Observation of ion-irradiation induced diffusion in Pd-Si system using synchrotron radiation X-ray photoelectron spectroscopy

Iwase, Akihiro*; Chimi, Yasuhiro; Ishikawa, Norito   ; Nakatani, Rikizo*; Kato, Yuzaburo*; Fukuzumi, Masafumi*; Tsuchida, Hidetsugu*; Baba, Yuji  

Diffusion of Si atoms in Pd under energetic ion irradiation is studied in Pd-Si thin layer system using synchrotron radiation photoemission spectroscopy. Specimens are prepared by depositing Pd on Si single crystals. The Pd layer thicknesses are 10-300 nm. Before irradiation, we observe photoemission spectra only for Pd, but do not find any trace of Si. After irradiation with 3-MeV Si ions, 1-MeV O ions or 200-MeV Xe ions, we observe an additional photoemission component at the binding energy about 3 eV higher than that of Si 1s bulk component. The experimental result implies that the energetic ion-irradiation induces the diffusion of Si atoms from the Si-Pd interface to the Pd layer surface. The shift of the binding energy from the value for the Si bulk can be interpreted as arising from electron charge transfer from Si to Pd. The dependences of photoemission spectra and ion-irradiation induced diffusion on ion-species and ion-fluence are discussed.