XRD CHARACTERIZATION OF MULTILAYERED SYSTEMS

An innovative procedure has been devised for the processing of X-ray d iffraction data from thin films and layered samples, using the convent ional Bragg-Brentano geometry. Conventional phase analysis procedures always consider the sample as a homogeneous set of crystals with rando m orientation; this assumption can lead to severe errors when studying layered samples with thickness less than the penetration depth of the X-rays. Two effects have been considered: the transparency of the lay ers, that limits the diffracted intensity, and the absorption of the o uter layers, that reduces both the incident and the diffracted intensi ty. Both effects can be described by functions connecting the layer th ickness and the absorption coefficient of the present phases to the to tal diffracted intensity. Adopting this strategy, the thickness of eac h layer and its phase composition can be refined together with the oth er structural parameters of interest, such as lattice parameters, crys tallite size, microstrain and preferred orientation. The methodology h as been tested on samples obtained by physical vapor deposition and by thermal oxidation of metal surfaces.