Nanojunction Fabrication Using Nanoporous Oxides as Templates

Besides nanotube Y-junction [158], different nanojunctions were fabricated by using nanoporous alumina as template. Al/Al2O3/Ni nanowire and Al/Al2O3/carbon nanotube arrays were prepared by using nanoporous Al2O3 as templates [168-171]. A nanoporous alumina film prepared by electrochemical etching of an Al thin film has an array of nanosized diameter pores located like honeycomb. The nanopores have a straight-line shape perpendicular to Al substrate with a single tunnel barrier attached to each bottom. Ni nanowires were electrochemically deposited within the pores. Alternatively, multiwalled carbon nanotubes were grown within the pores with chemical vapor deposition of C2H2 using a thin layer of Ni as catalyst. Coulomb blockade associated with weak localization in an array of single nano-tunnel junction/multiwalled carbon nanotubes was observed. Magnetoresistance jump in Ni-nanowire array was also found. The nanoporous templates can be extensively used to fabricate other nanowire junctions, such as silicon and germanium nanowire junctions.

Figure 17. Schematic representation of nanotube junctions, where R = (CH2)3NH(CH2)3NH(CH2)3. Reprinted with permission from [163], P. W. Chiu et al., Appl. Phys. Lett. 80, 3811 (2002). © 2002, American Institute of Physics.
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