Microstructure formation during the annealing of iron nitrides

The thermal metastability of iron nitride was exploited to fabricate thin-film microstructures applicable to left-handed metamaterials. A granular thin film containing dispersed iron particles was prepared by post-annealing an rf-sputter-deposited Fe0.5Al0.5N thin film with a wurtzite-type structure in a nitrogen atmosphere at 450 °C. The obtained samples showed magnetic resonance in the microwave region. Laser direct writing was also applied in a nitrogen atmosphere to an rf-sputter-deposited Fe0.7Al0.3N thin film. 200 μm-wide, 300 Ω cm iron metal lines were drawn in a host nitride film of approximately 2 kΩ cm. Combining and optimizing the above negative permeability and permittivity values should provide left-handed materials with a negative refractive index.

Optical microscopic observation of laser drawn Fe lines on a FeN/AlN thin film.Figure optionsDownload as PowerPoint slideResearch highlights▶ Microstructures were formed in iron nitride thin film for left-handed metamaterials. ▶ Iron granules dispersed thin film was obtained by thermal annealing of Fe0.5Al0.5N film. ▶ In Fe0.7Al0.3N film, iron metal lines were drawn by the laser direct writing.