Pulsed Laser Deposition of Functionally Gradient Diamond-Like Carbon (DLC) Films Using a Picosecond Laser

Abstract

In the part 1, functionally gradient diamond-like carbon (FGDLC) films are fabricated using a novel pulsed laser deposition technique to enhance adhesion strength. A 355 nm picosecond laser beam is split into two beams, and the power of each split beam is changed individually by a motorized beam attenuator as a function of time. In this way, two laser beams with customized time-varying powers are available for ablating two different target materials. Two beams are irradiated on graphite and 316L stainless steel targets, respectively, in a vacuum chamber, and the produced dissimilar plasmas are mixed in space before they are deposited on a stainless steel 316L substrate. Using this method, we have built FGDLC films with a thickness of ~510 nm, where the composition changes gradually from stainless steel to DLC in the direction of deposition. We have confirmed that FGDLC films show much higher adhesion strength than normal DLC films. In the part 2, we experiment about nine different materials when laser irradiates each material. During laser ablation process two mass removal modes exist, melting and vaporization. Evaporation and homogeneous boiling are consist of vaporization. After the boiling temperature, evaporation starts from boiling point and homogeneous boiling starts near 90% of the critical point. From this theoretical background some experiments are conducted. And also we have found many properties for each material and sorted elements, which have similar properties except critical point. From this experiment, we observed different shapes of different materials.