Laser Assisted Electrodeposition of Metals and Alloys

Laser sources are extensively used in surface engineering technology and in materials processing. Their high energy density, excellent directionality and monochromaticity makes them ideal for a wealth of potential uses that require the concentration of a significant amount of energy in a small area. From the electrochemical point of view, one of the most interesting applications for lasers is Laser Assisted Electrodeposition (LAE). Indeed, the high energy density transferred by a laser can locally change the electrochemical state of a surface by inducing photo-electrochemical or thermal-electrochemical effects, triggering thus metal reduction. In addition, it is also possible to pattern the deposited metal layer by scanning the surface of the substrate with the laser, usually with spatial resolution in the range of few micrometers. From the applicative point of view, LAE can be exploited for the selective deposition of metal layers for both decorative and functional uses. LAE can be intended in two ways: the laser can be used to enhance a standard electrolytic deposition process [1, 2], increasing deposition rates by focusing the radiation on the cathode, or it can be used to trigger electrodeposition on freestanding metal surfaces in total absence of any external polarization [1]. The latter approach is the most interesting due to the reduced complexity of the setup required and is made possible by the localized variation of the rest potential induced in the zone of the substrate hit by the light [1]. As a consequence of this variation, metallic ions can be reduced in correspondence of the illuminated zone. The occurrence of this phenomenon, which allows metal deposition without any external power source, has been demonstrated for Cu [1, 3], Ni [3] and Au [4]. Despite the work carried out by many research groups, still many aspects of LAE in absence of external polarization remain poorly understood. The aim of the present work is to investigate the possibility to perform LAE with some significant metal-substrate couples. The deposition mechanism is rationalized considering the specific electrochemical properties of the metals involved. In addition to this fundamental characterization, the work also aims at evaluating the industrial applicability of LAE. To this extent, patterned layers of precious metals are deposited on metallic substrates for decorative purposes. Finally, LAE is applied here for the first time to the deposition of alloys.