Characterization of heat-treated CN films fabricated by dual-facing-targetsputtering for soft X-ray multilayer mirrors

The structural characterization of heat-treated CN films fabricated by dual -facing-target sputtering for soft X-ray multilayer mirrors was performed b y means of X-ray diffraction (XRD), Raman spectroscopy (RS) and X-ray photo electron spectroscopy (XPS). The XRD analyses indicate a graphization proce ss in the CN films during thermal annealing. The Raman analyses imply that the primary bonding in the CN films is sp(2). In other words, the formation of the sp(3) bonding in the CN films can be suppressed effectively by dopi ng with N atoms, and thus the thickness expansion resulting from the change s in the density of CN films during annealing can be decreased considerably . This result is also clarified by the increased conductivity measured. The XPS results give the information of the existence of the strong covalent b onding between N and C atoms, which can slow down the tendency of the struc tural relaxation during annealing. These results suggest that CN films suit able for soft X-ray multilayers used at high-temperature environments can b e obtained by reactive dual-facing-target sputtering. With the X-ray diffra ction measurements, we do observe the enhanced thermal stability of CoN/CN multilayers.