ICMCTF2009 Session H1-1: Nanotube, Nanowire and Nanoparticle Thin-Films and Coatings

The fabrication of thin films with a chiral or helical microstructure has enabled development of a variety of devices that utilize the ability of these coatings to interact with circular polarized light, mimic the periodicity of the diamond lattice, and behave as microscopic springs. Techniques used to make thin films with a helical architecture include serial bideposition¹ and direct laser writing using 2-photon absorption². We use Glancing Angle Deposition (GLAD)³, a physical vapour deposition process that combines the self shadowing effects of oblique incidence vapour flux with precise substrate motion. Recent developments in optimizing architectural control of chiral films and in organic materials by GLAD will be highlighted, in particular for periodic or self-organized arrays. A variety of devices based on chiral thin film structures will be described. Photonic crystal structures based on the square spiral geometry will be presented, including our initial efforts to fabricate inverse square spirals. Other devices such as chiral optical filters, electrically variable nanospring interferometers and thin film chromatograph layers will be described as time permits.

¹I. Hodgkinson and Q.H. Wu, Adv. Mater. 13, 889 (2001).

²K.K. Seet, V. Mizeikis, S. Matsuo, S. Juodkazis, and H. Misawa, Adv. Mater. 17 (2005).

³M.M. Hawkeye and M.J. Brett, J. Vac. Sci. Technol. A25, 1317 (2007).

We demonstrate the formation of self-organized aligned arrays of silver and cobalt nanoparticles; important materials in nanophotonics and nano-scale magnetism. The arrays are produced using a combination of ion beam sputtering and physical vapor deposition. Self-organized periodic ripple patterns with 3 nm amplitude and 35 nm period are formed on silicon and silicon oxide by low-energy ion beam sputtering. These are subsequently used as template substrates for the deposition of metal island films, promoting aligned nucleation and growth of metallic nanostructures. A combinatorial mask deposition technique is utilized to investigate optimal deposition conditions using magnetron sputtering, including deposition rate, film thickness and post-deposition annealing. Investigations into the use of directed velocity plasmas from a pulsed cathodic vacuum arc are also presented. Silver nanoparticle arrays display biaxial localized surface plasmon resonance absorption due to anisotropic interparticle coupling¹. Under appropriate deposition conditions arrays of cobalt nanowires, many microns in length, are formed². A large range of self-organized substrate materials and patterns are available to this simple, scalable technique.

¹T.W.H. Oates, A. Keller, S. Facsko, A. Muecklich, Aligned silver nanoparticles on rippled silicon templates exhibiting anisotropic plasmon absorption, Plasmonics, 2(2) 47-50 (2007).

²T.W.H. Oates, A. Keller, S. Noda, S Facsko, Self-organized metallic nanoparticle and nanowire arrays from ion-sputtered silicon templates, Applied Physics Letters 93 063106 (2008).

Metal nanostructures continue to be the focus of intense research because of their fascinating properties that can be distinctly different form their bulk counterparts, and thus show great promise for a range of applications. One of the key ingredients required for these future applications is the ability to integrate numerous 1D addressable nanostructures through assembly, patterning, and alignment on technologically relevant solid supports, such as semiconductor surfaces. The challenge lies in fabricating large areas of high density metallic nanostructures, with feature sizes below 100 nm, in an economically feasible manner. While photolithography will justifiably remain a core technology with respect to upcoming, sub-65 nm nodes on the semiconductor industry association roadmap, cost considerations for mass manufacturing will be one potential constraint. As a result, there is interest in the development of complementary patterning strategies that involve large scale self-assembly, for use as a soft organic template for metal nanostructure development.¹Here we describe our work towards the use of self-assembled block copolymer nanostructures on technologically relevant semiconductor materials, to produce metallic features, using approaches compatible with existing silicon-based fabrication.

¹Buriak et al, Nature Nano, 2007, 2, 500-506. Buriak et al, ACS Nano, 2, 489-501.