Determination of the density of ultrathin La films in La/B(4)C layered structures using X-ray standing waves

Using simultaneous analysis of both the grazing incidence X-ray reflectivity (GIXR) and the angular dependent fluorescence yield from ultrathin layer structures, the densities of thin La and LaN layers of 2-6 nm thickness enclosed by B(4)C layers have been determined with approximately 5% precision. The density of the La layer in these systems is found to be reduced to the bulk La value. This is explained by LaB(6) interlayers formation. The density of LaN layers were similar to the bulk LaN value, which favors this compound as the most energetically stable in LaN/B(4)C layered systems. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim