AVS 50th International Symposium
    Nanometer Structures Monday Sessions
       Session NS-MoM

Paper NS-MoM2
In-situ Monitoring of Quantum Conductance in Electrodeposited Magnetic Point Contacts@footnote 1@

Monday, November 3, 2003, 8:40 am, Room 316

Session: Quantum Dots and Nanoscale Devices
Presenter: C.-S. Yang, University of Nebraska, Lincoln
Authors: C.-S. Yang, University of Nebraska, Lincoln
J. Thiltges, University of Nebraska, Lincoln
B. Doudin, University of Nebraska, Lincoln
M. Johnson, Naval Research Laboratory
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The goal of our research is to investigate the magnetoresistance properties of magnetic quantum point contacts. A two-steps fabrication process is used. First, a 50 nm gap between two planar Au electrodes of 1-2 microns widths is patterned using focused ion beam milling. Second, a metallic film is slowly electrodeposited over the electrodes. In-situ measurements of the inter-electrodes impedance monitors the contact resistance during the growth. Keeping electrochemical control of the electrodes ensures optimum purity of the nanocontact, as well as the absence of oxides. Experiments are performed under sweeping magnetic field reaching 1600 Oe amplitude. Quantum conductance steps in Au and Ni point contacts are observed. For Ni, we find that an external field is helpful to observe quantum conductance in multiples of e@super 2@/h, lifting the spin degeneracy. Opening and closure of nanocontacts seldomly occur during the magnetic field sweeping. No significant magnetoresistance was observed for samples of conductance values smaller than 50 e@super 2@/h. Optimizing the measurement speed, we show that no magnetoresistance values larger than 10 % occur when the resistance is stabilized at quantum plateau values during a few magnetic field sweeps. @FootnoteText@ @footnote 1@This research is supported by ONR and NSF MRSEC.