Pulsed laser deposition of carbon nanofoam

Abstract

We present a comprehensive study about the fabrication of porous, fractal-like nanostructured carbon materials, known as carbon nanofoam, through the Pulsed Laser Deposition (PLD) technique with nanosecond (ns-PLD) and femtosecond (fs-PLD) laser pulses ablating a pyrolitic graphite target. Carbon nanofoams have attracted considerable interest for applications of great societal and technological relevance. Among different fabrication methods, PLD emerged as a versatile tool that allows the depositon of nanostructured films on virtually any kind of substrate. Here we investigate the role of key PLD parameters (laser pulse duration and fluence, background gas pressure) on nanofoam characteristics, with a specific focus on how fractal aggregate properties at the nanometric scale (nanoparticle size, fractal dimension, gyration radius) determine nanofoam averaged properties such as density and uniformity. We performed systematic deposition campaigns and characterizations through experimental analysis and mathematical models. Moreover, a first-of-its-kind comparison between ns-PLD and fs-PLD regimes is drawn. We discuss the physics of foam growth in both regimes, and we propose an analytical model based on the fractal scaling law to predict the nanofoam density from aggregates’ properties. The new insights gained about deposition and characterization of carbon nanofoam open new perspectives in fabrication of nanostructured films with precisely controlled properties.