Thermal stability of amorphous and crystalline multilayers produced by magnetron sputtering

For the demonstration of the high diversity of different applications of the magnetron sputtering technique in the fabrication of multilayers the production, characterisation and investigations on the thermal stability of epitaxial metallic Mo/V as well as amorphous Si/Ge semiconductor multilayers are presented. It is demonstrated, that combination of low and high angle X-ray diffraction as well as TEM is a very essential tool for the characterisation of the modulated structures and it is also very useful in the investigation of the thermal stability. The experimental results are also compared with numerical calculations made by finite element method for the diffusional homogenisation, controlled by bulk diffusion. It was shown, that in the case of the amorphous Si/Ge system the intermixing is possible in amorphous state, and diffusional stresses do not ca use a significant curvature on the thermal decay curves of the first order peak of the low angle Bragg reflection In(I/I-0) vs t, but they play an important role in the strong porosity formation in the silicon side. Furthermore it was illustrated, that the initial curvature on the In(I/I-0) vs t curve is due to the strong concentration dependence of the intrinsic diffusion coefficients. In epitaxial Mo/V multilayers the thermal behaviour is different. There is a fast transformation of the layered structure into a heterogeneous partly reacted structure, which consists of regions of a reacted Mo(V) alloy and the remaining Mo/V layers. This can not be interpreted by bulk diffusion, but rather by the formation of grain-boundaries inside the Mo layer and probably by a grain-boundary motion induced alloying. (C) 1998 Elsevier Science Ltd. All rights reserved.