TEM Study on Diffusion Process of NiFe Schottky and MgO/NiFe Tunneling Diodes for Spin Injection in Silicon

• Published in: IEEE transactions on magnetics Vol. 46; no. 6; pp. 2067 - 2069
• Main Authors: Jehyun Lee, Uhrmann, Thomas, Dimopoulos, Theodoros, Bruckl, Hubert, Fidler, Josef
• Format: Journal Article Conference Proceeding
• Language: English
• Published: New York, NY IEEE 01-06-2010; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Annealing; Cross-disciplinary physics: materials science; rheology; Diffusion; Diffusion processes; Diodes; Dispersion; Electron microscopy; Exact sciences and technology; Intermetallics; Iron compounds; Magnesium oxide; Magnetism; Materials science; Nickel; Nickel base alloys; Nickel compounds; Other topics in materials science; Physics; Schottky barriers; Schottky diodes; Silicon; spin injection; Spin polarized transport; Transmission electron microscopy; tunnel diodes; Tunneling; Schottky diodes; Transmission electron microscopy; Schottky barriers; Scattering; Magnesium oxide; Diffusion processes; spin injection; electron microscopy; tunnel diodes; Microstructure; Magnetic properties; Tunnels
• ISSN: 0018-9464; 1941-0069
• DOI: 10.1109/TMAG.2010.2040594

Analytical electron microscopy is employed to study the structural properties of NiFe Schottky diodes and NiFe/MgO tunneling diodes after annealing up to 400° C. Electrical characterization revealed a drop of the barrier height for the Schottky diodes, while the tunneling diodes are thermally stable. From the cross-sectional TEM images of the Schottky diodes, metal diffusion into Si substrate was found. Investigations of the diffusion using energy dispersive spectroscopy and energy filtered transmission electron microscopy revealed that Ni diffused into the Si substrate to form nickel silicide. Moreover, in some cases, the gold capping layer also diffused into the substrate even deeper than Ni. In the case of the tunneling diodes, metal diffusion was inhibited by the presence of MgO.