Structure of functional Multilayers

GMR Effect of Co/Cu Multilayers

Structural clarification of GMR changes at high temperatures by use of Energy Filtered Transmission Electron Microscopy (EFTEM). This allows color coded maps of the elemental distribution. Here we chose red for Co and green for Cu. The individual layers have 2nm thickness. Research in collaboration with dept. Thin films and nanostructures.

Co/Cu multilayers as deposited.	After annealing at 400°C: Cu break through in Co layer.
After annealing at 600°C: Layer disturbance at the grain boundaries, period doubling of the multilayers.	After annealing at 750°C: Grains of pure Cu and grain with expanded Co layers are formed.

Structure of TMR Layer Systems

Multi layer systems are used as tunneling magneto resistance (TMR) devices. The morphology of the (barrier) layers is visualized by energy filtered TEM. Research in collaboration with dept. Thin films and nanostructures.

Sample with fluctuations of the barrier thickness and warps of the Permalloy layer:

(a) TEM micrograph

(b) Colored ESI image

Sample with break through of the Permalloy layer and oxidation of the Al (and O) layer.

(c) TEM micrograph

(d) Colored ESI image