Microstructure of sputter-deposited Co/Si multilayer thin films

This article presents the results of an investigation by transmission electron microscopy, electron diffraction, x-ray diffraction, and x-ray reflectivity of sputter-deposited Co/Si multilayers. Structures with individual layer thicknesses above about 5 nm retain elemental regions and also some interfacial mixing, but below this thickness very significant intermixing occurs with alloy formation through interdiffusion. Changes in composition in these interfacial regions reveal themselves as a change in atomic arrangement from crystalline to amorphous phases. This can be induced either by increasing the Si or reducing the Co layer thickness, resulting in alloy formation over a limited distance with a variable average composition. A simple model is proposed to explain the observed microstructural changes.