Nanoanalysis of Interreactions
Structural transformation of oxide tunnel barriers under electrical overload
The project explores the possibilities to analyse the atomic distribution of oxide tunnel barriers by atomprobe
tomography. This method had been proven to yield a local chemical analysis with outstanding spatial
resolution at conductive metallic specimens. The successful application to oxides would be a great progress.
For the experiments Co/Al2O3/NiFe triple layers have been deposited on top of
tungsten substrate tips. The oxide barriers, having a thickness of 1.5 nm, were produced by various techniques,
which let to different oxygen contents inside the barrier. With these thin layers embedded in metal matrix,
indeed successful measurements were possible. Stoichiometric composition were found with sputtering under
at least 10-4mbar partial pressure of oxygen, while the a-posteriori oxidation in an oxygen
atmosphere of natural pressure yielded oxygen depleted barriers.
