFM side-views are shown in S3 Fig Between 400 and 600°C of annealing, two distinct phases have been observed: formation of the Au voids and nano-clusters
The metal films of Ag, Cu, Fe, Ag-Ni at low temperature annealing demonstrated the formation of voids on various substrates. [30,31,32,33] as presented in Fig 2(C), due to the increased diffusion length at 600°C, the Au clusters were fabricated based on the diffusion limited aggregation (DLA) model

Summary

Introduction

Au nanoparticles (NPs) have attracted significant research interests due to their potential applications in solar cells,[1,2] memories,[3] sensors,[4] and bio-medical devices[5,6] owing to their localized surface plasmon resonance, increased absorption, enhanced fluorescence and scattering properties.[1,2,3,4,5,6] The performance of corresponding devices are strongly dependent on the size and density of Au NPs. For example, Au NPs exhibit the localized surface plasmon resonance property that enhances the light absorption so there is significant improvement in the efficiency of solar cells.[1] Comparatively large Au NPs can produce higher power conversion efficiency.[1,2] small size of Au NPs with the increased density allows improving the turn-on voltages and on/off current ratios in the nanofiber-based memory devices.[3] the arrays of spherical large-scaled Au NPs can be used in the laser

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Conclusion