Growth behaviors of SrTiO3/LaAlO3 films could be varied substantially by controlling terminating atomic layers of the substrates. In a film on the LaO-terminated substrate, strain-induced roughening was observed. In a film on the AlO2-terminated substrate, the first atomic layer of the interface seemed to have lots of defects. However, the stress became quickly relaxed, so a SrTiO3 film could be grown in a layer-by-layer mode after a few monolayers. All these observations could be explained in terms of chemical matching between the atomic layers at the interface.
͑Received 22 September 1997͒ Nonspecular x-ray-reflectivity intensities were measured to characterize the interface morphology of a Mo/Si multilayer. Longitudinal off-specular scans and transverse scans at several multilayer peaks and valleys were carried out. For the analysis of the experimental data, a height cross-correlation function between different interfaces was derived for a model multilayer whose interfaces are partially correlated. The parameters related to the interface morphology were obtained by fitting the measured intensities within the distorted-wave Born approximation. The intermixing widths of the graded interfaces, the correlated interface roughness amplitude, and a vertical correlation length were obtained by analyzing the off-specular intensities. ͓S0163-1829͑98͒04615-3͔Specular and nonspecular x-ray reflectivity in grazing incidence angle have been effectively utilized to characterize interface morphology. While specular reflectivity yields a density profile perpendicular to the sample surface, nonspecular scattering yields lateral interface structures. Sinha et al. formulated a distorted-wave Born approximation ͑DWBA͒ formalism for a single rough surface to analyze x-ray-reflectivity intensities near the critical angle. 1 The extension of the DWBA calculation to layered structures were done by Holý and Baumbach 2 and others 3,4 for epitaxially grown heterostructures with relatively sharp interfaces. Though the intermixing of elements between layers is another crucial factor determining interface characteristics, especially in magnetic metallic multilayers, a DWBA analysis for nonspecular reflectivity intensities of multilayers with graded interfaces has not been reported earlier, to our knowledge.In this work we carried out nonspecular x-ray-reflectivity studies of a Mo/Si multilayer which has graded interfaces. The experimental data have been analyzed within the DWBA to extract the parameters related to its interface morphology, including the intermixing widths. A simple model is presented to describe partially correlated interfaces in multilayers. The cross-correlation function, which has been widely used without derivation in order to characterize partially correlated interfaces of epitaxially grown multilayers, 4-6 is derived from the model, and has been applied to analyze our nonspecular x-ray-reflectivity data.During deposition process of multilayers, a height profile h m (r ជ ) of the mth interface with respect to the average interface plane z m is conformally transferred to the (mϩ1)th interface, while uncorrelated random noise generates a deviation from perfect correlated interfaces. For partially correlated interfaces, the interface profile can be related to the adjacent one by the following recursive equation: 7where r ជ is the lateral coordinate in the average interface plane. ĥ m (r ជ ) and m (r ជ ) refer to the normalized profile of the mth interface and normalized deviation from the perfect replication of the (mϪ1)th interface, respectively. The first term on the right-hand ...
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Diffuse x-ray reflectivity intensities were measured to characterize interface morphologies of Mo/Si multilayers with and without interleaved carbon thin layers. Parameters related to the interface morphologies can be obtained by fitting the measured intensities within the distorted wave Born approximation in such a way that intermixing widths of graded interfaces, correlated interface roughness amplitudes and vertical correlation lengths are obtained. The interface parameters of Mo/Si and Mo/C/Si/C multilayers are compared for as-grown samples and annealed ones.
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