Paper TF+EM+SE+NS-ThM4
Nanosphere Lithography for Bit Patterned Media
Thursday, November 1, 2012, 9:00 am, Room 10
| Session: |
Nanostructuring Thin Films |
| Presenter: |
A.G. Owen, University of Alabama |
| Authors: |
A.G. Owen, University of Alabama
H. Su, University of Alabama
A.M. Montgomery, University of Alabama
S.M. Kornegay, University of Alabama
S. Gupta, University of Alabama
|
| Correspondent: |
Click to Email |
Nanosphere lithography1-4 has been used to pattern perpendicular magnetic anisotropy Co/Pd multilayers into nanopillars for the first time for bit-patterned media applications. A multilayer stack of Pd10/[Co0.3Pd1]9/Pt5 nm nanolayers was deposited onto a bare silicon wafer. The nanospheres were spin-coated into a uniform monolayer and then reduced in size by plasma ashing in oxygen. The Co/Pd multilayer films were subsequently ion milled into nanopillars using the reduced nanospheres as masks. We tested two ranges of nanosphere sizes, one at about 100 nm, and the other at about 1000 nm. In order to optimize the ashing of the nanospheres, response surface methodology (RSM) was performed to optimize the ashing power and time. It was seen that ashing at low powers of less than 100 W for longer times was more effective than higher powers for short times in shrinking the nanosphere masks without damage. The subsequent ion milling of the Co/Pd films was performed at a near-perpendicular angle to minimize shadowing by the nanospheres. We will discuss some of the complex shapes the nanospheres were patterned into after ashing, and how they translated into variously sized and shaped nanopillars of Co/Pd multilayers after ion milling. Magnetometry was used to characterize the films before and after patterning, showing an improvement in the coercivity and squareness of the media after patterning with nanospheres that were shrunk, but not damaged, by ashing. Micromagnetic simulations using Object Oriented Micromagnetic Framework (OOMF) have been carried out to produce a simulated hysteresis loop which is then compared with the experimental results.
Acknowledgements
The NSF ECCS 0901858 grant, entitled “GOALI: Nanopatterned graded media” is acknowledged for support. Alton Highsmith is acknowledged for support in the UA Microfabrication Facility.
References
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