Studies On Depositing Of Metal Film By Femtosecond Laser Induce Forword Transfer

In this thesis, experimental studies on the micro-deposition of metal film by femtosecond laser-induced forward transfer (fs-LIFT) are presented. Mechanisms on interaction of femtosecond laser pulses with metal materials are studied. The main contents are classified as follows:1. The ablation processing of metal materials with femtosecond laser pulses were simulated by the 2D Two-Temperature Model. According to the characteristic of femtosecond laser ablation, the threshold fluence for single pulse ablation of copper and aluminium were calculated. And the dependence of the electronic-lattice coupling time on irradiated laser pulse energy was studied on the basis of the simulation of the electronic and lattice's temperature, which present a steady increase with increasing the pulse fluence. Besides, the ablation depth and the ablation radius of copper for single pulse ablation were calculated. And the dependence of the start ablation (phase explosion arises) time of copper and aluminium on irradiated laser pulse energy was studied. The simulation results indicate that the material jet due to phase explosion is earlier and the duration of ablation lasts is longer with increasing the pulse fluence. And at the same time, the ablation depth and the ablation radius of material were increased until saturation.2. Systemic experimental study on deposition of copper film by femtosecond laser-induced forward transfer had been accomplished for the first time, in which the important headway had been acquired experimentally. Consist: (a). The threshold fluence for transfer researches experimentally. The threshold fluences of copper thin film of 40, 80 and 450 nm in thickness had been ascertained. It is wise up that the material is transferred and deposited on to the acceptor substrate in the form of liquid droplet mainly as the laser fluence was slightly above the threshold fluence. The droplet formation for the thinner film was a result of blow-off of molten film from the quartz substrate by compressive stress of plasma when the free surface was melted. Whereas for the thick film the higher pressure of plasma made the free surface of solid phase burst out, which resulted in the phenomenon that not only the solid material was sputtered but also the morphology of deposited film in the liquid state was made irregular. (b). Influence of the pulse fluence on the size of deposited film. The experimental results show that at threshold fluence, a thinner film generates a larger-sized of ablated and deposited dot. (c). Influence of the pulse fluence on the morphology of deposited film. The three typical morphologies of deposited dots was shown. At single laser pulse fluence slightly above the threshold, the material is transferred and deposited onto the acceptor substrate in the form of liquid droplet. With the increasing of the energy, the morphology of the deposited dots became island-like and circular. Whenas for higher energies, the transferred dots show ring-like morphology. (d). Influence of the accept distance on the size and morphology of deposited film. The experimental results show that the diameters of deposited dots are inversely proportional to the accept distance for the thinner film as the accept distance is within the range of several ten micron. Whereas for the thicker film that are inversely proportional.3. Systemic experimental study on deposition of aluminium film by femtosecond laser-induced forward transfer had been accomplished for the first time, in which the important headway had been acquired experimentally. Consist: The threshold fluences of aluminium film of 150 and 500 nm in thickness had been ascertained. The influence of the pulse fluence on the size and morphology of deposited dots had been researched. And experimental study on the influence of laser focusing location on the size and morphology of deposited dots had been completed.4. Influence of various parameters on the fabrication of line and micro lattice patterns by fs-LIFT had been investigated experimentally, for example: space between dot and dot, laser fluence and the accept distance etc. And the various micro lattice patterns had been fabricated.