Effect of using stencil masks made by focused ion beam milling on permalloy (Ni₈₁Fe₁₉) nanostructures

Abstract

Focused ion beam (FIB) milling is a common fabrication technique to make nanostencil masks which has the unintended consequence of gallium ion implantation surrounding milled features in silicon nitride membranes. We observe major changes in film structure, chemical composition, and magnetic behaviour of permalloy nanostructures deposited by electron beam evaporation using silicon nitride stencil masks made by a FIB as compared to stencil masks made by regular lithography techniques. We characterize the stenciled structures and both types of masks using transmission electron microscopy, electron energy loss spectroscopy, energy dispersive x-ray spectroscopy, magnetic force microscopy and kelvin probe force microscopy. All these techniques demonstrate distinct differences at a length scale of a 1-100 nm for the structures made using stencil mask fabricated using a FIB. The origin of these differences seems to be related to the presence of implanted ions, a detailed understanding of the mechanism however remains to be developed.

TiN-NbN-TiN and Permalloy Nanostructures for Applications in Transmission Electron Microscopy

“…The use of shadow masks (stencils) can potentially solve this problem if sufficient spatial resolution is provided. Stencil lithography has been developed widely in recent years and has been used to achieve sub µm sized apertures and structures [31][32][33][34]. It is based on stencils with nanometer-sized apertures milled into a SiN membrane using, for example, FIB milling.…”

Assembling Magnetic Nanoparticles on Nanomechanical Resonators for Torque Magnetometry

“…Several dry-runs were performed to achieve the desired results using PMMA-950 K A8, PMMA-495 K A8 and PMMA-495 K A2 (depending upon the molecular weight and the viscosity). This process of shape formation was much easier than the stencil mask process [25], and resulted in high resolution, high contrast, and sharp edges and corners [7]. Circles of various sizes were also deposited on the silicon surface as shown in Figure 12 in a magnified view.…”

Epitaxial patterning of thin-films: conventional lithographies and beyond

“…The most widely used material is probably Si 3 N 4 membranes [73]; there are also increasing reports of NSL using inexpensive, easy to fabricate anodic aluminum oxide (AAO) nanostencils [74][75][76][77]. Nanostencil apertures can be defined by laser interference lithography [78], electron beam lithography [79], focused ion beam lithography [80], and local anodic oxidation [81,82]. Nanostencils are usually made very thin, with a thickness around hundreds of micrometers.…”