Influence of electric field on laser damage properties of DLC films by unbalanced magnetron sputtering

Abstract

DLC films with different thicknesses were prepared on Si substrates by the unbalanced magnetron sputtering (UBMS) method using the same experimental parameters to investigate the relationship between electric field intensity distribution and laser damage properties of the samples. The results indicated that different electric field intensity distributions in the films cause diverse laser damage properties. For the DLC films with optical thicknesses of 287, 341, 421 and 545.9nm, the electric field intensity (normalized electric field intensity squared) at the film–air interface is 0.9407, 0.7709, 0.4298 and 0.2241 respectively when at the wavelength of 1064nm. Under the same high-energy laser irradiation, the size of cracked spots of the film with a lower electric filed intensity is smaller than that with higher electric field intensity. The laser-induced damage threshold (LIDT) of the DLC samples is 0.6, 0.8, 1.2 and 1.5J/cm2 respectively (1064nm, 10ns). This shows that a higher LIDT may be obtained provided the films have lower electric field intensity at the film–air interface. Therefore, the laser damage-resistance ability of the films can be improved by optimizing the electric field to one with lower intensity during the process of film stack design and materials matching.