Surface characterisation of nano-structured carbon films deposited by Nd:YAG pulsed laser deposition

Abstract Nano-structured carbon films have been proved to be outstanding materials for different kinds of applications, mainly electronic, owing to their high electron field emission properties, but also energetic (hydrogen storage, fuel cells), catalytic (very high metal catalyst dispersion properties) or biological (very good bio-sensor support). In this work we studied the influence of experimental conditions (vs. substrate temperature, working pressure and inert sustaining gases) on the structure evolution of carbon films, from an almost amorphous material to nano-clustered graphene particles. The carbon films were grown by Pulsed Laser Ablation (Nd:YAG, 2nd harmonic: λ=532 nm, hν=2.33 eV, τ=7 ns, ν=10 Hz, Φ≈7 J/cm2), from a pyrolytic graphite target on Si substrates. PLD depositions were performed at increasing temperature, ranging from room temperature to 900 °C, both in vacuum and in He atmosphere, at ∼20 Pa. Near-edge X-ray absorption fine structure (NEXAFS) and Raman spectroscopy evidenced the aromatic ring formation and the clustering condensation process with increasing surface temperature. The surface roughness and morphology of films grown at different conditions have been characterised by atomic force microscopy (AFM) and scanning electron microscopy (SEM).