Fig. 3-5 (Above)Heavy-ion RBS (Rutherford backscattering) method which allows depth-sensitive structural analysis of the multilayer Heavy ions (16O-ions) reflected from multilayered Nb/Cu have a different energy depending on the mass and position (depth from the surface) of the scattering centers (Nb or Cu). The component back-scattered from Cu further splits into two peaks owing to Cu-isotopes 63Cu and 65Cu. These results demonstrate that the boundaries Nb/Cu are flat plane and without mutual diffusion. (Below)15N-NRA (nuclear resonance analysis) which clarifies the state of hydrogen dissolved in the multilayer Hydrogen atom distribution in multi-layered Nb/Cu is evaluated by measuring emitted gamma-rays (4.43 MeV) from 1H (15N, alpha gamma)12C reaction. This resonance reaction, occurring at ER = 6.385 MeV, is induced with 15N-ion beams of varying energy so as to get non-destructively information on the position of 1H-atoms. The results shown above tell us that hydrogen exists exclusively in the Nb-layers.

Multi-layered Nb/Cu prepared by the molecular beam evaporation technique preserves flat plane boundaries between layers because Nb and Cu do not melt into each other. This meets our expectation for example, for fabricating effective x-ray reflecting materials. For the existing interface-lattice strain to be relaxed, hydrogen atoms are expected to play an important role and it is needed to know the chemical state of hydrogen introduced to clarify its role. By examining the evaporation conditions (substrate temperature and its orientation, etc), we succeeded in preparing a multilayer sample with flat plane boundaries and without mutual diffusion between the layers. Furthermore we have analyzed the depth distribution of hydrogen atoms in the multilayer using the ion-beam resonant nuclear reaction method to find out that the hydrogen exists locally in the Nb layers.

Reference S. Yamamoto et al., Analysis of Hydrogen in Nb/Cu Multilayers using Ion Beams, J. Alloys Comp., 231, 310 (1995).

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