EN
Focused electron beam induced deposition
presents a promising technique for the fabrication of
nanostructures. However, due to the dissociation of
mostly organometallic precursor molecules employed for
the deposition process, prepared nanostructures contain
organic residues leading to rather low conductance of
the deposits. Post-growth treatment of the structures by
electron irradiation or in reactive atmospheres at elevated
temperatures can be applied to purify the samples.
Recently, an in-situ conductance optimization process
involving evolutionary genetic algorithm techniques has
been introduced leading to an increase of conductance
by one order of magnitude for tungsten-based deposits
using the precursor W(CO)6. This method even allows for
the optimization of conductance of nano-structures for
which post-growth treatment is not possible or desirable.
However, the mechanisms responsible for the observed
enhancement have not been studied in depth. In this
work, we identified the dwell-time dependent change of
conductivity of the samples to be the major contributor
to the change of conductance. Specifically, the chemical
composition drastically changes with a variation of dwelltime
resulting in an increase of the metal content by 15
at% for short dwell-times. The relative change of growth
rate amounts to less than 25 % and has a negligible
influence on conductance. We anticipate the in-situ
genetic algorithm optimization procedure to be of high
relevance for new developments regarding binary or
ternary systems prepared by focused electron or ion beam
induced deposition.