Patterning self-assembled FePt nanoparticles

We describe a potential way to extend the ordered domain of self-assembled FePt nanoparticles. The FePt particles, with an average diameter of 3 nm, were prepared by simultaneous thermal decomposition of Fe(CO)(5) and chemical reduction of Pt(acac)(2) and then were dispersed in a mixture of hexane and octane. When self-assembling on a plain silicon wafer, FePt nanoparticles formed ordered hexagonal arrays in a range of tens to a few hundred nanometers. A silicon wafer with patterned holes of a photoresist film, made using UV-Iithographing technique, was used as a template to direct the stacking direction of the FePt nanoparticles. The FePt dispersion was dropped on the patterned holes of the photoresist film. After being heat-treated at 100degreesC for 30 min under vacuum condition, the photoresist was stripped out by dipping the sample in acetone. The patterned disks, with an average diameter of 2.0 mum and a height of 250 nm, of self-assembled FePt nanoparticles were examined using SEM and Auger mapping. Their magnetic properties were measured using AGM. The Auger electrons of neither Fe LMM nor Pt MNN could be detected from the sample, which indicated the adsorption of oleic acid and oleylamine on the surface of FePt nanoparticles. The coercivity of patterned FePt significantly increased with the annealing temperature above 600degreesC. (C) 2003 Elsevier B.V. All rights reserved.