  Chemical vapour deposition (CVD) is an established method for producing
high-purity thin films, but it typically necessitates the pre- and
post-processing of a mask to produce structures. This paper presents a novel
maskless patterning technique that enables area selective CVD of gold. A
focused electron beam is used to decompose the metal-organic precursor
Au(acac)Me$_2$ locally, thereby creating an autocatalytically active seed layer
for subsequent CVD with the same precursor. The procedure can be included in
the same CVD cycle without the need for clean room lithographic processing.
Moreover, it operates at low temperatures of 80 {\deg}C, over 200 K lower than
standard CVD temperatures for this precursor, reducing thermal load on the
specimen. Given that electron beam seeding operates on any even moderately
conductive surface, the process does not constrain device design. This is
demonstrated by the example of vertical nanostructures with high aspect ratios
of around 40:1 and more. Written using a focused electron beam and the same
precursor, these nanopillars exhibit catalytically active nuclei on their
surface. Furthermore, they allow for the first time the precise determination
of the local temperature increase caused by the writing of nanostructures with
an electron beam.
