Fig 1.
Illustration of the fabrication of hexagonal voids and self-assembled Au nanostructures on GaN (0001) by the variation of annealing temperature.
(a) Atomic force microscopy (AFM) top-view of a bare GaN (0001). (b) Surface morphology after the deposition of 5 nm Au. (c) Voids formation after the annealing at 400°C for 300 s. (d) Au nano-clusters observed at 600°C (e) Self-assembled Au NPs fabricated at 750°C. The AFM top-views (a)—(b) are 1 × 1 μm2 and that of top-views (c)—(e) are 5 × 5 μm2. (a-1)—(e-1) Cross-sectional surface line-profiles obtained from the white lines. (c-2)—(e-2) AFM 3-D views of hexagonal void, Au nano-cluster and Au NPs acquired from the regions denoted with green squares. (c-3) Atomic crystal structure of GaN (0001).
Fig 2.
Formation of hexagonal voids and Au nano-clusters on GaN (0001) by the annealing temperature variation between 400 and 600°C for 300 s with 5 nm Au deposition.
(a)—(c) AFM top-views of 20 × 20 μm2 with insets of 5 × 5 μm2. (a-1)—(c-1) Cross-sectional surface line-profiles obtained from the white lines. (a-2)—(c-2) Fourier filter transform (FFT) power spectra.
Fig 3.
Evolution of self-assembled Au NPs on GaN (0001) by the variation of annealing temperature between 650 and 800°C for 300 s with 5 nm of Au deposition.
(a)—(d) AFM top-views (20 × 20 μm2) with the insets (5 × 5 μm2). (a-1)—(d-1) Cross-sectional surface line-profiles acquired from the insets in (a)—(d). (a-2)—(d-2) FFT power spectra. (e) Plot of average height (AH) and average density (AD). (f) Plot of lateral diameter (LD). Error bars: ± 5%.
Fig 4.
Self-assembled Au NPs with an increased Au deposition amount of 10 nm on GaN (0001) between 700 and 800°C for 300 s.
(a)—(c) AFM top-views of 20 × 20 μm2 containing smaller scale AFM top-view insets of 5 × 5 μm2. (a-1)—(c-1) Cross-sectional surface line-profiles obtained from the white lines. (a-2)—(c-2) FFT power spectra.
Fig 5.
Energy dispersive X-ray spectroscopy (EDS) maps of self-assembled Au NPs with 10 nm of Au deposition annealed at 750°C for 300 s.
(a) SEM image. (b) 2-D phase maps of Au. (c)–(d) Au and Ga compositional maps of 3-D top-view. (e)–(f) EDS spectra of particular region marked with the green and blue square in (a). (g)–(h) EDS line-profiles acquired from the red lines in specific region in (a).
Fig 6.
Self-assembled Au NPs fabricated on GaN (0001) with 4 nm Au deposition by the variation of annealing temperature between 650 to 800°C for 300 s.
(a)—(d) AFM top-views of 20 × 20 μm2 with insets of 5 × 5 μm2. (a-1)—(d-1) Cross-sectional surface line-profiles acquired from the white lines. (a-2)—(d-2) FFT power spectra.
Fig 7.
Summary plots of (a) average height, (b) lateral diameter and (c) average density of self-assembled Au NPs fabricated by the variation of annealing temperature (Ta) along with the variation of Au deposition (DA) on GaN (0001).
Error bars: ± 5%.