Aligning one-dimensional arrays of nanoclusters on a thin film of Al2O3 grown on vicinal NiAl surfaces

Growth of Al2O3 Nanowires on the Cu‐9 at.%Al(111) Single Crystal Surface

“…Studies of thin alumina film growth and structures have pointed to the formation of γ‐ and θ‐Al 2 O 3 layers on NiAl(001) and NiAl(110) single crystals. By oxidizing NiAl surfaces vicinal to the (100) plane tilted along crystallographic direction [010], Luo et al . have prepared θ‐Al 2 O 3 strips along [001] direction.…”

“…[12][13][14] Studies of thin alumina film growth and structures [13][14][15] have pointed to the formation of γand h-Al 2 O 3 layers on NiAl(001) and NiAl(110) single crystals. By oxidizing NiAl surfaces vicinal to the (100) plane tilted along crystallographic direction [010], Luo et al 16 have prepared h-Al 2 O 3 strips along [001] direction. The formation of the ultra-thin well-ordered stoichiometric γ-Al 2 O 3 layer on the Cu-9 at.%Al(111) single crystal was reported with an optimal oxidation procedure by Yoshitake et al 14,[17][18][19] .…”

Investigation of Thermal Stability and Reactivity of Rh Nanoclusters on an Ultrathin Alumina Film

“…Figure 1a-d exemplify the evolution of the size and density of smaller Rh clusters/Al 2 O 3 /NiAl(100) with annealing temperature; the insets in the figures show, for each temperature, the characteristic histograms of height and diameter of the clusters; a Gaussian fit to the size distribution is also shown in each histogram. At 300 K, the 0.5 monolayer equivalent (MLe) Rh clusters had a mean diameter about 1.4 nm and height about 0.6 nm ( Figure 1a); the clusters were largely aligned as the protrusions stripes, arising from a lattice mismatch between the Al 2 O 3 film and NiAl(100) [42][43][44], are preferential nucleation sites, as observed earlier for other deposited transition metals [44][45][46]. With the temperature increased to 450 K, both the mean diameter and height altered little ( Figure 1b); the cluster density also remained similar (1.66 × 10 13 cm −2 ).…”

“…The quantity decreased evidently with temperature above 570 K ( Figure 3c); at 800 K, the quantity decreased to below 50% of the original. The decrease reflects that Rh atoms from dissociated clusters diffused into the substrate, likely through surface defects [4,[42][43][44]. Like the cluster diameter, the cluster density exhibited atypical behaviors.…”

“…The atypical alteration of cluster size and density could result solely from a kinetic effect or involve an energetic one. The former argues an Ostwald ripening constrained by the channel of Rh diffusion to the substrate and facile formation of new clusters due to abundant preferential nucleation sites, the linear protrusions, on the Al2O3/NiAl(100) [10,[44][45][46]. For 0.5-MLe Rh, the Rh atoms from dissociated Rh clusters diffused largely into the substrate above 570 K (instead of joining existing clusters) because of its small cluster density, so the cluster size decreased and no typical sintering occurred.…”