Magnetic nanowires and Y-junctions
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Magnetic nanowires and Y-junctions Na hyoung Kim, Bethanie Stadler Electrical and Computer Engineering, University of Minnesota, Minnesota, MN 55455 Abstract Self-assembled nanopore templates were fabricated by anodizing aluminum in several electrolytes under specially selected conditions. The size of the nanopores was controlled, and many sizes were fabricated. Y-junction nanopore templates were also fabricated using a two-step anodization. Magnetic nanowires and Y-junction nanowires were then fabricated by electrochemical deposition of magnetic material into the nanopore templates and Y-junction nanopore templates. The magnetic properties of nanowires were investigated by VSM and compared.
1. Introduction As the size of electronic devices continues to decrease, silicon technology is reaching its limit and the need for new ways to enable us to go beyond this limit is becoming more urgent. Nanostructures, such as nanowires, are attracting increasing attention for fundamental scientific study and for their potential applications in nanoelectronic device. [1-3] As microelectronics were developed, developing devices to increase overall circuit functionality was the primary goal. The goal of nanoelectronics is now to achieve the same functionality of current electronic devices at the nanometer scale. The ability to connect two or more nanostructures is critical to the long-term success of nanoelectronics and circuits. Magnetic nanowires are especially interesting for fundamental magnetic study as well as potential application in magnetoelectronics, magnetic recording, sensors and other magnetic devices. [4-6] Self-assembled nanopores can be used as a template for nanowire growth. [7] These templates allow us to fabricate a straight, parallel nanowires with very high aspect ratios. In addition, the diameter and length of nanowires can be easily controlled in order to meet the application of interest. [8]
2. Experimental Nanopore templates were fabricated by anodizing aluminum in an electrolyte under a several selected conditions. High purity aluminum foil (99.999% pure) with a 2mm thickness was degreased in acetone at room temperature for 10 minutes. Then electrospolishing was performed in mixture of ethanol and perchloric acid at 9oC with 18V. The aluminum foil was then anodized in oxalic acid at 17 oC using 40V. The resulting nanopores had 40nm diameters and were aligned in close-packed hexagonal arrays. The variation in the nanopore diameters was less than 5%. For 20nm diameter nanopores, the aluminum foil was anodized in sulfuric acid at 1 oC using 26V.
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Y-junction nanopore templates used in forming Y-junction nanowires were prepared by a two-step anodization. The aluminum foil was anodized in oxalic acid at 17 oC using 40V for 16hours. This step was needed to enlarge the regions of alignment. The anodized aluminum oxide layer was then etched in a mixture of chromic acid and phosphoric acid at 60 oC. The aluminum foil was anodized again in oxalic acid under the aforementioned conditions for 4hours.
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