Final Report Summary - LASER-PLASMON (LASER manipulation of PLASMONic nanostructures)
Photonics promise processing of information in the fastest possible way. A photon can be considered as the ultimate messenger because it has no mass. So, one can pack it with much information and propagate it with the ultimate speed, which is the speed of light. Electrons, on the other hand, cannot move as fast since they have mass. Photonics is essentially faster means of processing information and therefore will dominate the future of processing devices. It is however difficult to manipulate photons, since they cannot be charged; in that sense it is much easier to manipulate electrons (through an external field). But, there are some brilliant ideas with which you can manipulate light. Plasmons are density waves of electrons, created when light hits the surface of a metal under precise circumstances. These waves are generated at optical frequencies, can be confined within a very small space and they decay rapidly. They can theoretically encode a lot of information, more than what is possible for conventional electronics.
This ability of metal nanostructures to manipulate light at the nanoscale has resulted in an emerging research area called plasmonics. Over the past decade plasmonics has developed into a rapidly maturing and broad research field, and it is now progressively becoming an enabling technology involving an overwhelming number of interesting concepts, such as chemical and biomedical sensing, information and communication technologies, solar energy harvesting, lighting, cancer treatment and surface decorations to name a few. This makes the field extremely interesting and important as the applications involve all aspects of everyday life.
However we are still far away from the point where these exciting applications will become commercial products. This is mainly due to manufacturing complexity and high cost that current technology has. In particular, current used techniques have followed two distinct routes: the top-down approach, which offers unparalleled control and reproducibility down to a few nm in feature size, but at high cost for large area processing, and the bottom-up approach, which naturally applies for macroscopic scale nanopatterning albeit without the fine feature and reproducibility control. LASER-PLASMON addresses the central challenge of robust and accurate fabrication of nanostructures over large areas, with reproducible and predictable optical properties. This fabrication technique is a photonic process, namely laser annealing, a less complex patterning tool providing freedom of design, fast processing, compatibility with large-area manufacturing that allows for the use of inexpensive flexible substrates.
LASER-PLASMON has developed and optimized seed materials for plasmonic nanostructuring via LA. These materials include single metallic thin films (Cu, Ag, Au), composite and multilayer structures of metals (Ag, Au) with passive (Y2O3, AlN) and active (TiO2, TiOxNy and ZnO) ceramics. The term active ceramics stems from the reaction/activity of the ceramic material against electromagnetic radiation (e.g. TiO2 is well known photocatalyst, w-ZnO is known as luminescent material). The project has identified the most appropriate LA system design and processing parameters to develop nanostructures of the above mentioned materials that sustain plasmonic response. LASER-PLASMON investigated the underlying mechanisms during LA and their related opto-electronic properties. Finally, it has delivered a free web based experimental library (DOLFIN: Database Of Laser Fabricated Innovative Nanostructures) that will facilitate the future development of plasmonic applications. This database is hosted at the project’s official website: www.laserplasmon.com. In the framework of the project we have:
- Identified a laser process window for tailoring the localized surface plasmon resonance (LSPR) in various metallic systems and multilayer structures.
- Exploited the size-dependent optical absorption and thermal dissipation of the plasmonic nanoparticles, enabling their selective melting and re-solidification, to produce plasmonic templates of predefined morphology and optical response by laser irradiation.
- Different optical absorption and heat diffusion mechanisms in metal nanoparticles were exploited as a means of controlling matter at the nanoscale, via laser driven processes for restructuring a metal thin film into a predetermined nanoparticle template. The stochastic recrystallization of melted metal nanoparticles is broken by the size-selectivity in optical absorption and heat dissipation, providing an exceptional potential for selective formation of nanoparticles with predesigned and desired size distributions. As a result, successive pulses of UV laser annealing reduce the volume fraction of larger nanoparticles (>50 nm), while VIS laser annealing may either further refine the size distributions or induce the emergence of nanoparticles, which exhibit LSPR close to the irradiation wavelength. This combined UV and VIS laser annealing treatment provides unprecedented control on the size distributions and plasmonic behaviour of nanoparticle arrays of noble metals (Ag, Au, Cu) independently of their deposition method.
- Demonstrated the versatility of laser processing for the sub-surface control and modification of metal plasmonic nanostructures in stratified metal/dielectric media. UV-laser processing of multilayer films is sensitive to the thermal conductivity (k) of the ceramic phase. High k materials lead to a constant temperature profile within the multilayer structure, upon laser processing, leading to homogeneously sized dispersed nanoparticles in the reformed structure. On the contrary lower k materials lead to a significant gradient in temperature profile across the multilayer, with higher temperature close to the free surface and lower close to the substrate, resulting into different annealing structures. It was identified that 3 or 4 bilayers are enough for an effective laser annealing reconstruction featuring a plasmonic response. By the same token, for fewer bilayers cooling through the substrate would be more effective and higher laser fluence is required.
- Exploited the applicability of the laser annealing produced materials to opto-electronic devices such as: photocatalytic templates towards withholding of heavy metal ions from aqueous solutions (Mn, As), organic photovoltaic devices and enhanced photoluminsence of ZnO. An initial approach towards nanocrystal memory devices, based on Y2O3/Ag nanoparticles, has been realized.
