Electron beam synthesis of 3D metal nanostructures from fluoride precursors

Abstract

ABSTRACTVarious metal fluoride crystals were subjected to electron beam irradiation at 200 and 300 kV using transmission electron microscopy in order to study in-situ fabrication of 3D metal nanostructures. Lithium fluoride, cobalt fluoride and aluminum fluoride salt fragments were chemically reduced and transformed by the electron beam to the corresponding metals. Using live video recording we observe that LiF crystals decompose in a unique way different to all other metal-halides. Li diffuses rapidly out of the salt crystal and covers its surface and the surrounding C-support film to many microns distance, where at random positions nucleation, growth and annihilation of Li nanorods and some nanospheres is observable. Decomposition of CoF2 also involves non-local synthesis of Co nanoparticles, mostly facetted, however, these are stable, without annihiliation, and their positioning seems to follow some degree of self-organisation. AlF3 transforms locally to Al grains inside the irradiated area only, and grain growth occurs to sizes proportional to the beam intensity. Findings are discussed in terms of displacement energy differences between the materials.