Parallel fabrication of magnetic tunnel junction nanopillars by nanosphere lithography

Abstract

We present a new method for fabricating magnetic tunnel junction nanopillars that uses polystyrene nanospheres as a lithographic template. Unlike the common approaches, which depend on electron beam lithography to sequentially fabricate each nanopillar, this method is capable of patterning a large number of nanopillars simultaneously. Both random and ordered nanosphere patterns have been explored for fabricating high quality tunneling junctions with magnetoresistance in excess of 100%, employing ferromagnetic layers with both out-of-plane and in-plane easy axis. Novel voltage induced switching has been observed in these structures. This method provides a cost-effective way of rapidly fabricating a large number of tunnel junction nanopillars in parallel.

Encoding Information on the Excited State of a Molecular Spin Chain

“…Our junctions are crafted from entire in situ grown FM/molecular layer/FM stacks, thereby preserving nominal structural/magnetic properties, especially at interfaces, using a novel, solvent‐and resist‐free processing technique inspired by nanosphere lithography. [ 34 ] This novel technique is described in Note S4, Supporting Information, and was implemented using 500 nm‐diameter SiO 2 nanobeads. Since intrachain magnetic interactions dominate the very weak interchain interactions in Pc thin films, [ 29 ] and since transport in dielectric devices proceeds along a nanoscale path, [ 35,36 ] it is possible to observe quantum transport effects due to the MSC in a solid‐state mesoscopic device that are similar to those observed in model junctions assembled using a scanning tunneling microscope (STM).…”

Direct visualization of the interfacial position of colloidal particles and their assemblies

“…in drug delivery, 2 emulsion formation and stability, 3 particle assisted wetting, 4,5 and colloidal selfassembly at air-water interfaces. 6,7 The trapping of colloidal particles at the air-water interface 8 and their subsequent organization into highly ordered two-dimensional crystals has been recognized as an important and convenient technology to fabricate functional surface patterns at the nanoscale by an experimentally simple and fast self-assembly process, 7,9,10 with applications in diverse research elds and technologies, including photonics and structural color, [11][12][13] data storage, [14][15][16] control of liquid wetting and repellency, [17][18][19] antireective coatings, 18,20 plasmonic sensing, [21][22][23] near-eld enhancements, [24][25][26] extraordinary transmission of light 27 and light management in solar cells. 28,29 At a more fundamental level, current research efforts take advantage of ordered binary arrangements of nanocrystals to induce cooperative properties not found in single-particle layers; 30,31 to study the effects of nanoscale connement on physical processes such as diffusion; 32,33 to use structured colloidal particles to explore complex assembly structures; 34 to apply anisotropic particles to control drying patterns (i.e.…”

Magnetic nanoarrays on flexible substrates

“…Fabrication of MNP arrays of a few millimeters can be carried out using highly precise and costly techniques, such as e-beam lithography. In contrast, the high-throughput and low-cost technique of nanosphere lithography (NSL) can be used to fabricate large areas of ordered magnetic nanoparticle arrays on rigid or flexible substrates [2][3][4][5][6][7][8][9][10][11][12]. Flexible substrates are important in new application areas that require lightweight and conformal packaging for advanced electronics and electromagnetics functionalities.…”