The growth of metastable fcc Fe78Ni22 thin films on H-Si(100) substrates suitable for focused ion beam direct magnetic patterning

TL;DR

This study demonstrates the successful growth of metastable Fe78Ni22 thin films on hydrogen-terminated silicon substrates with a copper buffer layer, enabling magnetic patterning via focused ion beam irradiation, thus broadening potential applications.

Contribution

It introduces a method to grow metastable Fe78Ni22 films on silicon substrates, expanding their use in magnetic nanostructure fabrication compared to previous copper single crystal substrates.

Findings

Fe78Ni22 films can be grown on H-Si(100) with Cu buffer.

Films undergo magnetic and structural phase transformations upon ion irradiation.

Substitution of copper substrates enables broader application possibilities.

Abstract

We have studied the growth of metastable face-centered-cubic, non-magnetic Fe78Ni22 thin films on silicon substrates. These films undergo a magnetic (paramagnetic to ferromagnetic) and structural (fcc to bcc) phase transformation upon ion beam irradiation and thus can serve as a template for direct writing of magnetic nanostructures by the focused ion beam. So far, these films were prepared only on single crystal Cu(100) substrates. We show that transformable Fe78Ni22 thin films can also be prepared on a hydrogen-terminated Si(100) with a 130-nm-thick Cu(100) buffer layer. The H-Si(100) substrates can be prepared by hydrofluoric acid etching or by annealing at 1200{\deg}C followed by adsorption of atomic hydrogen. The Cu(100) buffer layer and Fe78Ni22 fcc metastable thin film were deposited by thermal evaporation in an ultra-high vacuum. The films were consequently transformed in-situ by 4keV Ar+ ion irradiation and ex-situ by a 30 keV Ga+ focused ion beam, and their magnetic properties were studied by magneto-optical Kerr effect magnetometry. The substitution of expensive copper single crystal substrate by standard silicon wafers dramatically expands application possibilities of metastable paramagnetic thin films for focused ion beam direct magnetic patterning.