AVS 46th International Symposium
    Magnetic Interfaces and Nanostructures Technical Group Wednesday Sessions
       Session MI-WeA

Paper MI-WeA1
Hot Electron Attenuation Lengths in Magnetic Multilayers

Wednesday, October 27, 1999, 2:00 pm, Room 618/619

Session: Giant Magnetoresistance
Presenter: R. Lu, University of California, San Diego
Authors: R. Lu, University of California, San Diego
K.L. Kavanagh, University of California, San Diego
C.J. Powell, National Institute of Standards and Technology
P.J. Chen, National Institute of Standards and Technology
F.G. Serpa, National Institute of Standards and Technology
W.F. Egelhoff, Jr., National Institute of Standards and Technology
Correspondent: Click to Email
We are using ballistic electron emission microscopy (BEEM) to measure electron transport across magnetic metal multilayers. Room temperature measurements in air have been carried out on Au/M/Si(100) or Au/M/Au/Si(100) diodes, sputter deposited at 175 or 300K, where M is Co, Fe, Ni, or NiFe(81:19). STM images of the 5nm thick Au surfaces show 10-20nm diameter crystallites, with a typical roughness of 3-6nm, depending on the deposition temperature. Corresponding BEEM images show grain dependent BEEM currents, with uniform contrast across each grain, independent of surface morphology, presumeably a function of the Au or magnetic-metal grain orientation. Averaged BEEM spectra for the Au/M/Si diodes, as a function of magnetic metal thickness (0 - 2nm) show decreasing (Ni or NiFe) or increasing (Co and Fe) BEEM thresholds with increasing metal thickness, indicative of changing magnetic metal/semiconductor interface coverage and/or reactions. Plots of log BEEM current versus M thickness are linear giving hot electron (1-1.5eV) attenuation lengths for Co, Fe, NiFe, and Ni of 2, 5, 8 and 13±2Å, respectively. Magnetic metal sandwich diodes, (Au/M/Au/Si) show comparable attenuation lengths but with smaller BEEM currents, likely the result of greater interface scattering. We are in the process of carrying out BEEM magnetotransport measurements on GMR layers and will report these results at the meeting.