Optical properties of nanostructured nickel thin films obtained by oblique angle deposition

The article presents a study of the optical properties of nickel nanospirals obtained by glancing angle deposition in order to identify and analyze circular dichroism (CD), a phenomenon in which a material exhibits different light absorption with left- and right- circular polarization. It has been experimentally established that the chiral geometry of nanospirals, formed due to the effect of shading and the speed of rotation of the substrate during deposition, is the cause of a pronounced optical response. The use of scanning electron microscopy (SEM) confirmed the formation of a series of spiral samples with varying pitch and diameter, which connects these morphological parameters with their spectral characteristics. Spectroscopic measurements in the visible range revealed circular dichroism. It is shown that
the specific chiral geometry of nanostructures, formed due to sputtering conditions, leads to differential absorption of left- and right-circularly polarized light in the visible range. The results demonstrate the dependence of the optical response on the morphology of nanospirals, which opens up opportunities for designing metamaterials with specified parameters. The discovered circular dichroism makes such structures promising for use in nanophotonics, the creation of polarization filters, etc. The application of a magnetic field has little effect on the optical properties of the studied samples.