Electrostatic self-assembly of nanoparticles into ordered nanowire arrays
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K. Giannakopoulos Institute of Materials Science, NCSR Demokritos, 15310 Aghia Paraskevi, Greece
D. Tsoukalasa) Department of Applied Physics, National Technical University of Athens, 15780 Zografou, Greece; and Institute of Microelectronics, NCSR Demokritos, 15310 Aghia Paraskevi, Greece (Received 2 May 2010; accepted 14 July 2010)
A novel nanoparticle self-assembly process is demonstrated. Nanoparticles were fabricated by a DC magnetron sputtering process. A silicon substrate was initially patterned with arrays of peak and valley photoresist structures using inexpensive patterning techniques. When the nanoparticles were deposited onto the prepatterned substrate, due to surface topography induced local increase in the electric field created by the charges on the nanoparticles, the nanoparticles were self-assembled onto the peaks of the structures and formed long nanowire arrays.
I. INTRODUCTION
In recent years, many techniques have been developed for the bottom-up synthesis of nanoparticles and nanowires that are based either on chemical or physical processes. These nanostructures can have potential application in new nanoelectronic, nanophotonic, and nanosensor devices. Despite the progress in methods for growing these low dimensional structures, advancement concerning their controlled placement into specific substrate positions remains quite a challenging task. Any progress achieved along the above lines would enable the exploitation of these nanostructures for the realization of devices and systems using batch manufacturing of high yield technologies. Different approaches have been followed for the precise placement of nanoparticles on exact substrate locations. Koh1 reviews in detail the strategies followed to achieve this goal. These are either based on templateassisted deposition of nanoparticles combined with block copolymer nanostructures2 or on local generation of charge on the substrate using an electron beam,3 an atomic force microscope (AFM) probe,4 or nanoxerography5 to attract charged nanoparticles. Other researchers exploit the self-focusing effects of charged aerosol nanoparticles6 and dielectrophoresis7 to achieve selective placement. More recently, charge effects have also been investigated for placing individual nanoparticles at the center of a pattern that is exposed to an e-beam in its outside area.8 Oates et al.9 reported a method for self-organizing metallic a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2010.16
nanoparticle and nanowire arrays from ion sputtered silicon templates, while Hsu et al.10 reported an electronically self-patterned template fabrication process for the guided growth of nanomaterials or chemical molecules placed in order. Also, Krishnan et al.11 introduced a method for electrostatic self-assembly of charged colloids and macromolecules at the step edges of a patterned SiO2 layer in a fluidic nanoslit. From the techniques reported, it is concluded that for the organization of nanoparticles into ordered arrays, electrica
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