Three-Dimensional Nanopatterning of Magnetic Materials
Shengrong Ye and R. Lloyd Carroll
Department of Chemistry, West Virginia University, Morgantown, WV 26506
Photolithographic techniques provide a direct route to patterning objects in two
dimensions on flat surfaces. However, most of the lithographic techniques are diffraction
limited – patterns smaller than ~200nm are difficult to produce reliably. Reliable three
dimensional techniques are similarly limited by optical resolution. Self-Assembly of
nanoscale structures to form patterns has been proposed as a solution to overcome the
challenges of conventional lithography, but are rarely, arguably never, defect free, and
are not typically coherent over long ranges (100s to 1000s of microns) necessary to make
them useful. These challenges can be overcome by building handles into the system to
facilitate driving the self-organizing system towards a low-energy minimum.
In this work, efforts to form such systems, using magnetic composite materials and
shaped magnetic fields as "handles" will be described. Self-organization of simple rod
structures with nanoscale dimensions into oriented arrays using magnetic fields as a
driver for a curable magnetic nanocomposite has been achieved and will be described. To
achieve high fidelity uniformly patterned structures with arbitrary dimensions, we are
exploring the use of nanosphere lithography and near-field phase-shift photolithography
to produce hexagonal and more complex patterns of magnetic islands. These islands will
then direct the influence of magnetic fields to direct the magnetic materials to specific
locations and spacings. Mechanisms of formation of the rods and arrays will also be
discussed
15m
10m
Figure 1 – Scanning Electron Micrographs of rod arrays self-organized under the
influence of a magnetic field. The array on the left has an avg. rod diameter of 722±80
nm and avg. spacing of 2.4±0.4 m. The inset shows the radial distribution function for
the array. The array on the right is composed of rods with an avg. diameter of 1000±30
nm and avg spacing of 3.2±0.2 m.