N. Lymperi, E. Rosolymou, N. Chronopoulou, S. Spanou, E.A. Pavlatou
EastForum 2015-Progress in Functional and sustainable Surface technology (2015), 25-26 June, Lund, Switzerland (oral)
In recent years, nanowire (NW) structures have attracted considerable attention, due to their characteristic chemical and physical properties and their exciting prospects in electronic, photonic and sensors applications. One of the simplest methods to fabricate metal nano-structures, is the so-called template-assisted electroplating which makes use of porous membranes such as anodized aluminium oxide (AAO) disks. Nanoporous alumina is a unique material in several respects. It can easily be prepared by anodic oxidation of aluminium surfaces in polyprotic aqueous media. Using AAO as a template, pore structures with controlled structural properties (pore diameter, modulated pore structure and lengths) can be easily fabricated. We can also achieve uniformity of pore diameters with high pore density (1011 cm-2), cylindrical pore geometry with high aspect ratio and easy dissolution of AAO template without affecting the fabricated nanostructures (metal NWs) confined inside the nanopores. Generally, anodic aluminium oxide (AAO) films are commonly used as templates for manufacturing micro- and nanostructures as they exhibit material properties in nanopore density, arrangement, mechanical strength and chemical stability. The filling of AAO templates with metals, such as copper and nickel, through the process of electrodeposition, has been the subject of several studies in recent years. For instance, copper nanowires exhibit significant potential for applications in modern electronic technology such as in the field of micro/nanoelectronics industry and, in particular, for interconnection in electronic circuits, while nickel nanowires are potential candidates for magnetic storage devices, nanosensors and biomedical applications. The electrochemical deposition method is one of the most feasible processes for manufacturing nanostructured materials or devices, and is relatively inexpensive and simple. It is possible to produce uniform nanowires of the same diameter, length and with uniform density. Additionally, it is a low temperature process that allows nanostructure fabrication with great precision and control and has the capacity to produce nanowires of better quality in terms of purity due to the selectivity of deposition. In the present work both commercially-available AAO templates (Whatman) and selfordered ones were used in order to produce copper and nickel nanowires with desired characteristics. The anodization of aluminium was carried out using an oxalic acid bath and it was a two-step procedure meaning the change of the voltage at a certain time. The nanowires were prepared by the electrodeposition of the metals, from simple sulfate solutions (NiSO4, CuSO4), into the 100nm and 200nm pores of the commerciallyavailable alumina membranes as well as the pores of the self-made templates the diameter of which ranged between 50 nm-80 nm depending on a variety of parameters such as the time of anodization, the type of electrolyte used and the post treatment of the membrane. The electrochemical deposition was carried out under different potential conditions of direct current (DC) and pulse (PED). A detailed analysis of the structural and morphological properties of the Ni and Cu NWs was performed using Field Emission Scanning Electron Microscopy and X-ray Diffraction.