No abstract

Interfacial roughness in multilayer films may be random or correlated, i.e., replicated from layer to layer. It is shown that these can be separated and quantified using x-ray diffraction rocking curves and a straightforward analysis. The lateral correlation length along the interfaces can additionally be determined. A quantitative evaluation for W/C multilayers shows that correlated roughness contributes significantly to the total roughness, even at length scales that are surprisingly short, of the order 2–6 nm.

A series of W/C multilayer films sputter deposited on Si( 100) substrates with total thickness ranging from 400 to 6400 A and bilayer period from 20 to 160 A were examined to explore the variation of inter-facial roughness and interfacial roughness correlation with film thickness and period. The films were characterized with x-ray diffractometry. Average inter-facial roughness is obtained from conventional ((328) scans, while information on roughness correlation is extracted from rocking-curve (transverse-profile) analysis. The magnitude of the roughness is found to depend more on bilayer period than on total film thickness. The observations suggest that interfaces retard the evolution of surface roughness and that thin "restarting" layers may be used to control the growth morphology of thin films. 3283

The existence of partially correlated roughness in multilayer thin films is demonstrated using x-ray diffraction diffuse-intensity distribution measurements. The method is generally applicable and produces, in addition to values of magnitudes of interfacial roughness and its lateral correlation length, a measure of the cross correlation between interfaces separated by intermediate ones. A simple phenomenological model can describe roughness in W/C multilayers prepared under standard conditions. A cumulative roughness function is used to show that the wavelength range in which the interfacial roughness predominates in these layers lies between 50 Å and 2000 Å and that the long-wavelength roughness replicates better than the short-wavelength roughness.

The interfacial roughness in multilayer films is described by a model in which the parameters are directly related to those of microscopic growth processes. The height-height correlation function is extracted from this model. Stationary and nonstationary roughness are discussed. The diffuse intensity in diffraction from multilayer films that have various degrees of correlation in roughness between interfaces is calculated. The presence of perfect or partial interfacial roughness correlation can be distinguished unambiguously in the diffusely scattered intensity.