Evaluation of electron/ion sources effect and number of shots on Fe-Ta thin films using plasma focus device

Abstract

The primary objective of this study was to employ the plasma focus (PF) technique to synthesize iron-tantalum (Fe-Ta) thin films while mitigating the reduction of iron content. The investigation focused on two variable parameters: the number of plasma shots and the type of irradiation source (electron or ion). Notably, this work introduced the innovative approach of positioning the iron substrate inside the hollow anode, which distinguishes it from previous experiments. The resulting thin films were characterized comprehensively using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Vickers hardness testing (VHT), and optical microscopy (OM) imaging of Vickers indentations. XRD analyses indicated that the observed stress, strain, and microcracks were minimal and could be considered negligible as the number of electron beam shots increased. Additionally, two distinct intermetallic structures—FeTa and Fe₂Ta—formed during the synthesis process. In all samples, the FeTa phase was found to increase proportionally with the number of shots. SEM observations revealed that higher oxygen content within the films was associated with the formation of improved alloy structures. Consistent with this, EDS and VHT measurements demonstrated that increased oxygen content contributed to enhanced hardness of the films. Importantly, only the ion-irradiated samples exhibited a clear trend of increasing hardness with an increasing number of shots. Overall, the findings indicate that incorporating the iron substrate within the hollow anode enabled the fabrication of ion-irradiated thin films with higher hardness, while maintaining high iron content in electron-irradiated samples.