Determination of the density of ultrathin films using X-ray standing waves

Determination of density of ultrathin films presents a basic challenge for the research of multilayer structures. The commonly used technique of grazing incidence X-ray reflectivity analysis does not provide unique solutions for the layers thinner than 10 nm. Solution to this problem was proposed and explored by measuring the fluorescence yield angular dependence from a thin marker layer, placed above the layer to be characterized. Using simultaneous analysis of grazing incidence X-ray reflectivity and angular dependent fluoresce yields from specially designed and fabricated structures, densities of thin La and LaN layers of 2-6 nm thicknesses have been obtained with approximately 5% precision.