Microstructure of FePt nanoparticles produced by nanocluster beam

Abstract

FePt nanoparticles produced by condensation of sputtered atoms in a nanocluster beam source at different forming temperatures were investigated using transmission electron microscopy (TEM). At the temperature of 170 K, the particles were icosahedron and the mean particle size was 4 nm with a standard deviation of 16%. At 100 K polygonal shapes of particles with size 5–15 nm such as triangular, square, rhombic, pentagonal, hexagonal, octagonal, and irregular were observed. The three-dimensional (3-D) shapes of the 2-D TEM projections were derived from high resolution, bright field, dark field and weak beam dark field (WBDF) imaging and electron diffraction pattern. The polygonal shapes arose from octahedron, truncated octahedron, cubooctahedra, truncated tetrahedron, triangular platelet, Marks decahedron and icosahedron. The final growth structures did not necessarily have the lowest free energy, but was the one that corresponded to a local minimum governed by specific growth kinetics.