Fractal Carbon nanofoams by nanosecond and femtosecond pulsed-laser deposition

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.