Study of porous carbon thin films produced by pulsed laser deposition

Amorphous carbon is an interesting material and its properties can be varied by tuning its diamond-like (sp³) fractions. The diamond-like fractions in an amorphous carbon films depends on the kinetic energy of the deposited carbon ions. Porous amorphous carbon thin films were deposited onto silicon substrates at room temperature in a vacuum chamber by Glancing Angle Pulsed Laser Deposition (GAPLD). Krypton fluoride (248 nm) laser pulses with duration of 15 ns and intensities of 1-20 GW/cm² were used. In GAPLD, the angles between the substrate normal and the trajectory of the incident deposition flux are set to be almost 90°. Porous thin films consisting of carbon nanowires with diameters less than 100 nm were formed due to a self-shadowing effect. The kinetic energies of the deposited ions, the deposition rate of the films and the size of the nanowires were investigated. The sp³ fraction of the porous carbon films produced at intensity around 20 GW/cm² were estimated from their Raman spectra.