Plasma oxidation and magnetoresistance in tunnel junction device

Abstract

We have studied the tunneling junction magnetoresistance (TMR) and oxidation behavior of Al layer in glass\\Co 100 Å\\Al–O x ( t Å)\\Co 30 Å\\Ni–Fe 120 Å tunnel junction devices. The Al–O x thickness was controlled with a different oxidation time and Al thickness. The thin Al layer of 15 Å 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 Å 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–O x 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–O x in an optimum oxidation condition, which was based on the oxidation kinetics of Al.