| Research Abstract |
The goal of this research project was to find novel quantum-mesoscopic phenomena, unobservable in the past nanostrutures fabricated by semiconductor nano-technologies, in unique nanostrucures fabricated by nano-porous Alumina membranes. The following things were successfully observed.
1.Coulomb blockade (CB) in an array of single nano-tunnel junctions/high-impedance quantum-wires. We connected Ni-nanowires with electron-electron interaction following Altshuler's theory and multi-walled carbon nanotubes (MWNT) with localization, phase interference effect of electron waves, to single nano-tunnel junctions. CB, different between the structures, was successfully observed. We pointed out that phase fluctuation energy caused by electron-electron interaction and charging energy were the key for the Ni-wires/single junctions system. In contrast, we provided a question, "Is energy dissipation in high-impedance external environment actually indispensable to yield CB in single junction systems? ", in MWNTs/single junction systems. It was because localization, yielding CB, was an elastic phenomenon.
2.Successful fabrication of MWNTs into Alumina membranes. We found that phase interference of electron waves in the MWNTs was very sensitive to the impurities on the top end of the MWNTs with only 5% in volume ratio. It was firstly found that spin-orbit interaction in heavy-mass impurities (Au, Pt) changed the weak localization in MWNTs to the anti localization.
3.Successful observation of abrupt magnetoresistnce (MR) jumps originated from macroscopic quantum tunneling (MQT) of magnetic domain walls, in Ni-nanowires., by detailed measurements. Correlation of the MQT with weak localization was also firstly investigated.
4.MR oscillation measured among the Ni-quantum wires and dependence of coecivity on Ni-wire diameter.
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