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

Paper MI+EM-WeM5
Pinhole Decoration in Magnetic Tunnel Junctions

Wednesday, October 27, 1999, 9:40 am, Room 618/619

Session: Spin-Dependent Tunneling and Transport
Presenter: D. Allen, University of Alabama
Authors: D. Allen, University of Alabama
R. Schad, University of Alabama
G. Zangari, University of Alabama
I. Zana, University of Alabama
D. Yang, University of Alabama
M.C. Tondra, Nonvolatile Electronics
D. Wang, Nonvolatile Electronics
Correspondent: Click to Email
Magnetic tunnel junctions are of interest for their possible applications in magnetic sensors and nonvolatile memory devices. The possibility of local shortcuts in the insulating layers of magnetic tunnel junctions, known as pinholes, can cause malfunctions in these devices. The reduction of insulator thicknesses will make this problem more severe. The ability to image pinholes could lead to further development of magnetic tunnel junctions. The imaging of structures that are not directly observable with imaging is traditionally done by decoration. This can be achieved by exploiting the conductivity of the pinholes. We decorated pinholes in a 1.8nm thick Al@sub2@O@sub3@ layer by electrodeposition of copper. These copper cauliflower-like structures can be imaged by conventional microscopies. Dielectric breakdown could be a source of pinhole creation. Applying 0.5 V for electrodeposition (as used here) would exceed the breakdown threshold for weak points in the insulator. This would create pinholes at points with insulator thickness less than 0.5 nm. This is an opportunity of the method. Upon application of increasing voltage pulses prior to deposition it will allow discrimination of potential breakdown spots as a function of their thickness. The chemical conditions were tailored to avoid damaging the insulator layer or creating new pinholes. This was verified by studying surface roughness (Atomic Force Microscopy), chemical composition (X-ray Photoelectron Spectroscopy) and layering quality (X-ray Diffraction).