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Amorphous carbon (a-C) multilayered films consisting of sequential layers rich in sp2 (A) and sp3 (B) content have been developed by magnetron sputtering. We study here the effect of thickness d of the A layer in developing stable thick films with controllable stress and elastic properties. In situ spectroscopic ellipsometry is used to calculate the thickness and the composition of the individual layers. The latter were compared with those obtained by depth profiling X-ray photoelectron spectroscopy, which also provides the different chemical bonding of the multilayers in depth. The stress and hardness of the deposited a-C films were found to be related to the thickness of the Aj layers and the relative ratio dAj/dB of thicknesses. The possible mechanisms for the stress control, stability and enhancement of elastic properties of multilayered a-C films are discussed.
Abstract Femtosecond laser micromachining has excited vivid attention in various industri-
al fields and in medicine owing to the advantages of ultrashort laser pulses compared to
long-pulse treatment.These are mainly the reduction of the laser fluence needed to induce
ablation and the improvement of the contour sharpness of the laser-generated structures.
Recently,special attention was paid to femtosecond laser experiments on nonabsorbing in-
organic dielectrics.This is due to the fact that optical damage in dielectric optical elements
limits the performance of high-power laser systems.Despite the fact that a large variety of
organic polymers can be machined with excimer lasers successfully,the involvement of
thermal processes can lead to an unsatisfactory quality of the structures.Ultrashort,fs-laser
pulses might be an alternative for the treatment of polymers.Therefore,femtosecond laser
machining investigations of dielectrics and polymers are reviewed in this paper.Similarities
and differences of the ablation behavior of both material classes are discussed.The influ-
ence of the bandgap on the ablation threshold in dependence on the pulse duration,the en-
hancement of the machining precision with a shortening of the pulse duration,incubation
phenomena,and morphological features appearing on the surface after femtosecond laser
treatment are mentioned.Possible applications,e.g.,in medicine and biosensors,are de-
scribed.