Interdiffusion in nanometer-scale multilayers investigated by in situ low-angle x-ray diffraction

An iii situ low-angle x-ray diffraction technique is used to investigate in terdiffusion phenomena in various metal-metal and metal-amorphous Si nanome ter-scale compositionally modulated multilayers (ML's). The temperature-dep endent interdiffusivities are obtained by accurately monitoring the decay o f the first-order modulation peak as a function of annealing time. Activati on enthalpies and preexponential factors for the interdiffusion in the Fe-T i, Ag-Bi, Fe-Mo, Mo-Si, Ni-Si, Nb-Si, and Ag-Si ML's are determined. Activa tion enthalpies and preexponential factors for the interdiffusion in the ML 's are very small compared with that in amorphous alloys and crystalline so lids. The relation between the atomic-size difference and interdiffusion in the ML's are investigated. The observed interdiffusion characteristics are compared with that in amorphous alloys and crystalline alpha-Zr, alpha-Ti, and Si. The experimental results suggest that a collective atomic-jumping mechanism govern the interdiffusion in the ML's, the collective proposal in volving 8-15 atoms moving between extended nonequilibrium defects by therma l activation. The role of the interdiffusion in the solid-state reaction in the ML's is also discussed. [S0163-1829(99)01516-7].