Nanobumps and nanoholes have been formed in gold and silver films with various thicknesses on a dielectric substrate by strongly focused single nanosecond pulses of a Nd:YAG laser. An apertureless dielec tric fiber probe and an aspherical lens with a numerical aperture of 0.5 were used to focus laser radiation into a diffraction limited spot on the surface of gold and silver films, respectively. Atomic force and electron microscopy studies have demonstrated that the shape and dimension of nanostructures, as well as the thresh old parameters of laser radiation for their formation, are determined by the thickness of a modified film ("size effect") and by the duration of a laser pulse owing to the lateral heat conduction in films (nonlocal energy deposition effect). Mechanisms of the dynamic formation of such structures in metallic films by nanosecond laser pulses due to phase transformations of their material have been discussed.

Single-pulse microprocessing of a steel surface with a variable pulse width (0.3–12.3 ps) and a wavelength of 515 nm was performed. The morphology of the craters was visualized by a scanning electron microscope and an optical profilometer. The nonmonotonic behavior of ablation thresholds with a minimum at  ≈1.5 ps, due to achieving the electron–phonon relaxation time of the absorbed energy in the steel was revealed. It is shown that, with an increase in the pulse width in the considered width range, the efficiency of the ablation decreases by a factor of 2, which is explained by the partial transition from the phase explosion to the surface evaporation.

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A novel approach was proposed and demonstrated to fabricate in a controllable manner alloyed colloidal Ag/Au nanoparticles with predetermined stoichiometry from thin, magnetrondeposited bilayered (Ag/Au) films of variable layer thickness by their nanosecond laser ablation in water. The optical properties of the obtained colloidal solutions were systematically analyzed, both experimentally and theoretically, indicating the alloyed character of the bimetallic nanoparticles as a monotonic 'red' spectral displacement of the localized plasmon resonance position, as well as gradual variation of its amplitude and width with increasing gold content in the bilayered films. Transmission electron microscopy and energy dispersive xray spectroscopy support the alloyed rather than fragmentary character of the bimetallic nanoparticles, with the increasing gold content resulting in an increasing average nanoparticle size. This approach appears to be highly promising for the controllable ondemand fabrication of different bi and polymetallic nanoparticles with predetermined stoichiometries.

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