Applied Physics Letters · 2007 · 65 citations · 17 references
Natural SciencesMaterials EngineeringMaterials ScienceCondensed Matter PhysicsElectronic MaterialsInterface ScienceFerromagnetismMagnetic OxidesMagnetic Thin FilmsSuperconducting Thin FilmsSurface PhysicsWide Band Gap SemiconductorsBondingElectron Beam EvaporationElectron Energy-loss SpectroscopyMagnetic Tunnel JunctionsMagnetic Tunneling JunctionsMetal-oxygen BondingTunnel JunctionsTunneling Barriers
Subnanometer‑resolution electron‑energy‑loss spectroscopy examined CoFeB/MgO/CoFeB magnetic tunnel junctions fabricated by electron‑beam evaporation and rf sputtering, before and after annealing. Gap states were detected in the MgO barrier for both growth methods, with rf‑sputtered samples exhibiting more pronounced states, asymmetric oxygen bonding at the interfaces, and significant B‑oxide diffusion; adding an Mg underlayer markedly suppressed BOx formation during annealing.
Electron energy-loss spectroscopy at subnanometer resolution is used to investigate CoFeB∕MgO∕CoFeB magnetic tunnel junctions grown by electron-beam evaporation and radio frequency (rf) sputtering before and after annealing. Gap states were observed in the MgO layer for both growth methods although the rf-sputtered MgO layer showed significantly more gap states. Asymmetry in oxygen bonding between the top and bottom CoFeB∕MgO interfaces was also observed. Moreover, significant amounts of diffused B as BOx were observed in the rf-sputtered MgO layer. A Mg underlayer between the MgO layer and the bottom electrode greatly reduced BOx formation in the barrier upon annealing.
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Giant tunnelling magnetoresistance at room temperature with MgO (100) tunnel barriers
S. Parkin, Christian Kaiser, Alex Panchula et al. · Nature Materials · 2004 · 3.3K citations