DOI: 10.1002/adfm.200500365 Multifaceted and Nanobored Particle Arrays Sculpted Using Colloidal Lithography** By Dae-Geun Choi, Se Gyu Jang, Sarah Kim, Eungsug Lee, Chang-Soo Han, and Seung-Man Yang* 1. Introduction Particle arrays with ordered two-dimensional (2D) patterns fabricated from colloidal self-assemblies are of practical signifi- cance for applications in biosensors, [1,2] nanoscale display de- vices, [3] stamps for microcontact printing and micromolding, [4,5] microlenses for projection photolithography, [6] magnetic mem- ory devices, [7] porous membranes, [8] and nanostructured tem- plates for new functional materials. [9,10] Colloidal lithography, which uses colloidal arrays as litho- graphic masks or templates, is an inexpensive, inherently paral- lel, high-throughput nanofabrication technique. [11–13] Recently, colloidal lithographic patterning via reactive-ion etching (RIE) has been developed for the fabrication of non-spherical-parti- cle arrays, [14,15] non-close-packed particle arrays, and masks for selective deposition or etching of functional materials. [7,16,17] Meanwhile, non-spherical-particle arrays using a colloidal layer can provide new types of functionalities not attainable from spherical particles. For example, non-spherical particles can be used as a 2D particle array for antireflection surfaces, [18] trian- gular metal structures [1] and nanophotonic crescent structures for ultrasensitive detection of biomolecules, [19] and non-spheri- cal building blocks for 2D or three-dimensional (3D) photonic crystals. [20] In particular, Fujimura et al. modified the morphol- ogy of a self-assembled, 2D single layer (monolayer) of poly- styrene (PS) microspheres by RIE and measured the reflec- tance or transmittance of the modified monolayer as a function of the RIE time. [18b] They found that not only was the photonic band blue-shifted but the intensity of the maximum reflectance peak was reduced with the etching time. This result provides a possible route to the fine-tuning of stop bands (both positions and widths) of colloidal layers by changing the size of the building blocks during the RIE etching procedure. To date, most studies have used single and double layers of colloidal particles in the colloidal-lithography process. [9–13,18b,16–20] Re- cently, it was demonstrated that multilayered colloidal assem- blies can be used as colloidal masks or templates in colloidal li- thography. [14,21] Also, we recently reported a simple method for fabricating 2D and 3D arrays of non-spherical particles of var- ious shapes and patterns via anisotropic RIE. [14] In this case, the top layer of the colloidal array acted as a mask, owing to the relative shadowing effect in the anisotropic RIE process. The size and shape of the resulting particle arrays and inter- stices between particles could be easily controlled by adjusting the crystal orientation, the number of colloidal layers, and the RIE conditions. [14] Van Duyne and co-workers utilized colloi- dal lithography in combination with angle-resolved etching (or deposition) to produce size-tunable triangular structures. [22,23] More recently, we developed a new strategy wherein an inverse opaline structure was utilized as a lithographic mask in colloi- dal lithography. [15] Using this approach, arrays of patterned particles with pores of three- or fourfold symmetry could be successfully fabricated. These patterned particles with regular holes can be applied to the fabrication of functional composite particles, including Pt-incorporated PS–Pt composite particles. Adv. Funct. Mater. 2006, 16, 33–40 © 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 33 – [*] Prof. S.-M. Yang, S. G. Jang, S. Kim Department of Chemical and Biomolecular Engineering Korea Advanced Institute of Science and Technology 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea) E-mail: smyang@kaist.ac.kr Dr. D.-G. Choi, Dr. E. Lee, Dr. C.-S. Han Nano-Mechanical Systems Research Center Korea Institute of Machinery & Materials 171 Jang-dong, Yuseong-gu, Daejeon 305-343 (Korea) [**] This work was supported by the Center for Nanoscale Mechatronics and Manufacturing of the 21st Century Frontier Research Program (M102KN010002-05K1401-00214). Partial support from the National R&D Project for Nano Science and Technology of the Ministry of Commerce, Industry and Energy, the BK21 program, and the CUPS- ERC are also acknowledged. Supporting Information is available on- line from Wiley InterScience or from the author. A novel method of fabricating multifaceted and nanobored particle arrays via colloidal lithography using colloidal-crystal layers as masks for anisotropic reactive-ion etching (RIE) is reported. The shape of the sculpted particles is dependent on the crystal orientation relative to the etchant flow, the number of colloidal layers, the RIE conditions, and the matrix (or mask) structure in colloidal lithography. Arrays of non-spherical particles with sculpted shapes, which to date could not otherwise be produced, are fabricated using a tilted anisotropic RIE process and the layer-by-layer growth of a colloidal mask. These non- spherical particles and their ordered arrays can be used for antireflection surfaces, biosensors, and nanopatterning masks, as well as non-spherical building blocks for novel colloidal crystals. In addition, polymeric particles with patterned holes of controlled depths obtained by the present method can be applied to the fabrication of functional composite particles. FULL PAPER