Ion beam induced atomic mixing in a single interface Fe-Ge structure: conversion electron Mossbauer spectroscopy study

Ion beam induced atomic mixing and subsequent thermal reactions are studied in the single interface Fe-Ge structure, using the technique of conversion electron mossbauer spectroscopy (CEMS). Use has been made of a thin ( 50 Å) layer of 57Fe mossbauer isotope (enriched to 95.45%) at the interface of the germanium substrate and a post-deposited 300 λ film of natural iron, to enhance the interface sensitivity of the mossbauer signal. Annealing studies have been carried out at various temperatures upto a maximum of 625°C, to allow for phase transformations. The ion beam mixed samples exhibit the presence of the magnetic FeGe phase along with Fe atoms situated in interstitial positions having a tetrahedrally symmetric environment in Ge. A small fraction of Fe atoms is also found at substitutional sites of the Ge matrix. The as-deposited as well as ion beam mixed composites show significant structural relaxations upon annealing at 350°C, leading to the onset and growth of the Fe enrichment process. When annealed at 625°C for one hour, these composites indicate the segregation of Fe atoms as well as the nucleation and growth of magnetic phases such as FeaGe and Fe5Ge3. Such features are not observed in the case of the as-deposited samples. An attempt is made to understand the similarities and differences in the results obtained in the case of the Fe-Ge system and two other systems viz. Fe-Al and Fe-Si, on which work of similar nature has already been reported

Mossbauer spectroscopic study of ion beam mixing at Fe-Cu interface

Metastable FeCu alloy films have been synthesized by ion beam induced atomic mixing at the Fe-Cu interface. Polycrystalline copper foils coated with 180 λ thick overlayer of iron (enriched to ˜33% in the concentration of 57Fe mossbauer isotope) have been, bombarded with Kr+ ions having energies in the range between 30 keVand 120 keV at a dose of -1016ions/cm2. The as-deposited and ion beam mixed composites have been characterized by using the submicron sensitive technique of conversion electron mossbauer spectroscopy (CEMS). The ion energy dependence of the extent of mixing has been compared with model calculations of energy deposition in interface layers. By deconvoluting the complex mossbauer spectra it has been shown that interface alloy formed by ion mixing exhibits the presence of a random chemical disorder. The ferromagnetic spectral contributions have been analyzed in terms of the presence of one or more copper atoms (acting as magnetic holes in the near neighbour shells of the 57Fe atoms)