The photosensitivity of nanocomposite AlN films with embedded silver nanospheres is reported. It stems from localized surface plasmon resonances (LSPR) whose modulation is photoinduced by laser annealing that induces a combined effect of metallic nanoparticle enlargement and dielectric matrix recrystallization; the photoindunced changes of the refractive index of the matrix result in strong spectral shift of LSPR. We demonstrate the utilization of this process for spectrally selective optical encoding into hard, durable, and chemically inert films.
Yttrium oxide dielectric films were grown by rf-magnetron sputtering on n-Si(100) substrates and annealed in vacuum at temperatures ranging from 400 to 600°C. The main aim of this work was the investigation of the interface between the dielectric film and silicon. Both structural ͑x-ray diffraction and transmission electron microscopy͒ and electrical characterization were used for this purpose. No structural change was observed on the interfacial native oxide layer after annealing at 600°C for 1 h. Metal-oxide-semiconductor structures defined by the evaporation of Al electrodes show low leakage currents, moderate dielectric constant ͑around 14͒, and high densities of positive charges trapped in the oxide. Hysteresis effects in capacitance-voltage (C -V) curves reduce with the annealing temperature. Another interesting observation is the parallel shift of the C -V curves along the voltage axis with frequency. An insulator trap model is proposed to explain this behavior.
Nano-structuring of metals is one of the greatest challenges for the future of plasmonic and photonic devices. Such a technological challenge calls for the development of ultra-fast, high-throughput and low-cost fabrication techniques. Laser processing, accounts for the aforementioned properties, representing an unrivalled tool towards the anticipated arrival of modules based in metallic nanostructures, with an extra advantage: the ease of scalability. In the present work we take advantage of the ability to tune the laser wavelength to either match the absorption spectral profile of the metal or to be resonant with the plasma oscillation frequency, and demonstrate the utilization of different optical absorption mechanisms that are size-selective and enable the fabrication of pre-determined patterns of metal nanostructures. Thus, we overcome the greatest challenge of Laser Induced Self Assembly by combining simultaneously large-scale character with atomic-scale precision. The proposed process can serve as a platform that will stimulate further progress towards the engineering of plasmonic devices.
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