Overall LASER-PLASMON has developed and demonstrated novel nano-structured plasmonic materials produced by an alternative technique, namely laser annealing, as a fabrication platform that will benefit plasmonic technology, by breaking the current barrier to improved production costs for large-area manufacturing and will potentially lead to faster end-product fabrication that will have a huge impact to society. A brief summary of a few key results of the LASER-PLASMON project are illustrated in figure 1.
This ability of metal nanostructures to manipulate light at the nanoscale has resulted in an emerging research area called plasmonics. Over the past decade plasmonics has developed into a rapidly maturing and broad research field, and it is now progressively becoming an enabling technology involving an overwhelming number of interesting concepts, such as chemical and biomedical sensing, information and communication technologies, solar energy harvesting, lighting, cancer treatment and surface decorations to name a few. This makes the field extremely interesting and important as the applications involve all aspects of everyday life.
However we are still far away from the point where these exciting applications will become commercial products. This is mainly due to manufacturing complexity and high cost that current technology has. In particular, current used techniques have followed two distinct routes: the top-down approach, which offers unparalleled control and reproducibility down to a few nm in feature size, but at high cost for large area processing, and the bottom-up approach, which naturally applies for macroscopic scale nanopatterning albeit without the fine feature and reproducibility control. LASER-PLASMON addresses the central challenge of robust and accurate fabrication of nanostructures over large areas, with reproducible and predictable optical properties. This fabrication technique is a photonic process, namely laser annealing, a less complex patterning tool providing freedom of design, fast processing, compatibility with large-area manufacturing that allows for the use of inexpensive flexible substrates.
LASER-PLASMON has developed and optimized seed materials for plasmonic nanostructuring via LA. These materials include single metallic thin films (Cu, Ag, Au), composite and multilayer structures of metals (Ag, Au) with passive (Y2O3, AlN) and active (TiO2, TiOxNy and ZnO) ceramics. The term active ceramics stems from the reaction/activity of the ceramic material against electromagnetic radiation (e.g. TiO2 is well known photocatalyst, w-ZnO is known as luminescent material). The project has identified the most appropriate LA system design and processing parameters to develop nanostructures of the above mentioned materials that sustain plasmonic response. LASER-PLASMON investigated the underlying mechanisms during LA and their related opto-electronic properties. Finally, it has delivered a free web based experimental library (DOLFIN: Database Of Laser Fabricated Innovative Nanostructures) that will facilitate the future development of plasmonic applications. This database is hosted at the project’s official website: www.laserplasmon.com. In the framework of the project we have:
- Identified a laser process window for tailoring the localized surface plasmon resonance (LSPR) in various metallic systems and multilayer structures.
- Exploited the size-dependent optical absorption and thermal dissipation of the plasmonic nanoparticles, enabling their selective melting and re-solidification, to produce plasmonic templates of predefined morphology and optical response by laser irradiation.
- Different optical absorption and heat diffusion mechanisms in metal nanoparticles were exploited as a means of controlling matter at the nanoscale, via laser driven processes for restructuring a metal thin film into a predetermined nanoparticle template. The stochastic recrystallization of melted metal nanoparticles is broken by the size-selectivity in optical absorption and heat dissipation, providing an exceptional potential for selective formation of nanoparticles with predesigned and desired size distributions. As a result, successive pulses of UV laser annealing reduce the volume fraction of larger nanoparticles (>50 nm), while VIS laser annealing may either further refine the size distributions or induce the emergence of nanoparticles, which exhibit LSPR close to the irradiation wavelength. This combined UV and VIS laser annealing treatment provides unprecedented control on the size distributions and plasmonic behaviour of nanoparticle arrays of noble metals (Ag, Au, Cu) independently of their deposition method.
- Demonstrated the versatility of laser processing for the sub-surface control and modification of metal plasmonic nanostructures in stratified metal/dielectric media. UV-laser processing of multilayer films is sensitive to the thermal conductivity (k) of the ceramic phase. High k materials lead to a constant temperature profile within the multilayer structure, upon laser processing, leading to homogeneously sized dispersed nanoparticles in the reformed structure. On the contrary lower k materials lead to a significant gradient in temperature profile across the multilayer, with higher temperature close to the free surface and lower close to the substrate, resulting into different annealing structures. It was identified that 3 or 4 bilayers are enough for an effective laser annealing reconstruction featuring a plasmonic response. By the same token, for fewer bilayers cooling through the substrate would be more effective and higher laser fluence is required.
- Exploited the applicability of the laser annealing produced materials to opto-electronic devices such as: photocatalytic templates towards withholding of heavy metal ions from aqueous solutions (Mn, As), organic photovoltaic devices and enhanced photoluminsence of ZnO. An initial approach towards nanocrystal memory devices, based on Y2O3/Ag nanoparticles, has been realized.
Overall LASER-PLASMON has developed and demonstrated novel nano-structured plasmonic materials produced by an alternative technique, namely laser annealing, as a fabrication platform that will benefit plasmonic technology, by breaking the current barrier to improved production costs for large-area manufacturing and will potentially lead to faster end-product fabrication that will have a huge impact to society. A brief summary of a few key results of the LASER-PLASMON project are illustrated in figure 1.
