Highly ordered one-dimensional arrays of nanodots, or nanobeads, are fabricated by forming nanoripples and nanodots in sequence, entirely by ion-beam sputtering (IBS) of Au(001). This demonstrates the capability of IBS for the fabrication of sophisticated nanostructures via hierarchical self-assembly. The intricate nanobead pattern ideally serves to identify the governing mechanisms for the pattern formation: nonlinear effects, especially local redeposition and surface-confined transport, are essential both for the formation and the preservation of the one-dimensional order of the nanobead pattern.

We study the pattern evolution of pre-rippled Au͑001͒ during sputtering by an ion beam that is incident perpendicular to the initial ripple in azimuth at a grazing angle. Prepatterned ripples decay exponentially with time and new ripples develop only after extended flat areas form along the crossing-ion beams. Hence, the superposition of the initial and new ripple patterns does not occur. The kinetic behaviors of new ripples growing on pre-rippled Au͑001͒ by the crossing-ion beams are distinct from those on initially flat Au͑001͒. When comparing the pre-rippled surface to the initially flat surface, the morphological evolution is substantially influenced by enhanced nonlinear effects such as redeposition.

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