Influence of substrate temperature and atmosphere on nano-graphene formation and texturing of pulsed Nd:YAG laser-deposited carbon films

Pulsed laser ablation of a pyrolytic graphite target (Nd:YAG laser, second harmonic: lambda = 532 nm, hv = 2.33 eV. tau = 7 ns, nu = 10 Hz, Phi approximate to 7 J/cm(2)), operating at different experimental conditions (i.e. fluence, substrate temperature, working pressure, inert sustaining gases) has been used to prepare films of nano-structured carbon. Detailed characterisation of synchrotron X-ray measurements, performed at grazing incidence, established the formation of nano-sized graphene structures at high deposition temperatures (similar to 900 degrees C). A longitudinal growth of parallel graphene layers, with (c) over tilde axis parallel to the substrate, was also attained when the plume of activated carbon species was allowed to expand in the vacuum (base level similar to 5 x 10(-4) Pa). The presence of He sustaining gas, on the other side, gave rise to nano-graphitic particles, but with their e axis randomly oriented in the film. The mass density of the deposited films, as measured by laboratory X-ray reflectivity (XRR), is also strongly dependent on the experimental settings: films grown in the inert gas have density lower than the vacuum-deposited films. The highest density was obtained at room temperature, where an amorphous carbon structure is formed.