Structural dynamics of gas-phase molybdenum nanoclusters: A transmission electron microscopy study

Abstract

In this paper we study structural aspects of molybdenum clusters by transmission electron microscopy. The deposited clusters with sizes 4nm or larger show a body-centered crystal (bcc) structure. The clusters are self-assembled from smaller structural units and form cuboids with a typical size of 4nm or larger. With reducing cluster size, the face-centered crystal (fcc) structure appears due to dominance of surface energy minimization, while self-assembly into large cuboids with sizes up to 30nm is still observed. Our observation implies that the basic building blocks of large cuboids are actually not smaller cubes. Annealing leads to cluster coalescence at temperatures ∼800°C, with the crystal habit changing to truncated rhombic dodecahedron for isolated clusters, while the large cuboidally shaped particles become more faceted polyhedra.

Stress relaxation induced faceted Cu and W particles on the surfaces of Cu–Zr and W thin films

“…Compared to the nanoclusters by sputtering deposition [16][17][18], the bigger size of the regular faceted Cu particles can be attributed to the fact that the thin films can provide sufficient atoms for their continuous growth through the diffusion along grain boundaries. As demonstrated by Hwang et al [4], the sizes of faceted Cu particles may be changed by adjusting the film thickness and annealing temperature.…”

“…Recently, many experiments and computer simulation are performed on nanosized clusters and submicron-scale metal pillars and particles to investigate the intrinsic properties of materials [12][13][14][15][16][17][18]. The results demonstrated that their physical, chemical and mechanical properties apparently differ from those of corresponding bulk ones.…”

Opportunities from the nanoworld: Gas phase nanoparticles

“…The ability to control surface feature on this length scale is essential in future nanotechnology. Deposition of nanoparticles has emerged as an important technique to assemble nanostructures [7][8][9][10][11][12][13][14]. The main challenges are to produce size-selected nanoparticles, and to control the interaction with the substrate so that the original nanoparticle properties are being preserved.…”

“…Furthermore, for magnetic nanoparticles [3,4,[11][12][13][14][15][16][17][18][19][20][21][22] magnetic anisotropy generates magnetic easy axes with an energy barrier separating different orientations of the magnetic moment. Without an external field the magnetic moment is in a blocked state, unless thermal activation is able to overcome the anisotropy energy barrier and induce moment flipping in between easy directions (super-paramagnetism).…”

“…Small nanoparticles have a tendency to form larger nanoparticles in a process called sintering. Furthermore, in order to explore the mechanisms of structural evolution (and establish a microstructure-property relationship) in situ observations of particle crystal habit, structure, sintering and oxidation are highly indispensable [8][9][10][11][12][13][14].…”