MEASUREMENT OF THE LATTICE-PARAMETERS IN THE INDIVIDUAL LAYERS OF SINGLE-CRYSTAL SUPERLATTICES

A method for determination of the lattice parameters, parallel to the sample surface as well as normal to the sample surface, in the individ ual layers of single-crystalline superlattices is derived. The method is based on simulations of low angle reflectivity measurements in comb ination with x-ray diffraction reciprocal space mapping. The number of unknown simulation parameters is reduced from three to one, namely th e layer thickness of one of the layers which constitutes the bilayer p eriod, if compared to techniques based only on simulations of the high angle diffraction pattern. The technique is demonstrated by character izing a single-crystalline Mo/V(001) superlattice grown by dual-target magnetron sputtering onto MgO(001) substrates. The lattice parameters of the tetragonally distorted layers were a(Mo)=0.309 nm, c(Mo)=0.319 nm, a(V)=0.305 nm, and c(V)=0.298 nm which correspond to a misfit dis location density of similar to 0.056 dislocations per nm at each inter face and a relaxation of similar to 1/3 of the coherency strain. The l attice parameters obtained by the method were confirmed by comparing a kinematical calculation of the high angle Mo/V(002) theta-2 theta dif fraction pattern (using the obtained values as input parameters) with the experimentally determined pattern. (C) 1995 American Institute of Physics.