In situ RBS measurements for the effect of swift heavy ion irradiation on metal–insulator interfaces

We have studied the effect of 200 MeV Xe ion irradiation on Bi–Al2O3 and Au–Al2O3 interfaces by means of in situ Rutherford backscattering spectrometry (RBS). For the Bi–Al2O3 interface, we could observe a systematic change in RBS spectrum as a function of Xe ion fluence or the irradiation time. On the other hand, for Au–Al2O3 system, we could not observe any change in RBS spectrum. The experimental result confirmed our previous result that atomic mixing at Bi–Al2O3 interface surely occurs by the Xe ion irradiation. We analyzed the RBS spectra by the simulation software SIMNRA, and discussed the Bi–Al2O3 mixing quantitatively. From the irradiation time dependence of the mixing layer thickness, we estimated the effective diffusion constant for the atomic mixing at Bi–Al2O3 interface. Its value corresponds to the self-diffusion near the melting temperature of Al2O3. The result implies that Bi and Al2O3 are in molten forms during the ion irradiation, resulting in the atomic mixing at Bi–Al2O3 interface.