A combined x-ray specular reflectivity and spectroscopic ellipsometry study of CeO2/yttria-stabilized-zirconia bilayers on Si(100) substrates

The combination of x-ray specular reflectivity (XRSR) with spectroscopic el lipsometry measurements constitutes a new and useful tool for the character ization of thin films, We illustrate this statement with measurements made on CeO2/yttria-stabilized-zirconia (YSZ) bilayers deposited onto silicon su bstrates, CeO2 being on top of YSZ. CeO2/YSZ buffer layers are notably appr opriate for the epitaxial growth of high temperature superconducting films or all sorts of oxide films on Si substrates, XRSR was used to measure the thickness of each layer of CeO2./YSZ bilayers deposited on silicon. The res ults showed remarkably well defined and numerous oscillations, thus reveali ng low interface and surface roughness. Using a modeling and fitting proces s with the measured data, we extracted an interface roughness between YSZ a nd CeO2 in the range of 0.2-0.5 nm and a CeO2 surface roughness of 1.9 nm ( root mean square values). Moreover the simulation curve fitted very well if a thin amorphous SiO2 layer was assumed to lie at the interface between YS Z and Si. The optical properties of YSZ and CeO2 in the 0.25-1.7 mu m wavel ength range, which are strongly dependent upon the composition and depositi on parameters, were determined by the combination of spectroscopic ellipsom etry measurements with XRSR results, and comparisons with the literature we re made. Overall our results showed very good quality of the CeO2/YSZ oxide bilayers grown on silicon substrates. (C) 1998 American Institute of Physi cs. [S0021-8979(98)07421-0].