Ion beam mixing effects in the Ar +-irradiated Fe/SiO 2 system

Abstract

Ion beam mixing effects at the metal/insulator interface have been studied by irradiating at room temperature the Fe film/SiO 2 substrate system with 100 keV Ar ions in the fluence range 3 × 10 15 – 1.3 × 10 17 ions/cm 2. The aim of the work was to quantify the ion induced mixing of Fe atoms and clarify the mechanisms involved in the atomic transport processes. SEM analyses of the irradiated surfaces reveal ion beam induced surface morphological modifications as hole formation in the Fe film and Fe island growth. Computer controlled image analyses allowed us to evaluate the Fe coverage at any irradiation fluence, φ , and to introduce a fluence dependent “coverage” factor ƒ(φ) in calculations. The amount of mixed Fe atoms, Q m, has been measured by 1.8 MeV He + Rutherford backscattering, after a chemical etching procedure to remove the unmixed Fe film. The mixing process is well described by the relation Q = Aφ + B√ φ, indicating that both collisional and diffusive mechanisms are effective. The relative influence of these two main mechanisms has been evaluated by determining the coefficients A and B, taking into account the morphological effects expressed by the “coverage” factor ƒ(φ).