Experimental and numerical study on pulsed-laser annealing process of diamond-like carbon thin films

The diamond-like carbon (DLC) films were deposited by KrF excimer laser (la mbda = 248 nm) ablation under H-2 atmosphere of 200 mtorr with 6 J/cm(2). T he prepared DLC thin film was mounted on the holder and the film surface wa s irradiated with the third harmonic of a single pulsed of Nd:YAG laser (la mbda = 355 nm) or a pulsed KrF excimer laser. The experiments were performe d in air and the substrate was held at room temperature. The threshold ener gy density for surface damage is measured by inspecting the surface after a single laser shot of increasing fluence to observe the onset of surface da mage. The damage threshold energy density for DLC film flashed by a pulsed Nd:YAG laser is in the range 60-50 mJ/cm(2). The dynamics of pulsed nanosec ond laser heating process is simulated by the solution of the one-dimension al heat conduction equation. The finite element method (FEM) is applied to solve the equation. At the laser fluence of 80 mJ/cm(2) with the Nd:YAG las er, the surface reaches the maximum temperature of 785 degreesC at 48 ns. T he experimental and calculated results show that the damage temperature of DLC film is smaller than the vaporization temperature of solid carbon. More over, the transmission spectra of DLC films before and after irradiation we re measured. The graphitization occurred on the sample after irradiation ov er threshold energy for surface damage. (C) 2001 Elsevier Science B.V. All rights reserved.