Coulomb blockade in nano-junction array fabricated by nonlithographic method

The first observation of the Coulomb blockade (CB) is reported in a single nano-tunnel junction (Al/Al2O3/Ni-nanowire) array prepared in a self-organized porous alumina film without using any lithography. The linear temperature dependence of the zero-bias conductance anomaly observed suggests the presence of the CB. The high resistance Ni-nano wire directly and automatically attached to the single tunnel junction and the high uniformity of array parameters make the emergence of the CB possible in spite of the absent external high resistance block and the high packing density of the tunnel junctions, respectively. The G-V-1/2 curve observed outside the CB-voltage and -temperature regions indicates that the high resistance of Ni-wire originates from the electron-electron (e-e) interaction in a disordered conductor. Our report is, therefore, also the first observation of the CB co-operated by the e-e interaction and of the phase transition between these regimes on temperature and voltage. As one of some interesting problems, which geometry part of the Ni-wire is effective for the parasitic capacitance of the CB is discussed proposing an electric field propagation model. (C) 1998 Elsevier Science Ltd. All rights reserved.