Prof. dr. Ir. A.J. Huis in' t Veld
January 2011 - January 2015
Materials for sustainable energy, laser processing of thin films, ultra short pulsed lasers, laser-material interaction
The urgent need for a more sustainable energy system has become apparent in everyday life. Development and rapid large-scale deployment of more efficient and sustainable energy technologies, as well as energy savings are essential building blocks for the solution of these problems. Advanced materials, in turn, are enablers for the development of new energy technologies. Materials availability and the development of advanced new materials, employing nanotechnology and other novel approaches, has rapidly become a key area field of interest for industries and policies worldwide. ADEM, the Advanced Dutch Energy Materials innovation lab, therefore acts at the heart of the potential solutions. Successful innovation requires the close and efficient cooperation between public and private stakeholders. Within ADEM, the Energy Center of the Netherlands (ECN) and the 3 Dutch Universities of Technology therefore work together closely with companies in the broad field of energy technology and the Dutch government. ADEM is organized in 6 research themes:
· Solar cells and modules
· Catalysts, membranes and separations
· Hydrogen production and fuel cells
· Wind energy
· Transport, transfer and storage of heat
Nowadays, laser processing has become an important aspect of industrial micromachining, where precision, selectivity and processing speed are key parameters to evaluate the efficiency of a process.
In micromachining, lasers are mainly adopted for ablation, which is the removal of material by laser irradiation via direct sublimation of the target material within the focused laser spot. For this application, it is especially convenient to use pulsed laser sources, where the power densities reached during the single pulses exceed the obtainable levels by continuous wave (cw) lasers.
In the last decade, the demand of machining with higher precision and selectivity drove the application of lasers toward the so called ‘cold ablation’, where the Heat Affected Zone (HAZ) around the removed material is effectively reduced and in some cases becomes negligible.
The latter requirements moved the laser industry and laser manufacturers to adapt to these new standards.
Ultra-short pulsed lasers, with pulse durations in the order of tens of femtoseconds up to tens of picoseconds, find here their main usage and are nowadays replacing nanosecond pulsed lasers for industrial applications where cold ablation is needed. In fact, decreasing the interaction time between a single laser pulse and the material reduces the propagation of heat during the absorption of the laser light. Therefore, a higher thermal selectivity is provided with shorter pulse durations.
However, ultra-short pulsed lasers can find different applications. The combination of higher depth selectivity and different timescales in the interaction with matter, compared to ns-pulsed lasers, opens to new possibilities.
Whereas the thermal depth selectivity confines the effect of the laser treatment to the top section of the target, the particular interaction between the ultra-short laser pulses and matter can lead to new structures, changing the material properties as well as the morphology. Therefore, ultra short-pulsed lasers can be adopted for surface texturing and, as a new exploit, also for depth selective heat treatments. Furthermore, this high depth selectivity is particularly suitable for processing of thin films, where an high accuracy as well as a good control of the heat input are crucially required not to thermally damage the film and/or the substrate.
To this specific end, knowledge of the effects of the laser treatment on the micro and macro scale properties of the films as well as a good understanding of the laser-matter interaction is hence needed for finding successful processing conditions.
An application of this new type of processes can be found, as a future prospect, for technologies adopting thin films, i.e. photovoltaics (PV).
ADEM Innovation lab: http://www.adem-innovationlab.nl/