Fe and N self-diffusion in amorphous FeN: A SIMS and neutron reflectivity study

TL;DR

This study investigates the self-diffusion of iron and nitrogen in amorphous FeN using SIMS and neutron reflectivity, revealing differences in diffusion rates and the influence of structural relaxation below crystallization temperature.

Contribution

It provides the first simultaneous measurement of Fe and N self-diffusion in amorphous FeN using both SIMS and neutron reflectivity techniques, highlighting diffusion mechanisms and structural relaxation effects.

Findings

Fe diffusion is about 100 times slower than N diffusion.

Structural relaxation significantly affects diffusion coefficients below crystallization temperature.

Fe self-diffusion mechanism resembles that in metallic glasses.

Abstract

Simultaneous measurement of self-diffusion of iron and nitrogen in amorphous iron nitride (Fe86N14) using secondary ion mass spectroscopy (SIMS) technique has been done. In addition neutron reflectivity (NR) technique was employed to study the Fe diffusion in the same compound. The broadening of a tracer layer of 57Fe8615N14 sandwiched between Fe86N14 layers was observed after isothermal vacuum annealing of the films at different temperatures in SIMS measurements. And a decay of the Bragg peak intensity after isothermal annealing was observed in [Fe86N14/57Fe86N14]10 multilayers in NR. Strong structural relaxation of diffusion coefficient was observed below the crystallization temperature of the amorphous phase in both measurements. It was observed from the SIMS measurements that Fe diffusion was about 2 orders of magnitude smaller compared to nitrogen at a given temperature. The NR measurements reveal that the mechanism of Fe self-diffusion is very similar to that in metal-metal type metallic glasses. The structural relaxation time for Fe and N diffusion was found comparable indicating that the obtained relaxation time essentially pertain to the structural relaxation of the amorphous phase.