Laser deposition of diamondlike carbon films at high intensities

Unhydrogenated diamondlike carbon (DLC) thin films have been deposited by laser ablation of graphite, using a high power Ti: sapphire solid state laser system. DLC films were deposited onto silicon substrates at room temperature with subpicosecond laser pulses, at peak intensities in the 4×10 ¹⁴-5×10¹⁵W/cm² range. A variety of techniques, including scanning and transmission electron microscopy (SEM and TEM), Raman spectroscopy, spectroscopic ellipsometry (SE), and electron energy loss spectroscopy (EELS) have been used to analyze the film quality. Smooth, partially transparent films were produced, distinct from the graphite target. Sp³ volume fractions were found to be in the 50%-60% range, with Tauc band gaps ranging from 0.6 to 1.2 eV, depending on laser intensity. Kinetic energies carried by the carbon ions in the laser induced plasma were measured through time-of-flight (TOF) spectroscopy. Their most probable kinetic energies were found to be in the 700-1000 eV range, increasing with laser intensity.