The influence of adsorbed oxygen at the first interface of single-crystal
Fe(001)/MgO(001)/Fe(001) magnetic tunnel junctions is investigated. Firstly,
the adsorption kinetics of O2 on the Fe(001) surface is studied in the
monolayer regime by X-ray photoelectrons spectroscopy and scanning
tunnelling microscopy experiments. We show that different species exist at
the oxidized surface. The tunnel magneto-resistance of oxygen-doped magnetic
tunnel junctions is found to decrease but remains large even for oxygen
coverages exceeding one monolayer.