Fabrication of Nanostructured Thin Films Using Porous Alumina Templates
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0951-E09-15
Fabrication of Nanostructured Thin Films using Porous Alumina Templates Aijun Yin, Jin Ho Kim, and Jimmy Xu Engineering, Brown University, 184 Hope Street, Box D, Providence, RI, 02912
ABSTRACT We demonstrate a method for fabricating a variety of nanostructured metallic thin films by using one simple approach based on the use of anodic aluminum oxide (AAO) membrane as masking template. Highly-ordered large-area metallic nanopore- or nanotip-arrays (e.g., Ni, Ag, Au), with various sizes and shapes, were deposited onto AAO membranes through e-beam evaporation. Free standing nano-patterned metallic films were obtained after chemically removing the template and characterized using scanning electron microscopy and electrochemical methods. The nanostructured films will find use in a number of applications, such as plasmonics, electrochemical and biomedical analysis, and catalysis. INTRODUCTION Nanostructured thin films, with two-dimensional highly ordered nanopore or nanorods arrays, have attracted a lot of research interests because of their potential applications in optical, electronic, chemical and electrochemical fields, such as photonic and opto-electronic devices [1,2], gas- or bio-sensors [3, 4], catalysis [5], storage [6] or superconductive media [7], surfaceenhanced Raman scattering (SERS) [8] and cell culture [9]. Several sophisticated approaches have been developed for the fabrication of nanostructured thin films including electron-beam lithography [10], X-ray lithography [11], focused ion beam patterning [12], micro-contact printing [13], self-assembling [14], and template-assisted methods [6-8, 15-25]. In the later case, template-assisted fabrication using anodic aluminum oxide (AAO) has been received much attention [6, 7, 16-25]. An AAO membrane can be obtained by anodizing pure Al foil. When prepared under certain conditions, highly ordered hexagonal pore arrays would form with controlled pore size and channel depth [16]. As compared to colloid crystals [8] or sphere particles [15] which have been used as templates for the fabrication of two-dimensional (2D) highly ordered porous materials, the smaller pore size and higher level of ordering make AAO an attractive template in nanofabrication for materials, such as semiconductors [17, 18], metals [6, 7, 19-23], and oxides [24, 25]. With such a template, many techniques can be applied, such as sputtering [6, 22], electron-beam or thermal evaporation [7, 19, 20], reactive ion etching (RIE) [17, 18], electrodeposition [22, 23], pulsed laser deposition [24], and sol-gel [25]. The properties and applications of the resultant films have been extensively studied as well. For example, magnetization properties of magnetic films containing ordered antidots (arrays of pores) sputtered on anodic alumina substrates have been studied [6], with potential applications in ultrahigh-density recording media. Au nanotube membranes grown by electrodepostion using AAO template were used as shadow masks for generating extended 2-D arrays of metal nanodots via sputter
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