Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

Nanopatterning of different materials is a key requirement in research fields as diverse as magnetism, plasmonics, optics or catalysis. Potential technological applications range from photovoltaics augmented by light trapping [1] to high-sensitivity biomolecule detection using plasmonic signal enhancement [2] and high-speed low-energy information encoding, transmission, and processing based on magnonic crystals [3]. Industrial-scale fabrication of such devices for energy harvesting, medical diagnostics, or information technology requires nanopatterning processes which are fast, facile, cost-effective, scalable, and highly reproducible. A versatile bottom-up nanopatterning approach which can meet these demands is based on ion irradiation of semiconductor surfaces and well-established thin film deposition techniques.

On crystalline semiconductor substrates, nanoscale surface patterns with well-defined lateral periodicity form via the mechanism of reverse epitaxy, i.e. the non-equilibrium self-assembly of vacancies and ad-atoms under ion irradiation [4]. The GaAs(001) surface exhibits highly uniform faceting and therefore lends itself to transferring this pattern regularity to other materials. The nanopatterned GaAs surface can for instance be employed as a substrate for molecular beam epitaxy under grazing incidence, producing arrays of nanodots, nanowires, periodically corrugated thin films, or combinations thereof by geometrical shading. It can also be the basis for hierarchical self-assembly: here, the topography of the GaAs surface provides a preferential direction for the chemical microphase separation in a diblock copolymer thin film. This flat film then serves as a highly ordered chemical template for metal nanostructure growth in a variety of pattern morphologies [5]. The large-area periodically nanopatterned sample systems are especially very well suited for x-ray and neutron scattering experiments.

In this contribution, we outline the reverse epitaxy mechanism and present examples of how the resulting surface nanopatterns can be employed in the fabrication of nanostructure arrays. We hope to stimulate discussion of further applications by emphasizing the simplicity and versatility of this bottom-up approach.

[1] H.A. Atwater and A. Polman, Nature Materials 9 (2010)
[2] J. Vogt et al., Phys. Chem. Chem. Phys. 17 (2015)
[3] D. Grundler, Nature Physics 11 (2015)
[4] X. Ou et al., Nanoscale 7 (2015)
[5] D. Erb et al., Science Advances 1 (2015)