Tungsten-containing amorphous carbon films deposited by pulsed vacuum arc

Abstract

Amorphous carbon (a-C) films with a wide range of W concentrations have been produced by mixing C+ and Wn+ plasma streams originated in filtered cathodic arc plasma sources. Adhesion of these films to silicon substrates was very high, and was achieved by atomically mixing the film and the Si at the interface. The deposition of the tungsten-doped amorphous carbon films was carried out at room temperature, and the energy of the depositing ions was in the range of 100–6keV. The films were characterized by TEM, XRD, XPS, RBS and Raman spectroscopy. Small additions of W to amorphous carbon significantly decrease the magnitude of the compressive stresses that are present in these films. The corresponding decrease in hardness with increasing W content was not nearly as significant. Film hardness varied between 63GPa (with 1at.% W) and 20GPa (the bulk value for WC) and depended not only on the W content but also on the depositing ion energy. At W contents between 20 and 50at.%, the film consisted of crystalline WC dispersed in an amorphous C matrix. At W content below 20at.%, the WC present in the film was amorphous, and the film consisted then of mixtures of a-WC and a-C.