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(Fabrication and Characterization of Modulated Nanowires and Nano-Contact)

Author: TangWei
Tutor: GuoGuangHua
School: Central South University
Course: Physics
Keywords: modulated anodic aluminum oxide modulated nanowires electrodeposition nano-contact magnetism
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Type: Master's thesis
Year: 2013
Downloads: 5
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Abstract


Abstract:Magnetic nanowires have important application in Spintronic devices such as magnetic memory and logic devices. Nanowires with modulated diameters and multilayer nanowires were electrodeposited by using anodic aluminum oxide template, and the magnetism properties were characterized. Further more, single nanowire contact electrode device was fabricated.1. Our team studied the effect of the types of electrolyte on the pore diameters based on asymmetric anodic oxidation method. The results show that the pore diameters formed in sulphuric acid、oxalic acid and phosphoric acid is small、medium and large respectively. Porous anodic alumina with modulated pore diameters was prepared by alternate anodization of aluminum in several different electrolytes.2. Using porous anodic alumina as template, cobalt and nickel nanowires with modulated diameters were electrodeposited. The X-ray Diffraction(XRD) reveals that Ni nanowires have single face centre cube structure and well preferred orientation along (220) direction, while Co nanowires have hexagonal-closed-packed structure and orientation along (100) and (110) direction. The hysteresis loops of nanowires array were measured by physical properties measurement system at different temperatures. The results show that the magnetic anisotropy of Ni nanowires is derived from shape anisotropy and the coercivity change litter with temperatures. While magnetic anisotropy of Co nanowires is determined by the competition between magnetocrystalline anisotropy and shape anisotropy, thus result in the coercivity of Co nanowires increase as the decrease of temperature.Co/Cu Multilayer nanowires were electrodeposited. The XRD analysis implied that the phase of Co layer has face centered cubic phase and hexagonal phase.The magnetic properties was characterized.3. Multiprobe single nanowires electrode was fabricated by optic lithography and electron beam lithography. The contact of nanowires and electrode was test. The results reveal that the contact is ohmic, but the contact resistance is over10KΩ It could be reduced by Ar plasma before metal deposition and the contact resistance of some samples is as low as1KΩ. The huge contact resisitance is derived from intrinsic nature oxide on the surface of nanowire.

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