Atomic mixing at metal-oxide interfaces by high energy heavy ions

We study the atomic mixing at metal (Bi or Au)/oxide (SiO2 or Al2O3) interfaces under 150-200 MeV heavy ion irradiation. Irradiation-induced interface mixing state is examined by means of Rutherford backscattering spectrometry (RBS). For Bi/Al2O3 interfaces, the heavy ion irradiations induce a strong atomic mixing and the amount of the mixing increases with increasing the electronic stopping power for heavy ions. By comparing the results with that for 3 MeV Si ion irradiation, we conclude that the strong atomic mixing observed at Bi/Al2O3 interfaces is attributed to the high-density electronic excitation. On the other hand, for other interfaces (Bi/SiO2, Au/Al2O3 and Au/SiO2), atomic mixing is rarely observed after the irradiation. The dependence of atomic mixing on combinations of irradiating ions and interface-forming materials is discussed.