Analytical electron microscopy of advanced multilayer structures for magnetic devices

Abstract

Magnetic multilayer structures are key components in devices used for magnetic information storage and sensing. Application in such devices relies on the ability to precisely control the switching characteristics and the magnetic coupling between the layers. The magnetic and transport properties of the device are governed by the composition, structure and thickness of the various layers which make up the multilayer stack as well as the quality of the interfaces between the layers. Advanced analytical electron microscopy techniques are used to investigate the structure and composition of layers in two different types of spin tunnel junction stacks and in perpendicular spin valve stacks. High angle annular dark field scanning transmission electron microscopy imaging combined with electron energy loss spectroscopy spectrum imaging provides rapid coverage of large areas of material along with precise chemical information from specific regions of interest. This combination of techniques is shown to be particularly useful for examining the oxide barrier layers and the extent of any oxidation defects within the layer stacks.