Size-tuned ZnO nanocrucible arrays for magnetic nanodot synthesis via atomic layer deposition-assisted block polymer lithography

Chun Hao Lin, Srinivas Polisetty, Liam O'Brien, Andrew Baruth, Marc A. Hillmyer, Chris Leighton, Wayne L. Gladfelter

Research output: Contribution to journalArticlepeer-review

18 Scopus citations

Abstract

Low-temperature atomic layer deposition of conformal ZnO on a self-assembled block polymer lithographic template comprising well-ordered, vertically aligned cylindrical pores within a poly(styrene) (PS) matrix was used to produce nanocrucible templates with pore diameters tunable via ZnO thickness. Starting from a PS template with a hexagonal array of 30 nm diameter pores on a 45 nm pitch, the ZnO thickness was progressively increased to narrow the pore diameter to as low as 14 nm. Upon removal of the PS by heat treatment in air at 500 °C to form an array of size-tunable ZnO nanocrucibles, permalloy (Ni80Fe20) was evaporated at normal incidence, filling the pores and creating an overlayer. Argon ion beam milling was then used to etch back the overlayer (a Damascene-type process), leaving a well-ordered array of isolated ZnO nanocrucibles filled with permalloy nanodots. Microscopy and temperature-dependent magnetometry verified the diameter reduction with increasing ZnO thickness. The largest diameter (30 nm) dots exhibit a ferromagnetic multidomain/vortex state at 300 K, with relatively weakly temperature-dependent coercivity. Reducing the diameter leads to a crossover to a single-domain state and eventually superparamagnetism at sufficiently high temperature, in quantitative agreement with expectations. We argue that this approach could render this form of block polymer lithography compatible with high-temperature processing (as required for technologically important high perpendicular anisotropy ordered alloys, for instance), in addition to enabling separation-dependent studies to probe interdot magnetostatic interactions.

Original languageEnglish (US)
Article number1379
Pages (from-to)1379-1387
Number of pages9
JournalACS nano
Volume9
Issue number2
DOIs
StatePublished - Feb 24 2015

Keywords

  • atomic layer deposition
  • bit patterned media
  • block copolymer
  • magnetic nanodots
  • nanocrucible
  • nanolithography

How much support was provided by MRSEC?

  • Primary

Reporting period for MRSEC

  • Period 1

PubMed: MeSH publication types

  • Journal Article
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

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