Optimizing large-area nanopillar arrays for magnetic applications

Resumen del trabajo presentado en la 13th European Magnetic Sensors and Actuators Conference (EMSA), celebrada en Madrid (España), del 5 al 8 de julio de 2022
Glancing Angle Deposition with Magnetron Sputtering (GLAD-MS) is an easy and versatile route to fabricate arrays of nanostructures in large areas (cm2 and above) in a single processing step. In a recent work, magnetic nanopillars have been fabricated with vertical or tilted orientation depending on whether the substrate is kept rotating azimuthally during deposition or not, respectively [1]. Although the sputtering target was made of pure iron, the nanopillars were partially oxidized when they were exposed to ambient conditions, therefore the final composition was a mixture of polycrystalline -Fe and Fe2O3 and the saturation magnetization was reduced. The magnetic response was determined mainly by the interplay between the shape anisotropy of individual nanopillars and an extra growth-induced uniaxial anisotropy (associated with an anisotropic surface morphology produced by the glancing angle deposition in the direction perpendicular to the atomic flux) rather than by strong magnetic interactions. In this new work, two improvements have been introduced having in mind future applications. On the one hand, a buffer layer of Ti, 5 nm thick, has been used to enhance the adhesion. On the other hand, a capping layer of Pt, 10 nm thick, prevents the oxidation, as it has been confirmed by grazing incidence X-ray diffraction. These results pave the way for the future use of these nanopillar arrays in several applications, especially in liquid medium.