DIFFUSE X-RAY SCATTERING FROM ROUGH INTERFACES IN SPUTTERED W/Si MULTILAYERS. T. H. Metzger, T. Salditt, D. Lott, J. Peisl, Sektion Physik, University of Munich, D-80539 Munich, Germany

Amorphous W/Si multilayers (ML) have been produced by sputtering at varying Ar pressure. The evolving structure of the interfaces is investigated by diffuse x-ray scattering, specular reflectivity measurements and by transmission electron microscopy (TEM). We have adopted the technique of grazing incidence diffraction (GID) to measure the diffuse scattering at small angles, close to the plane of incidence [1]. We demonstrate the advantages of this new technique as compared to off-specular measurements in the plane of incidence. Using x-rays from a synchrotron radiation source (ESRF) we combine triple crystal diffractometry and grazing incidence and exit angles to achieve large lateral momentum transfer together with high resolution. Due to the onedimensional periodic structure of the ML the diffuse scattering intensity is found to be concentrated in "Bragg sheets" through the ML Bragg points.

The decay of the diffuse intensity as a function of lateral momentum transfer is used to determine the height-height self-correlation function. It is found to decay logarithmically (static exponent H=0) for ML grown at low Ar pressure. From the broadening of the "Bragg sheets" along the momentum transfer in growth direction as a function of the lateral momentum transfer the number of interfaces, N, which contribute coherently to the diffuse scattering on a given length scale is obtained. N can be related to the cross-correlation function and thus the dynamic exponent is determined (z=2 for low Ar pressure). The results are discussed in terms of theoretical predictions for various growth models. For low Ar pressure we find height-correlations (exponents H and z) expected from the Edwards-Wilkinson description of growth. For high Ar pressure the roughness morphology changes dramatically and can be described by the Huygens principle growth model [2]. The corresponding values for H and z compare well with our experimental results (H=0.7 and z=1.37). The real structure of the ML is demonstrated by TEM pictures. They support the results from the diffuse scattering study.

[1] T. Salditt, T. H. Metzger, J. Peisl, Phys. Rev. Lett. 73, 2228 (1994)

[2] C. Tang, S. Alexander, R. Bruinsma, Phys. Rev. Lett. 64, 772 (1990)