Pulsed laser ablation is steadily gaining popularity in micromachining to keep pace with the increasing demand for precision manufacturing and functional surfaces. However, efficient laser processing under atmospheric conditions primarily suffers from particle redeposition and therefore requires additional cleaning steps to obtain high surface quality. To reduce additional cleanings steps after manufacturing, laser ablation in liquid allows for a significant reduction in particle redeposition as particles rapidly cool down and penetrate into the liquid without stitching to the surface. However, laser ablation in liquid is accompanied by the complex interaction between the hot molten material, the generated plasma and the over-critical liquid in the ablation zone. During this interaction, chemical reactions at the surface can take place and cause a persistent change of surface chemistry. Since the surface chemistry is a key aspect for micromachining, the interaction has to be studied to determine whether laser processing in liquids can be a feasible alternative to laser processing under ambient atmospheric conditions while reducing the problem of redeposition. Here, we present the results on the change of surface chemistry by laser ablation in liquid of a pristine silicon substrate. The micromachining process is either performed in an aqueous or gaseous environment and studied in dependence of laser intensity. The changes in surface chemistry are evaluated by micro-Raman spectroscopy and EDX.
Ultrashort pulse laser ablation has become an important tool for material processing. Adding liquids to the process can be beneficial for a reduced debris and heat affected zone width. Another application is the production of ligand-free nanoparticles. By measuring the ablation rate of iron for femtosecond pulsed laser ablation in different solvents and solvent-mixtures, the influence of the solvent properties on the ablation process is studied. The ablation efficiency is quantified by measuring the ablation rate in dependency of the fluence from 0.05 J/cm2 up to 5 J/cm2 in water-ethanol and water-acetone mixtures which are varied in 25 % steps. The ablation rate is significantly influenced by the solvent-mixtures.
Laser pulses in the picosecond and femtosecond regime enable nearly non-thermal material processing where heat effects like molten pools and thermal tensions are often significantly reduced. However, a residual amount of laser energy transforms into heat. As a consequence cumulative multiple shot processing leads to heat accumulation and subsequently lower manufacturing accuracy. To increase the processing throughput without losing quality, it is important to optimize the laser pulse properties and the ablation strategy to further reduce thermal effects. Due to a low heat capacity in small structures, it is necessary to consider the substrate dimensions while performing micro- and nanoprocessing. In contrast to bulk material ablation, the heat dissipation is confined by the small heat capacity of microstructures. Especially for complex structures, it is time-consuming to find efficient processing parameters manually. For this reason, an in-situ evaluation system based on electrical resistivity measurements for on-line control of the ablation process was developed to optimize the laser parameters. In the work presented, the efficiency of 35 femtosecond pulsed laser ablation was evaluated on copper structures in the micrometer range. Furthermore, these results have been compared and evaluated with surface profiles measured by white-light interferometry.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.