Investigation of various phases of Fe–Si structures formed in Si by low energy Fe ion implantation

Abstract

The compositional phases of ion beam synthesized Fe–Si structures at two high fluences (0.50×1017atoms/cm2 and 2.16×1017atoms/cm2) were analyzed using X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The distribution of Fe implanted in Si was simulated using a dynamic simulation code (TRIDYN) incorporating target sputtering effects. The Fe depth profiles in the Si matrix were confirmed with Rutherford backscattering spectrometry (RBS) and XPS depth profiling using Ar-ion etching. Based on XPS binding energy shift and spectral asymmetry, the distribution of stable Fe–Si phases in the substrate was analyzed as a function of depth. Results indicate Fe implantation with a fluence of 0.50×1017atoms/cm2 and subsequent thermal annealing produce mainly the β-FeSi2 phase in the whole thickness of the implanted region. But for the samples with a higher fluence Fe implantation, multiple phases are formed. Significant amount of Fe3Si phase are found at depth intervals of 14nm and 28nm from the surface. Initially, as-implanted samples show amorphous Fe3Si formation and further thermal annealing at 500°C for 60min formed crystalline Fe3Si structures at the same depth intervals. In addition, thermal annealing at 800°C for 60min restructures the Fe3Si clusters to form FeSi2 and FeSi phases.