Xu et al. Nanoscale Research Letters 2011, 6:525 http://www.nanoscalereslett.com/content/6/1/525 N A N O E X P R E S S Open Access Ultra-long metal nanowire arrays on solid substrate with strong bonding Ju Xu1, Lan Chen2, Alan Mathewson1 and Kafil M Razeeb1* Abstract Ultra-long metal nanowire arrays with large circular area up to 25 mm in diameter were obtained by direct electrodeposition on metalized Si and glass substrates via a template-based method. Nanowires with uniform length up to 30 μm were obtained. Combining this deposition process with lithography technology, micrometre- sized patterned metal nanowire array pads were successfully fabricated on a glass substrate. Good adhesion between the patterned nanowire array pads and the substrate was confirmed using scanning acoustic microscopy characterization. A pull-off tensile test showed strong bonding between the nanowires and the substrate. Conducting atomic force microscopy (C-AFM) measurements showed that approximately 95% of the nanowires were electrically connected with the substrate, demonstrating its viability to use as high-density interconnect. Keywords: nanowire arrays, anodic alumina membranes, electrodeposition, nano-interconnect Introduction Recently, template-based methods have been success- fully adopted for fabrication of metal, semiconductor and polymer nanowire arrays by electrodeposition. These methods have used heavy ion-irradiated polycar- bonate (PC) film or patterned porous anodic alumina membranes (AAM) as the template [1]. AAM has the advantages of high-density, highly ordered pore channels and adjustable pore size compared to the porous PC film. The nanowire arrays obtained can be used for interconnects [2], ultrahigh density capacitors [3], bat- teries [4], memories [5], biosensors [6-8], etc. For all these applications, length and aspect ratio of the nano- wires are the most important parameters to consider. Increasing the length of nanowires will not only enhance the surface area dramatically but also increase the amount of nano-devices grown in one single nanowire [5]. High-aspect ratio metal nanowire arrays with length above 10 μm are usually obtained by using a sputtered metal seed layer on the back of AAM template with fol- low-on electrodeposition [9]. However, the main disad- vantage when using these metal substrates is the lack of possibility for readily integrating the nanostructure array * Correspondence: kafil.mahmood@tyndall.ie 1Tyndall National Institute, University College Cork, Cork, Lee Maltings, Dyke Parade, Cork, Ireland Full list of author information is available at the end of the article with the current microsystem technology. Also, the metal thin film deposited on the back of the AAM is thin and soft and is not a strong physical support [10]. This is a hindrance to achieving uniform length nano- wire arrays with large area coverage because mechanical polishing is required to level the unevenness of the deposited nanowire tops [11]. To address these difficul- ties, there have been many studies where AAMs were fabricated by anodization of evaporated or sputtered alu- minium films on solid substrates, such as Si or glass [12,13]. In order to achieve long nanowires, a thick AAM is required, and this requires the use of a thick Al layer and a long anodization time [14]. The deposition of a thick Al film (above 10 μm) on a solid substrate is neither easy nor cost-effective, especially when consider- ing the quality of the evaporated Al [15] material. How- ever, by using the electron-beam evaporation, an Al film up to 50 μm thick [12] and a length of about 9 μm nanowire has recently been demonstrated [13], most of the publications about nanowire arrays on Si substrates show values below 3 μm [1,9,13,16]. This is due to the high cost of evaporation and thermal-stress which causes detachment during the anodization of the thick Al film. A further disadvantage of using this AAM-Si template created from an evaporated Al film is that the pores of the AAM tend not to be open at the bottom of the channels due to the insulator barrier layer between © 2011 Xu et al; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.