Abstract. The influence of the sputtering gas pressure and substrate bias voltage on the structure, optical properties and hardness of magnetron deposited thin carbon films is investigated. The structure variations were studied by transmission electron microscopy, and ultramicrohardness tester was used to estimate the Vickers hardness of the films. The optical constants and associated functions were determined from transmittance and reflectance data analysis obtained by spectrophotometrical measurements at near-to-normal incidence in the visible and ultraviolet photon energy region. A strong dependence of the morphology and film structure on the bias voltage and sputtering gas pressure is found. The absolute values of the optical constants, optical band gap and energy loss function of the carbon films are discussed in terms of the theoretical considerations for the amorphous semiconductors. It is also obtained that the microhardness of the thick 2-2.5 μm films ranges from 2 GPa to about 11 GPa and shows a trend to increase (i) with the decrease of the sputtering gas pressure and (ii) with the increase of the negative substrate bias potential at given discharge current and pressure.

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