Thermal effects during focused electron beam induced deposition of nanocomposite magnetic-cobalt-containing tips

Focused electron beam induced deposition of tips with cobalt carbonyl is studied with respect to deposit composition and nanostructure. Increasing the beam current from 20 pA to 3 μA at 25 keV, increases the average Co content from 12 to 80 at.% and the initial vertical deposition rate from 2 to 45 nm/s. At the initial growth stage, tip deposits show a smooth surface. This is related to a carbon-rich nano-composite structure with dispersed Co nanocrystals of 1–2 nm in size as shown by transmission electron microscopy (TEM) investigations. With increasing tip length or larger beam currents, transitions to corrugated and polycrystalline surfaces are observed. The observed phenomena fit into heat dissipation estimations where the formation of deposits with high Co-content is attributed to local thermal precursor decomposition at the tip apex.