Plasma oxidation and magnetoresistance in tunnel junction device

We have studied the tunneling junction magnetoresistance (TMR) and oxidation behavior of Al layer in glass/Co 100 A/Al-Ox (t A)/Co 30 A/Ni-Fe 120 A tunnel junction devices. The Al-Ox thickness was controlled with a different oxidation time and Al thickness. The thin Al layer of 15 A showed a rapid variation of TMR ratio with a oxidation time and the maximum TMR ratio of <10% was obtained. The thick Al layer of 25 A showed a slow change of TMR and the higher MR ratio of 16% was obtained at optimum oxidation time. Under various oxidation conditions, we observed the variation of Al-Ox layer by a high resolution transmission electron microscopy. As an oxidation time increase, the initial Al film with some roughness became flat, which was consistent to a variation of a junction resistance. From results, the rough Al layer could be grown to a flat Al-Ox in an optimum oxidation condition, which was based on the oxidation kinetics of Al