Synthesis of bimetallic nanostructures by nanosecond laser ablation of multicomponent thin films in water

The paper presents results on nanosecond laser ablation of thin films immersed in a liquid. The thin films were prepared by consecutive deposition of layers of different metals by thermal evaporation (first layer) and classical on-axis pulsed laser deposition (second layer); Ni/Au, Ag/Au and Ni/Ag thin films were thus deposited on glass substrates. The as-prepared films were then placed at the bottom of a glass vessel filled with double distilled water and irradiated by nanosecond laser pulses delivered by a Nd: YAG laser system at lambda = 355 nm. This resulted in the formation of colloids of the thin films' material. We also compared the processes of ablation of a bulk target and a thin film in the liquid by irradiating a Au target and a Au thin film by the same laser wavelength and fluence (lambda = 355 nm, F = 5 J/cm(2)). The optical properties of the colloids were evaluated by optical transmittance measurements in the UV-VIS spectral range. Transmission electron microscopy was employed to estimate the particles' size distribution.