  We report on an investigation on the properties of ultra-low density,
fractal, Carbon nanofoams fabricated with the nanosecond and femtosecond
pulsed-laser deposition (PLD) techniques. We measure through innovative
techniques the foam mean density and the properties of the fractal aggregates
composing the film (i.e. nanoparticles diameter, fractal dimension, and
gyration radius) as a function of several PLD process parameters, namely the
background gas pressure and the laser pulse characteristics (energy, time
duration, repetition rate). We discuss the experimental observation on the
basis of the existing literature, and we propose an analytical equation, based
on the fractal scaling law, to predict the foam density from the aggregates
properties. Finally, we use analytical arguments to explain the observed trends
in the nanofoam density with respect to the process parameters, useful to gain
new insights on the nanofoam growth and to guide experimental work in
fabricating ultra-low density films with precisely controlled properties.
