Structure and characteristics of large Fe–O/AlOx/Fe–O tunnel junctions

Abstract

The Fe–O/AlOx/Fe–O tunnel junctions with an area of 1 cm2 were fabricated by reactive magnetron sputtering. The structure and properties of the junctions were studied by scanning electron microscopy, scanning Auger microprobe, x-ray diffraction (XRD), cross-sectional transmission electron diffraction (XTED), atomic force microscopy, vibrating specimen magnetometer, and I–V characteristic. The as-deposited and annealed Fe–O layers have disparate crystalline grain structure. Only bcc–Fe structure is observed in the Fe–O layers through XRD and XTED measurement. Most of the oxygen atoms exist as impurity in the films, and large compressive stress (σ≈−7.9×109 Pa) is induced in the Fe–O layers. The insulating AlOx layer formed by radio-frequency sputtering directly from the alumina target is dense and shows good insulating property.