CHARACTERIZATION OF WCX B4C MULTILAYERS SPUTTERED IN REACTIVE ARGON/METHANE ATMOSPHERES/

Two series of WCx/B4C thin film multilayers were produced by d.c. magn etron sputtering in reactive atmospheres of argon with methane additio ns (up to 18%). Thin films of boron carbide and tungsten were also dep osited separately to provide information about the composition of indi vidual layers. The microstructure and chemistry of the sputtered films were characterized using transmission/high resolution electron micros copy, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier tra nsform infrared spectroscopy, secondary ion mass spectroscopy, and ion beam analysis with MeV helium beams. High-resolution imaging showed t hat the structure of the individual layers was completely amorphous, a lthough diffraction (electron and X-ray) indicated well-defined layer ordering. Chemical analysis revealed that, in addition to carbon incor poration, the multilayers contained significant levels of hydrogen. As the methane percentage was increased, the amounts of hydrogen and car bon present increased, and oxygen (which was present in all samples) a nd hydrogen were preferentially incorporated into the boron carbide la yer. The peak reflectivity for Mg K alpha radiation depended on the me thane concentration, with the sample sputtered in a 12% methane atmosp here showing the highest reflectivity of 30%. Annealing of a represent ative multilayer caused substantial hydrogen loss, and a decrease of t he bilayer spacing.