Swift Heavy Ion Beam-Based Nanopatterning Using Self-Assembled Masks
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1020-GG02-06
Swift Heavy Ion Beam-Based Nanopatterning Using Self-Assembled Masks Jens Jensen1, Ruy Sanz2, Marek Skupinski1, Manuel Hernandez-VÈlez3, Gˆran Possnert1, and Klas Hjort1 1 Department of Engineering Sciences, Uppsala University, The ≈ngstrˆm Laboratory, Box 534, Uppsala, SE-751 21, Sweden 2 Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, Madrid, 28049, Spain 3 Departamento de Fisica Aplicada, Universidad Autonoma de Madrid, Madrid, 28049, Spain
ABSTRACT Swift heavy ion beam-based lithography using masks of self-assembled materials has been applied for transferring well-ordered micro- and nanopatterns to rutile TiO2 single crystals. As the induced damage has a high etching selectivity the patterns can be developed in HF with very high contrast. Here we present resulting patterns when using a mask of self-ordered silica spheres. Since the obtained structures are replicas of the mass distribution of the applied mask, the shape and size of resulting structures depend on the geometric configuration of the silica sphere layers. In addition, the resulting pattern can be tuned by varying the applied ion energy and fluence. Direct modifications of the optical properties of TiO2 in a well-defined pattern are also presented. INTRODUCTION Fabricating regular micro- and nanostructures is of great interest due to their potential application in e.g. photonic crystals, data storage, displays, and biological sensors [1,2]. In projection lithography the pattern is defined by a mask, which provides the required template for producing the desired two- or three-dimensional arrays of structures. Swift heavy ion irradiation induces localized material transformation in matter, so-called ion tracks [3], which, compared to e.g. e-beam or photo-lithography, gives a very high contrast between irradiated and non-irradiated regions. In addition, swift heavy ions can transform materials that are otherwise insensitive to electron or photon irradiation, they can induce high aspect ratio structures, and they are only minutely scattered. Combining swift heavy ions with high resolution absorbing masks may thus have potential as a lithography technique for nanotechnology. The advantage with this technique is that it enables, without further processing, directly patterned material modifications. Furthermore, creation of an ordered array of irradiation spots may offer advantages over e.g. the Focused Ion Beam technique, since masking would provide a parallel implantation and patterning technique. The requirements on the mask are very strict, however. The mask should be thick enough to stop or slow down the ions sufficiently and durable enough to withstand high-fluence irradiation or implantation without breaking, disintegrating, or swelling. An interesting option as a lithographic mask is self-assembled materials with highdensity nano- or micro-scale features. One example of a self-assembled template is the porous anodic alumina membrane (PAM) [1,2], see Figure 1(a). Only a few studies on patte
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